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ZL2105
Data Sheet February 18, 2009 FN6851.0
3A Integrated Digital DC-DC Converter
Description
The ZL2105 is an innovative power conversion and management IC that combines an integrated synchronous step-down DC-DC converter with key power management functions in a small package, resulting in a flexible and integrated solution. Zilker Labs Digital-DCTM technology enables unparalleled power management integration while delivering industry-leading performance in a tiny footprint. The ZL2105 can provide an output voltage from 0.6 V to 5.5 V from an input voltage between 4.5 V and 14 V. Internal 4.5 A low RDS(ON) synchronous power MOSFETs enable the ZL2105 to deliver continuous loads up to 3 A with high efficiency, and an internal Schottky bootstrap diode further reduces discrete component count. The ZL2105 also supports phase spreading for reduced system capacitance. Power management features such as digital softstart delay and ramp, sequencing, tracking, and margining can be configured by simple pinstrapping or through an on-chip serial port. The ZL2105 uses standard PMBusTM protocol for communicating with other devices to provide intelligent system power management.
Features
Power Conversion
High efficiency 3 A continuous output current Integrated MOSFET switches 4.5 V to 14 V input range 0.54 V to 5.5 V output range (with margin) 1% output voltage accuracy 200 kHz to 2 MHz switching frequency Supports phase spreading Small footprint (6 x 6 mm QFN package)
Power Management
Digital soft start/stop Precision delay and ramp-up Power good/enable Voltage tracking, sequencing, and margining Output voltage/current monitoring Thermal monitor w/ shutdown Non-volatile memory I2C/SMBusTM communication bus PMBus compatible
Applications
Telecom and storage equipment Digital set-top box Industrial supplies 12 V distributed power systems Point of load converters
VDDS CP2 PGND VDDP VDDP PGND
XTEMP
2V5 VDDL
VRA CP1
SDA SCL SALRT
Figure 1. Block Diagram
1
VDR
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VR
ZL2105
Table of Contents
1. Electrical Characteristics ...............................................................................................................................................3 2. Pin Descriptions ............................................................................................................................................................6 3. Typical Application Circuit...........................................................................................................................................8 4. ZL2105 Overview .......................................................................................................................................................10 4.1 Digital-DC Architecture........................................................................................................................................10 4.2 Power Conversion Overview ................................................................................................................................11 4.3 Power Management Overview..............................................................................................................................12 4.4 Multi-mode Pins....................................................................................................................................................12 5. Power Conversion Functional Description..................................................................................................................13 5.1 Internal Bias Regulators and Input Supply Connections ......................................................................................13 5.2 High-side Driver Boost Circuit .............................................................................................................................13 5.3 Low-side Driver Supply Options ..........................................................................................................................13 5.4 Dual Input Supply Configuration..........................................................................................................................14 5.5 Output voltage Selection .......................................................................................................................................15 5.6 Start-up Procedure.................................................................................................................................................15 5.7 Soft Start Delay and Ramp Times.........................................................................................................................16 5.8 Switching Frequency and PLL..............................................................................................................................17 5.9 Component Selection ............................................................................................................................................19 5.10 Current Sensing and Current Limit Threshold Selection ....................................................................................22 5.11 Loop Compensation ............................................................................................................................................22 5.12 Non-linear Response (NLR) Settings..................................................................................................................23 5.13 Efficiency Optimized Drive Dead-time Control .................................................................................................24 6. Power Management Functional Description ...............................................................................................................24 6.1 Input Undervoltage Lockout .................................................................................................................................24 6.2 Power Good (PG) and Output Overvoltage Protection.........................................................................................25 6.3 Output Overvoltage Protection .............................................................................................................................25 6.4 Output Pre-Bias Protection ...................................................................................................................................25 6.5 Output Overcurrent Protection..............................................................................................................................26 6.6 Thermal Overload Protection................................................................................................................................26 6.7 Voltage Tracking...................................................................................................................................................27 6.8 Voltage Margining ................................................................................................................................................28 6.9 I2C/SMBus Communications ................................................................................................................................29 6.10 I2C/SMBus Device Address Selection ................................................................................................................29 6.11 Phase Spreading ..................................................................................................................................................29 6.12 Output Sequencing..............................................................................................................................................30 6.13 Monitoring via I2C/SMBus .................................................................................................................................31 6.14 Temperature Monitoring using the XTEMP Pin.................................................................................................31 6.15 Non-Volatile Memory and Device Security Features .........................................................................................32 7. Package Dimensions....................................................................................................................................................33 8. Ordering Information ..................................................................................................................................................34 9. Related Documentation ...............................................................................................................................................34 10. Revision History........................................................................................................................................................35
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Data Sheet Revision 2/18/2009 www.intersil.com
ZL2105
1. Electrical Characteristics
Table 1. Absolute Maximum Ratings
Voltage measured with respect to SGND. Operating beyond these limits may cause permanent damage to the device. Functional operation beyond the Recommended Operating Conditions is not implied.
Parameter DC Supply Voltage Logic Supply Voltage High Side Supply Voltage High Side Boost Voltage Switch Node Current Internal Drive References Internal 2.5 V Reference Logic I/O Voltage Pin VDDP, VDDS, VDR VDDL BST BST - SW SW VR, VRA V25 EN, MGN, PG, SDA, SCL, SA, SALRT, SS, DLY, SYNC, VTRK, UVLO, V(0,1), ILIM, VSEN, CFG DGND - SGND PGND - SGND VR VRA V25 - - All Soldering, 10 s Comments Optional Value -0.3 to 17 -0.3 to 6.5 -0.3 to 30 -0.3 to 8 4.5 -0.3 to 6.5 -0.3 to 3 -0.3 to 6.5 Unit V V V V A V V V
Sink or Source
Ground Differential MOSFET Drive Reference Current Analog Reference Current 2.5 V Reference Current Junction Temperature Storage Temperature Lead Temperature
0.3 30 150 60 -55 to 150 -55 to 150 300
V mA mA mA C C C
Table 2. Recommended Operating Conditions and Thermal Information Symbol Parameter Input Supply Voltage Range, VDDP, VDDS (See Figure 8) Logic Supply Voltage Range, VDDL Internal Driver Supply, VDR Output Voltage Range
1
Min 4.5 5 3.0 10 0.54 -40 - -
Typ - - - - - - 35 5
Max 5.5 14 5.5 14 5.5 125 - -
Unit V V V V V C C/W C/W
VDDS tied to VR, VRA VR, VRA floating VDDL (optional) VDR VOUT TJ
Operating Junction Temperature Range Junction to Ambient Thermal Impedance Junction to Case Thermal Impedance Notes:
3 2
JA JC
1. Includes margin 2. JA is measured in free air with the device mounted on a multi-layer FR4 test board and the exposed metal pad soldered to a low impedance ground plane using multiple vias. 3. For JC, the "case" temperature is measured at the center of the exposed metal pad. See Figure 4 for thermal derating.
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ZL2105
Table 3. Electrical Specifications
VDDP = VDDS = 12 V, TA = -40C to 85C unless otherwise noted. Typical values are at TA = 25C.
Parameter Input and Supply Characteristics IDDS supply current IDDL supply current IDDS shutdown current IDDL shutdown current VR reference output voltage VRA reference output voltage V25 reference output voltage Output Characteristics Output Current Output voltage adjustment range1 Output voltage setpoint resolution VSEN output voltage accuracy VSEN input bias current Soft start delay duration range2 Soft start delay duration accuracy Soft start ramp duration range Soft start ramp duration accuracy Logic Input/Output Characteristics Logic input bias current (EN,PG,SCL,SDA,SALRT) MGN pin current Logic input low, VIL Logic input OPEN (N/C) Logic input high, VIH Logic output low, VOL Logic output high, VOH Tracking VTRK input bias current VTRK tracking accuracy Notes: Set using SS pin Set using resistor or via I2C Conditions fSW = 200 kHz, no load fSW = 1 MHz, no load fSW = 200 kHz, no load fSW = 1 MHz, no load EN = 0 V, VDDL tied to VRA, No I2C/SMBus activity EN = 0 V, VDDL = 5 V, No I2C/SMBus activity VDD > 5.5 V, IVR < 5 mA VDD > 5.5 V, IVRA < 35 mA IV25 < 50 mA Min - - - - - - 4.5 4.5 2.25 - 0.6 - - -1 - 7 0.007 - 10 0 - -1 -10 -1 - - 2.0 - 2.25 - - 100 Typ 2 5 8 10 0.7 225 5.2 5.2 2.5 - - 10 0.025 - 100 - - 6 - - 100 - - - - 1.4 - - - 110 - Max 3 6 16 20 1 500 5.5 5.5 2.75 3 5.0 - - 1 200 200 500 - 100 200 - 1 10 1 0.8 - - 0.4 - 200 + 100 Unit mA mA mA mA mA A V V V A V mV % FS % A ms s ms ms ms s mA A mA V V V V V A mV
VIN > VOUT Set using resistors Set using I2C/SMBus Includes line, load, temp VSEN = 5.5 V Set using DLY pin or resistor Set using I2C/SMBus
During configuration restore Operating
Multi-mode logic pins IOL 4 mA IOH -2 mA VTRK = 5.5 V 100% Tracking, VOUT - VTRK
1. Does not include margin 2. The device requires approximately 6 ms following an enable signal and prior to output ramp. The minimum settable delay is 7 ms. Table 3 is continued on the following page
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ZL2105
Table 3. Electrical Characteristics (continued)
VDDP = VDDS = 12 V, TA = -40C to 85C unless otherwise noted. Typical values are at TA = 25C.
Conditions Parameter Oscillator and Switching Characteristics Sourcing or Sinking Switch node current, ISW Switching frequency range Predefined settings Switching frequency set-point accuracy Minimum SYNC pulse width External clock source Input clock frequency drift tolerance Maximum duty cycle ISW = 1 A, VGS = 4.7 V RDS(ON) of High Side N-channel FETs ISW=1A, VGS=8.5V, Charge Pump RDS(ON) of Low Side N-channel FETs ISW=1A, VGS=12V Fault Protection Characteristics UVLO threshold range UVLO setpoint accuracy Factory default UVLO hysteresis Configurable via I2C/SMBus UVLO delay Factory default Power good low threshold Factory default Power good high threshold Factory default Power good hysteresis Using pin-strap or resistor 1 Power good delay Configurable via I2C/SMBus Factory default VSEN undervoltage threshold Configurable via I2C/SMBus Factory default VSEN overvoltage threshold Configurable via I2C/SMBus VSEN undervoltage hysteresis Factory default VSEN undervoltage/ overvoltage fault response time Configurable via I2C/SMBus Peak current limit threshold Using ILIM pin or via I2C/SMBus Current limit setpoint accuracy Factory default Current limit shutdown delay Configurable via I2C/SMBus Factory default Thermal protection threshold (junction temperature) Configurable via I2C/SMBus Thermal protection hysteresis Notes: Min - 200 -5 150 -13 90 - - - 3.79 -2 - 0 - - - - 0 0 - 0 - 0 - - 5 0.2 - - 1 - -40 - Typ 3 - - - - - 125 123 114 - - 3 - - 90 115 5 - - 85 - 115 - 5 16 - - 100 5 - 125 - 15 Max 4.0 2000 5 - 13 - 180 140 130 13.2 2 - 100 2.5 - - - 200 500 - 110 - 115 - - 60 4.5 - - 32 - 125 - Unit A kHz % ns % % m m m V % % % s % VOUT % VOUT % ms s % VOUT % VOUT % VOUT % VOUT % VO s s A mA tSW 2 tSW 2 C C C
1. Factory default Power Good delay is set to the same value as the soft start ramp time. 2. tSW = 1/fSW, where fSW is the switching frequency.
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ZL2105
2. Pin Descriptions
Figure 2. ZL2105 Pin Configurations (top view) Table 4. Pin Descriptions Pin Label Type1 1 2 3 4 5 6 7 8 9 10,11 12 13 DGND SYNC SA UVLO ILIM SCL SDA SALRT XTEMP V0, V1 DLY SS PWR I/O, M I,M I,M I,M I/O I/O O I I,M I,M I,M
VTRK I 14 VSEN I 15 NC 16 VDR PWR 17 CP1,CP2 I/O 18, 19 Notes: 1. I = Input, O = Output, PWR = Power or Ground. M = Multi-mode pins.
Description Digital ground. Common return for digital signals. Connect to low impedance ground plane. Clock synchronization input. Used to set switching frequency of internal clock or for synchronization to external frequency reference. Programmable open drain output. Factory default is push-pull Serial address pin used to assign unique SMBus address to each IC. Sets the input undervoltage lockout threshold that disables the device. Sets the current limit threshold level. Serial clock signal for system communications. Serial data signal for system communications. SMBus alert signal. External temperature sensor input. Output voltage select pins. Used to set the output voltage. Soft start delay select pin. Sets the delay from when EN is asserted until the output voltage starts to ramp. Digital soft-start/stop. Sets the ramp period for the output to reach the desired regulation point (after soft-start delay period, if applicable). Track input. Allows the output to track another voltage. Output voltage positive feedback sensing node. No internal connection. Supply pin for internal drivers. Level-shift charge pump for 5 V operation. Connect external capacitor.
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Data Sheet Revision 2/18/2009 www.intersil.com
ZL2105
Table 4. Pin Descriptions (continued) Pin Label Type1 Description PGND PWR Power ground. Common return for internal switching MOSFETs. 20,21 SW I/O Switching node (level-shift common). 22,23 VDDP PWR Bias power for internal switching MOSFETs (return is PGND). 24,25 BST PWR Bootstrap VDD for level-shift driver (referenced to SW). 26 Regulated bias from internal 5V low-dropout regulator (return is PGND). Decouple VR PWR with a 4.7 F capacitor to PGND. 27 Connect 91 resistor between VR and VRA. Regulated 5 V bias for internal analog circuitry (return is SGND). VRA PWR Decouple with a 4.7 F capacitor to SGND. 28 Connect 91 resistor between VR and VRA. Internal logic supply. Connect to VRA or apply a 3.0-5.5 V external supply. Return is VDDL PWR 29 SGND. VDDS PWR IC supply voltage (return is SGND). 30 Regulated bias from internal 2.5 V low-dropout regulator. Decouple with a 10F V25 PWR 31 capacitor. FC I Frequency compensation select pin. Used to set loop compensation. 32 MGN I Signal that enables margining of output voltage. 33 CFG I Configuration pin. Sets switching phase delay and sequencing order. 34 EN I Enable input. Active high signal enables the device. 35 36 ePad PG SGND O PWR Power good output. This pin transitions high 100 ms after output voltage stabilizes within regulation band. Programmable open drain output. Factory default is open drain. Exposed thermal pad. Common return for analog signals; internal connection to SGND. Connect to low impedance ground plane.
Notes: 1. I = Input, O = Output, PWR = Power or Ground. M = Multi-mode pins. Please refer to Section 4.4 "Multi-mode Pins," on page 12.
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ZL2105
3. Typical Application Circuit
The following application circuit represents a typical implementation of the ZL2105.
34
33
32
36
35
31
30
29 17
ePAD (SGND)
12
14
10
11
15
13
16
Figure 3. 12 V to 3.3 V / 3 A Application Circuit (10.8 V UVLO, 10 ms SS delay, 50 ms SS ramp, 12 V used for low-side FET driver)
8
18
V0 V1 DLY SS VTRK VSEN NC VDR CP1
PG EN CFG MGN FC V25 VDDS VDDL VRA
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Data Sheet Revision 2/18/2009 www.intersil.com
ZL2105
For all applications, the ZL2105 must be derated according to the Safe Operating Area (SOA) curves.
Max Conversion Ratio vs Switching Frequency TJ < 125 C
0.95 0.9 0.85 0.8 0.75 0.7 0.65 0.6 0.55 0.5 0.45 0.4 0.35 0.3 0.2
VOUT / VIN
VOUT may not exceed 5.5V at any time
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
1.1
1.2
1.3
1.4
1.5
1.6
1.7
1.8
1.9
2
f SW (MHz)
Figure 4. ZL2105 SOA Curves
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ZL2105
4. ZL2105 Overview
4.1 Digital-DC Architecture
The ZL2105 is an innovative mixed-signal power conversion and power management IC based on Zilker Labs patented Digital-DC technology that provides an integrated, high performance step-down converter for point of load applications. The ZL2105 integrates all necessary PWM control circuitry as well as synchronous 4.5 A N-channel MOSFETs in order to provide an extremely small solution for providing load currents up to 3 A. Its unique PWM loop utilizes an ideal mix of analog and digital blocks to enable precise control of the entire power conversion process with no software required, resulting in a very flexible device that is also very easy to use. An extensive set of power management functions are fully integrated and can be configured using simple pin connections. The user configuration can be saved in an internal non-volatile memory (NVM). Additionally, all functions can be configured and monitored via the SMBus hardware interface using standard PMBus commands, allowing ultimate flexibility. Once enabled, the ZL2105 is immediately ready to regulate power and perform power management tasks with no programming required. Advanced configuration options and real-time configuration changes are available via the I2C/SMBus interface if desired and continuous monitoring of multiple operating parameters is possible with minimal interaction from a host controller. Integrated subregulation circuitry enables single supply operation from any supply between 4.5 V and 14 V with no secondary bias supplies needed. The ZL2105
can also be configured to operate from a 3.3 V or 5 V standby supply when the main power rail is not present, allowing the user to configure and/or read diagnostic information from the device when the main power has been interrupted or is disabled. The ZL2105 can be configured by simply connecting its pins according to the tables provided in the following sections. Additionally, a comprehensive set of tools and application notes are available to help simplify the design process. An evaluation board is also available to help the user become familiar with the device. This board can be evaluated as a standalone platform using pin configuration settings. A WindowsTM-based GUI is also provided to enable full configuration and monitoring capability via the I2C/SMBus interface using an available computer and the included USB cable. Application notes and reference designs are available to assist the user in designing to specific application demands. Please register for My ZL on www.zilkerlabs.com to access the most up-to-date documentation or call your local Zilker Labs sales office to order an evaluation kit.
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ZL2105
4.2 Power Conversion Overview
>
PG EN
INPUT VOLTAGE BUS
VDDL VDDS VDDP
>
VR
MGN ILIM DLY
SS
CFG V(0,1)
VRA
VTRK
POWER MANAGEMENT
NVM
LDO ISENSE
BST
FC SYNC GEN SYNC
DIGITAL DIGITAL COMPENSATOR COMPENSATOR
D-PWM NLR MOSFET DRIVERS
SW
VOUT
PLL ADC ADC RESET REF
+
ISENSE VR
VDR CP1 CHG PUMP CP2 VSEN XTEMP
VDD SALRT SDA SCL SA ADC COMMUNICATION MUX TEMP SENSOR
Figure 5. ZL2105 Block Diagram
The ZL2105 operates as a voltage-mode, synchronous buck converter with a selectable constant frequency PWM control scheme. The ZL2105 incorporates dual low RDS(ON) synchronous MOSFETs to help minimize the required circuit footprint.
is known as the duty cycle D, which is described by the following equation:
V D = OUT V IN
During time D, QH is on and VIN - VOUT is applied across the inductor. As shown in Figure 5, the output voltage is directly applied to the VSEN pin. The VSEN signal is then compared to an internal programmable reference voltage that is set to the desired output voltage level. The error signal derived from this comparison is converted to a digital value with a fast analog to digital (A/D) converter. The digital signal is also applied to an adjustable digital compensation filter, and the compensated signal is used to derive the appropriate PWM duty cycle for driving the internal MOSFETs. The ZL2105 also incorporates a non-linear response (NLR) loop to improve the response time and reduce the output deviation as a result of a load transient. The ZL2105 monitors the power converter's operating conditions and continuously adjusts the turn-on and turn-off timing of the high-side and low-side MOSFETs to optimize the overall efficiency of the power supply.
Data Sheet Revision 2/18/2009 www.intersil.com
Figure 6. Synchronous Buck Converter
Figure 6 illustrates the basic synchronous buck converter topology showing the primary power train components. This converter is also called a step-down converter, as the output voltage must always be lower than the input voltage. The ZL2105 integrates two MOSFETs; QH is the top control MOSFET and QL is the bottom synchronous MOSFET. The amount of time that QH is on as a fraction of the total switching period
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ZL2105
4.3 Power Management Overview
The ZL2105 incorporates a wide range of configurable power management features that are simple to implement with no external components. Additionally, the ZL2105 includes circuit protection features that continuously safeguard the device and load from damage due to unexpected system faults. The ZL2105 can continuously monitor input voltage, output voltage/current, internal temperature, and the temperature of an external thermal diode. A Power Good output signal is also included to enable power-on reset functionality for an external processor. All power management functions can be configured using either pin configuration techniques (see Figure 7) or via the I2C/SMBus interface. Monitoring parameters can also be pre-configured to provide alerts for specific conditions. See Application Note AN13 for more details on SMBus monitoring.
4.4 Multi-mode Pins
Figure 7. Pin-strap and Resistor Setting Examples
Resistor Settings: This method allows a greater range of adjustability when connecting a finite value resistor (in a specified range) between the multi-mode pin and SGND. Standard 1% resistor values are used, and only every fourth E96 resistor value is used so the device can reliably recognize the value of resistance connected to the pin while eliminating the error associated with the resistor accuracy. A total of 25 unique selections are available using a single resistor. I2C/SMBus Method: Almost any ZL2105 function can be configured via the I2C/SMBus interface using standard PMBus commands. Additionally, any value that has been configured using the pin-strap or resistor setting methods can also be re-configured and/or verified via the I2C/SMBus. See Application Note AN13 for more details. The SMBus device address and VOUT_MAX are the only parameters that must be set by external pins. All other device parameters can be set via the I2C/SMBus. The device address is set using the SA pin. VOUT_MAX is determined as 10% greater than the voltage set by the V0 and V1 pins.
Most power management features can be configured using the multi-mode pins. The multi-mode pins can respond to four different connections as shown in Table 5. These pins are sampled when power is applied or by issuing a PMBus Restore command (See Application Note AN13). Pin-strap Settings: Using this method, each pin can take on one of three possible states: LOW, OPEN, or HIGH. These pins can be connected to the VR or V25 pins for logic HIGH settings, as either pin provides a regulated voltage higher than 2 V. Using a single pin one of three settings can be selected, and using two pins the user can select one of nine settings.
Table 5. Multi-mode Pin Configuration Pin Tied To Value LOW < 0.8 VDC (Logic LOW) OPEN No connection (N/C) HIGH > 2.0 VDC (Logic HIGH) Resistor to SGND Set by resistor value
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ZL2105
5. Power Conversion Functional Description
5.1 Internal Bias Regulators and Input Supply Connections 5.2 High-side Driver Boost Circuit
The ZL2105 employs three internal low dropout (LDO) regulators to supply bias voltages for internal circuitry as follows: VR: The VR LDO provides a regulated 5 V bias supply for the MOSFET driver circuits. It is powered from the VDDS pin. A 4.7 F filter capacitor is required at the VR pin. VRA: The VRA LDO provides a regulated 5 V bias supply for the current sense circuit and other analog circuitry. It is powered from the VDDS pin. A small filter capacitor is required at the VRA pin. For single supply operation, this pin should be connected to the VDDL pin so the VRA LDO can be used to power the digital core logic circuitry. V25: The V25 LDO provides a regulated 2.5 V bias supply for the main controller circuitry. It is powered from the VDDL pin. A 10 F filter capacitor is required at the V25 pin. When the input supply (VDDS) is higher than 5.5 V, the VR and VRA pins should not be connected to any other pins. They should have a filter capacitor and a 91 resistor attached as shown in Figure 8. Due to the dropout voltage associated with the VR and VRA bias regulators, the VDDS pin must be connected to the VR and VRA pins for designs operating from a supply below 5.5 V. Figure 8 illustrates the required connections for both cases.
VIN
VDDS VR
The gate drive voltage for the high-side MOSFET driver is generated by a floating bootstrap capacitor, CB (see Figure 6). When the lower MOSFET (QL) is turned on, the SW node is pulled to ground and the capacitor is charged from the internal VR bias regulator through diode DB. When QL turns off and the upper MOSFET (QH) turns on, the SW node is pulled up to VDDP and the voltage on the bootstrap capacitor is boosted approximately 5V above VDDP to provide the necessary voltage to power the high-side driver. An internal Schottky diode is used with CB to help maximize the high-side drive supply voltage.
5.3 Low-side Driver Supply Options
The ZL2105 provides multiple options for powering the internal low-side MOSFET drivers as follows: 12 V Supply: When operating from a 12 V input supply (or any supply 9 V or higher), efficiency can be optimized by operating the low-side MOSFET driver directly from the input supply. Connecting the input supply to the VDR pin (with no external capacitor connected between CP1 and CP2) applies the input supply directly to the low-side driver. This is the simplest method of powering the low-side driver and requires the fewest components. Figure 9 illustrates the required connections for implementing this configuration.
12V
VIN
VDDS VR 91
VR BST
ZL2105
VRA
ZL2105
VRA
4.5V VIN 5.5V
5.5V < VIN 14V
VDDP VDDP
Figure 8. Input Supply Connections
ZL2105
SW SW PGND PGND CP2
VOUT
Note: the internal bias regulators, VR and VRA, are not designed to be outputs for powering other circuitry. Do not attach external loads to either of these pins. The multi-mode pins may be connected to the V25 pin for logic HIGH settings.
12V
Figure 9. Using an External 12 V Supply to Power the Low-side Driver
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ZL2105
Internal Charge Pump: A voltage doubler circuit can be used to optimize efficiency when operating from an input supply that is below 9 V or may occasionally drop below 9 V. The internal charge pump is enabled by connecting a 10 nF capacitor between the CP1 and CP2 pins and a 100 nF capacitor between VDR and PGND. The charge pump provides a low-side driver supply based on the equation below: VCP = (VR - 0.5V) x 2
VDDL VDR
SGND
VDDS
VDDL
VDDS
VRA
Figure 11. Powering the Low-side Driver When VDDS 5.5 V
5.4 Dual Input Supply Configuration
Figure 10. Using the Internal Charge Pump to Power the Low-side Driver
The required connections are shown in Figure 10. Note: when the input supply is always lower than 5.5 V, the VDDS pin must be connected to the VR pin as shown in Figure 11. The resistor between VR and VRA is not required when VDDL and VDDS are tied directly to VR and VRA since this configuration overrides the internal LDOs.
The ZL2105 allows the use of two unique input supplies to enable communication with the device when the primary power rail is not present. Typical applications of this scenario use a 12 V supply as the main power input and either a 3.3 V or 5 V standby supply to power the device during periods when the primary power supply is disabled or not operational. This configuration allows a host controller to communicate with the ZL2105 when the 12 V main supply is not available. Figure 12 shows the typical connections required for this configuration. This figure uses the 12 V supply for powering the low-side driver.
SGND
VDR
CP1
CP1
VDDL VDR
VRA
SGND
VDDS
Figure 12. Dual Input Supply Operation
14
CP1
VRA
Data Sheet Revision 2/18/2009 www.intersil.com
ZL2105
5.5 Output voltage Selection Table 7. Resistors for Setting Output Voltage Index R0 or R1 Index R0 or R1 13 0 34.8 k 10 k 1 14 11 k 38.3 k 2 15 12.1 k 42.2 k 16 3 46.4 k 13.3 k 4 17 14.7 k 51.1 k 5 18 16.2 k 56.2 k 6 19 17.8 k 61.9 k 7 20 19.6 k 68.1 k 8 21 21.5 k 75 k 9 22 23.7 k 82.5 k 10 23 26.1 k 90.9 k 11 24 28.7 k 100 k 12 31.6 k
The output voltage may be set to any voltage between 0.6 V and 5.0 V provided that the input voltage is higher than the desired output voltage by an amount sufficient to prevent the device from exceeding its maximum duty cycle specification. Using the pin-strap method, VOUT can be set to any of nine standard voltages as shown in Table 6.
Table 6. Pin-strap Output Voltage Settings V0 LOW OPEN 0.6 V 0.8 V LOW V1 1.2 V 1.5 V OPEN 2.5 V 3.3 V HIGH
HIGH 1.0 V 1.8 V 5.0 V
The resistor setting method can be used to set the output voltage to levels not available in Table 6. Resistors R0 and R1 are selected to produce a specific voltage between 0.6 V and 5.0 V in 10 mV steps. Resistor R1 provides a coarse setting and resistor R0 provides a fine adjustment, thus eliminating the additional errors associated with using two 1% resistors (this typically adds 1.4% error). To set VOUT using resistors, follow the steps below to calculate an index value and then use Table 7 to select the resistor that corresponds to the calculated index value as follows: 1. Calculate Index1: Index1 = 4 x VOUT (VOUT in 10 mV steps) 2. Round the result down to the nearest whole number.
Example: For VOUT = 1.33 V, Index1 = 4 x 1.33 V = 5.32; From Table 7, R1 = 16.2 k Index0 = (100 x 1.33 V) - (25 x 5) = 8; From Table 7, R0 = 21.5 k
VIN
VDDS VDDP
ZL2105
V0 V1
SW
VOUT 1.33V
R0 21.5k
R1 16.2k
3. Select the value of R1 from Table 7 using the Index1 rounded value from step 2.
4. Calculate Index0: Index0 = 100 x VOUT - (25 x Index1) 5. Select the value of R0 from Table 7 using the Index0 value from step 4.
Figure 13. Output Voltage Resistor Setting Example
The output voltage may also be set to any value between 0.6 V and 5.5 V using the I2C interface. See Application Note AN13 for details.
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5.6 Start-up Procedure Soft Start Delay and Ramp Times
The ZL2105 follows a specific internal start-up procedure after power is applied to the VDD pins (VDDL, VDDP, and VDDS). Table 8 describes the start-up sequence. If the device is to be synchronized to an external clock source, the clock frequency must be stable prior to asserting the EN pin. The device requires approximately 10-20 ms to check for specific values stored in its internal memory. If the user has stored values in memory, those values will be loaded. The device will then check the status of all multi-mode pins and load the values associated with the pin settings. Once this process is completed, the device is ready to accept commands via the I2C/SMBus interface and the device is ready to be enabled. Once enabled, the device requires approximately 7 ms before its output voltage may be allowed to start its ramp-up process. If a softstart delay period less than 7 ms has been configured (using PMBus commands), the device will default to a 7 ms delay period. If a delay period greater than 7 ms is configured, the device will wait for the configured delay period prior to starting to ramp its output. After the delay period has expired, the output will begin to ramp towards its target voltage according to the pre-configured soft-start ramp time that has been set using the SS pin.
5.7
In some applications, it may be necessary to set a delay from when an enable signal is received until the output voltage starts to ramp to its target value. In addition, the designer may wish to precisely set the time required for VOUT to ramp to its target value after the delay period has expired. These features may be used as part of an overall inrush current management strategy or to precisely control how fast a load IC is turned on. The ZL2105 gives the system designer several options for precisely and independently controlling both the delay and ramp time periods. The soft-start delay period begins when the EN pin is asserted and ends when the delay time expires. The soft-start delay period is set using the DLY pin. The soft-start ramp timer enables a precisely controlled ramp to the nominal VOUT value that begins once the delay period has expired. The ramp-up is guaranteed monotonic and its slope may be precisely set using the SS pin. The soft-start delay and ramp times can be set to one of three standard values according to Table 9 and Table 10 respectively.
Table 9. Soft Start Delay Settings DLY Pin Setting Soft Start Delay Time LOW 10 ms OPEN 50 ms HIGH 100 ms
Table 8. ZL2105 Start-up Sequence Step # Step Name Description 1 Power Applied Input voltage is applied to the ZL2105's VDD pins (VDDL, VDDP, VDDS) 2 Internal Memory The device will check for values stored in its internal Check memory. This step is also performed after a Restore command. 3 Multi-mode Pin The device loads values configured by the multi-mode Check pins. 4 Device Ready The device is ready to accept an enable signal. 5 Pre-ramp Delay The device requires approximately 6 ms following an enable signal and prior to ramping its output. Additional pre-ramp delay may be configured using the DLY pin.
Time Duration Depends on input supply ramp time Approx 10-20 ms (device will ignore an enable signal or PMBus traffic during this period) Approximately 6 ms
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Table 10. Soft Start Ramp Settings SS Pin Setting Soft Start Ramp Time LOW 10 ms OPEN 50 ms HIGH 100 ms 5.8 Switching Frequency and PLL
If the desired soft start delay and ramp times are not one of the values listed in Table 9 and Table 10, the times can be set to a custom value by connecting a resistor from the DLY or SS pin to SGND using the appropriate resistor values from Table 11. The value of this resistor is measured upon start-up or Restore and will not change if the resistor is varied after power has been applied to the ZL2105. See Figure 14 for typical connections using resistors.
The ZL2105 incorporates an internal phase-locked loop (PLL) to clock the internal circuitry. The PLL can be driven by an external clock source connected to the SYNC pin. When using the internal oscillator, the SYNC pin can be configured as a clock source for other Zilker Labs devices. The CFG pin is used to select the operating mode of the SYNC pin, configure sequencing, and enable tracking. Table 12 describes the operating modes for the SYNC pin. Section 6.12 "Output Sequencing," on Page 30 describes sequencing and tracking. Figure 15 illustrates the typical connections for each SYNC configuration.
Table 12. SYNC Pin Function Selection CFG Pin SYNC Pin Function LOW SYNC is configured as an input OPEN Auto detect mode SYNC is configured as an output HIGH fSW = 400 kHz
Configuration A: SYNC OUTPUT
Figure 14. DLY and SS Pin Resistor Connections Table 11. DLY and SS Resistor Values DLY or SS RDLY or RSS DLY or SS 0 ms 110 ms 10 k 10 ms 120 ms 11 k 20 ms 130 ms 12.1 k 30 ms 140 ms 13.3 k 40 ms 150 ms 14.7 k 50 ms 160 ms 16.2 k 60 ms 170 ms 17.8 k 70 ms 180 ms 19.6 k 80 ms 190 ms 21.5 k 90 ms 200 ms 23.7 k 100 ms 26.1 k RDLY or RSS 28.7 k 31.6 k 34.8 k 38.3 k 42.2 k 46.4 k 51.1 k 56.2 k 61.9 k 68.1 k
When the SYNC pin is configured as an output (CFG pin is tied HIGH), the device will run from its internal oscillator and will drive the resulting internal oscillator signal (preset to 400 kHz) onto the SYNC pin so other devices can be synchronized to it. The SYNC pin will not be checked for an incoming clock signal while in this mode. Configuration B: SYNC INPUT When the SYNC pin is configured as an input (CFG pin is tied LOW), the device will automatically check for a clock signal on the SYNC pin each time the EN pin is asserted. The ZL2105's oscillator will then synchronize both frequency and phase with the rising edge of the external clock signal. The incoming clock signal must be in the range of 200 kHz to 2 MHz with a minimum duty cycle, and must be stable when the EN pin is asserted. See Table 3 for a complete list of performance requirements for the incoming clock signal.
The soft start delay and ramp times can also be set to custom values via the I2C/SMBus interface. When the SS delay time is set to 0 ms, the device will begin its ramp-up after the internal circuitry has initialized (approx. 6 ms). When the soft-start ramp period is set to 0 ms, the output will ramp up as quickly as the output load capacitance will allow.
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CFG
CFG
CFG
CFG
Figure 15. SYNC Pin Configurations. Table 13. Switching Frequency Selection SYNC Pin Frequency LOW 200 kHz OPEN 400 kHz HIGH 1 MHz Resistor See Table 14
Configuration C: SYNC AUTO DETECT When the SYNC pin is configured in auto detect mode (CFG pin is left OPEN), the device will automatically check for a clock signal on the SYNC pin after enable is asserted. - If a valid clock signal is present, the ZL2105's oscillator will then synchronize both frequency and phase with the rising edge of the external clock signal. The incoming clock signal must be in the range of 200 kHz to 2 MHz with a minimum duty cycle, and must be stable when the EN pin is asserted. See Table 3 for a complete list of performance requirements for the incoming clock signal. - If no incoming clock signal is present, the ZL2105 will configure the switching frequency according to the state of the SYNC pin as listed in Table 13. In this configuration, the SYNC pin is sampled only on startup and will not modify its switching frequency if the SYNC pin is re-configured after start-up (unless the power is recycled).
If the user wishes to run the ZL2105 at a frequency not listed in Table 13, the switching frequency can be set using an external resistor, RSYNC, connected between SYNC and SGND using Table 14.
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Table 14. RSYNC Resistor Values FSW RSYNC FSW 200 kHz 571 kHz 10 k 222 kHz 615 kHz 11 k 242 kHz 667 kHz 12.1 k 267 kHz 727 kHz 13.3 k 296 kHz 889 kHz 14.7 k 320 kHz 1000 kHz 16.2 k 364 kHz 1143 kHz 17.8 k 400 kHz 1333 kHz 19.6 k 421 kHz 1600 kHz 21.5 k 471 kHz 2000 kHz 23.7 k 533 kHz 26.1 k Table 15. Power Supply Requirements RSYN 28.7 k 31.6 k 34.8 k 38.3 k 46.4 k 51.1 k 56.2 k 68.1 k 82.5 k 100 k
Parameter Input voltage (VIN) Output voltage (VOUT) Output current (IOUT) Output voltage ripple (Vorip) Output load step (Iostep) Output load step rate Output deviation due to load step Maximum PCB temp. Desired efficiency Other considerations Range 4.5-14.0 V 0.6-5.5 V 0 to 3 A < 3% of VOUT < Io -- -- 120C -- -- Example Value 12 V 1.2 V 2A 1% of VOUT 50% of Io 10 A/S 50 mV 85C 85% Optimize for small size
The switching frequency can also be set to any value between 200 kHz and 2 MHz using the I2C/SMBus interface. The available frequencies are bounded by fSW = 8 MHz/N, where 4N40. See Application Note AN13 for details. If multiple Zilker Labs devices are used together, connecting the SYNC pins together will force all devices to synchronize with each other. The CFG pin of one device must set its SYNC pin as an output and the remaining devices must have their SYNC pins set as an input. Note: The switching frequency read back using the appropriate PMBus command will differ slightly from the selected value in Table 14. The difference is due to hardware quantization.
5.9 Component Selection
5.9.1 Design Goal Trade-offs
The design of the buck power stage requires several compromises among size, efficiency, and cost. The inductor core loss increases with frequency, so there is a trade-off between a small output filter made possible by a higher switching frequency and getting better power supply efficiency. Size can be decreased by increasing the switching frequency at the expense of efficiency. Cost can be minimized by using throughhole inductors and capacitors; however these components are physically large. To start the design, select a frequency based on Table 16. This frequency is a starting point and may be adjusted as the design progresses.
Table 16. Circuit Design Considerations Frequency Range 200-400 kHz 400-800 kHz 800 kHz - 2 MHz Efficiency Highest Moderate Lower Circuit Size Larger Smaller Smallest
The ZL2105 is a synchronous buck converter with integrated MOSFETs that uses an external inductor and capacitors to perform the power conversion process. The proper selection of the external components is critical for optimized performance. For more detailed guidelines regarding component selection, refer to Application Note AN11. To select the appropriate external components for the desired performance goals, the power supply requirements listed in Table 15 must be known.
5.9.2 Inductor Selection
The output inductor selection process must include several trade-offs. A high inductance value will result in a low ripple current (Iopp), which will reduce output capacitance and produce a low output ripple voltage, but may also compromise output transient load performance. Therefore, a balance must be struck between output ripple and optimal load transient
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performance. A good starting point is to select the output inductor ripple equal to the expected load transient step magnitude (Iostep):
5.9.3 Output Capacitor Selection
I opp = I ostep
Now the output inductance can be calculated using the following equation, where VINM is the maximum input voltage:
LOUT
V VOUT x 1 - OUT V INM = fsw x I opp

Several trade-offs must also be considered when selecting an output capacitor. Low ESR values are needed to have a small output deviation during transient load steps (Vosag) and low output voltage ripple (Vorip). However, capacitors with low ESR, such as semi-stable (X5R and X7R) dielectric ceramic capacitors, also have relatively low capacitance values. Many designs can use a combination of high capacitance devices and low ESR devices. For high ripple currents, a low capacitance value can cause a significant amount of output voltage ripple. Likewise, in high transient load steps, a relatively large amount of capacitance is needed to minimize the output voltage deviation while the inductor current ramps up or down to the new steady state output current value. As a starting point, apportion one-half of the output ripple voltage to the capacitor ESR and the other half to capacitance, as shown in the following equations:
The average inductor current is equal to the maximum output current. The peak inductor current (ILpk) is calculated using the following equation where IOUT is the maximum output current:
I Lpk = I OUT +
I opp 2
Select an inductor rated for the average DC current with a peak current rating above the peak current computed above. In over-current or short-circuit conditions, the inductor may have currents greater than 2X the normal maximum rated output current. It is desirable to use an inductor that still provides some inductance to protect the load and the internal MOSFETs from damaging currents in this situation. Once an inductor is selected, the DCR and core losses in the inductor are calculated. Use the DCR specified in the inductor manufacturer's datasheet:
C OUT =
I opp 8 x f sw x Vorip 2
ESR =
Vorip 2 x I opp
Use these values to make an initial capacitor selection, using a single or capacitor several capacitors in parallel.
PLDCR = DCR x I Lrms
ILrms is given by
2
I Lrms = I OUT +
2
(I )
opp
2
12
where IOUT is the maximum output current. Next, calculate the core loss of the selected inductor. Since this calculation is specific to each inductor and manufacturer, refer to the chosen inductor datasheet. Add the core loss and the ESR loss and compare the total loss to the maximum power dissipation recommendation in the inductor datasheet.
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After a capacitor has been selected, the resulting output voltage ripple can be calculated using the following equation:
5.9.7 CVR Selection
Vorip = I opp x ESR +
I opp 8 x f sw x C OUT
Because each part of this equation was made to be less than or equal to half of the allowed output ripple voltage, the Vorip should be less than the desired maximum output ripple. For more information on the performance of the power supply in response to a transient load, refer to Application Note AN11.
5.9.4 Input Capacitor
This capacitor is used to both stabilize and provide noise filtering for the 5 V reference supply (VR). It should be between 4.7 and 10 F, and be a semi-stable X5R or X7R dielectric ceramic capacitor with a low ESR less than 10 m, and be rated 6.3 V or more. Because the current for the bootstrap supply is drawn from this capacitor, CVR should be sized at least 10X the value of CB so that a discharged CB does not cause the voltage on it to droop excessively during a CB recharge pulse.
5.9.8 CVRA Selection
It is highly recommended that dedicated input capacitors be used in any point-of-load design, even when the supply is powered from a heavily filtered 5 or 12 V "bulk" supply from an off-line power supply. This is because of the high RMS ripple current that is drawn by the buck converter topology. This ripple (ICINrms) can be determined from the following equation:
This capacitor is used to both stabilize and provide noise filtering for the analog 5 V reference supply (VRA). It should be between 2.2 and 10 F, be a semistable X5R or X7R dielectric ceramic capacitor with a low ESR less than 10 m, and be rated 6.3 V or more.
5.9.9 RVR Selection
A 91 resistor should be placed between VR and VRA to reduce noise and help the stability of the VR and VRA regulators over all operating conditions.
5.9.10 Thermal Considerations
I CINrms = I OUT x D x (1 - D )
Without capacitive filtering near the power supply circuit, this current would flow through the supply bus and return planes, coupling noise into other system circuitry. The input capacitors should be rated at 1.4X the ripple current calculated above to avoid overheating of the capacitors due to the high ripple current, which can cause premature failure. Ceramic capacitors with X7R or X5R dielectric with low ESR and 1.1X the maximum expected input voltage are recommended.
5.9.5 Bootstrap Capacitor Selection
In typical applications, the ZL2105's high efficiency will limit the internal power dissipation inside the package. However, in applications that require a high ambient operating temperature the user must perform some thermal analysis to ensure that the ZL2105's maximum junction temperature is not violated. The ZL2105 has a maximum junction temperature limit of 125C, and the internal over temperature limiting circuitry will force the device to shut down if its junction temperature exceeds this threshold. In order to calculate the maximum junction temperature, the user must first calculate the power dissipated inside the IC (PQ) as follows:
PQ = I LOAD 2 R DS(ON )QH DC ) + R DS(ON )QL 1 - DC )
The high-side driver boost circuit utilizes an internal Schottky diode (DB) and an external bootstrap capacitor (CB) to supply sufficient gate drive for the high-side MOSFET driver. CB should be a 47 nF ceramic type rated for at least 6.3V.
5.9.6 CV25 Selection
(
)[(
)(
(
)(
]
The maximum operating junction temperature can then be calculated using the following equation:
T j max = TPCB + PQ x JC
Where TPCB is the expected maximum printed circuit board temperature, and JC is the junction-to-case thermal resistance for the ZL2105 package.
This capacitor is used to both stabilize and provide noise filtering for the 2.5 V internal power supply. It should be between 4.7 and 10 F, and should use a semi-stable X5R or X7R dielectric ceramic with a low (less than 10 m) ESR, and should have a rating of 4 V or more.
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5.10 Current Sensing and Current Limit Threshold Selection Table 18. Current Limit Threshold Settings ILIM RLIM ILIM RLIM 0.2 A 2.6 A 11 k 34.8 k 0.4 A 2.8 A 12.1 k 38.3 k 0.6 A 3.0 A 13.3 k 42.2 k 0.8 A 3.2 A 14.7 k 46.4 k 1.0 A 3.4 A 16.2 k 51.1 k 1.2 A 3.6 A 17.8 k 56.2 k 1.4 A 3.8 A 19.6 k 61.9 k 1.6 A 4.0 A 21.5 k 68.1 k 1.8 A 4.2 A 23.7 k 75 k 2.0 A 4.4 A 26.1 k 82.5 k 2.2 A 4.6 A 28.7 k 90.9 k 2.4 A 31.6 k 5.11 Loop Compensation
It is recommended that the user include a current limiting mechanism in their design to protect the power supply from damage and prevent excessive current from being drawn from the input supply in the event that the output is shorted to ground or an overload condition is imposed on the output. Current limiting is accomplished by sensing the current through the circuit during a portion of the duty cycle. The ZL2105 incorporates MOSFET sensing across the internal low-side MOSFET. The user can select one of the three current limit thresholds using the ILIM pin according to Table 17.
Table 17. Current Limit Selections ILIM Pin Current Limit Threshold LOW 3.0 A OPEN 4.0 A HIGH 4.5 A
If the desired current limit threshold is not available in Table 17, the current limit threshold can be set in 200 mA increments using an external resistor, RLIM, connected between the ILIM pin and SGND using resistor values from Table 18. The current limit threshold can also be set to a custom value via the I2C/SMBus interface. Please refer to Application Note AN13 for further details.
The ZL2105 operates as a voltage-mode synchronous buck controller with a fixed frequency PWM scheme. Although the ZL2105 uses a digital control loop, it operates much like a traditional analog PWM controller. Figure 16 is a simplified block diagram of the ZL2105 control loop, which differs from an analog control loop only by the constants in the PWM and compensation blocks. As in the analog controller case, the compensation block compares the output voltage to the desired voltage reference and compensation zeroes are added to keep the loop stable. The resulting integrated error signal is used to drive the PWM logic, converting the error signal to a duty cycle to drive the internal MOSFETs.
Figure 16. Control Loop Block Diagram
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Table 19. Resistor Settings for Loop Compensation NLR fn Range fsw/60 < fn < fsw/30
Off
fsw/120 < fn < fsw/60
fsw/240 < fn < fsw/120
fsw/60 < fn < fsw/30
On
fsw/120 < fn < fsw/60
fsw/240 < fn < fsw/120
fzesr Range fzesr > fsw/10 fsw/10 > fzesr > fsw/30 fsw/30 > fzesr > fsw/60 fzesr > fsw/10 fsw/10 > fzesr > fsw/30 fsw/30 > fzesr > fsw/60 fzesr > fsw/10 fsw/10 > fzesr > fsw/30 fsw/30 > fzesr > fsw/60 fzesr > fsw/10 fsw/10 > fzesr > fsw/30 fsw/30 > fzesr > fsw/60 fzesr > fsw/10 fsw/10 > fzesr > fsw/30 fsw/30 > fzesr > fsw/60 fzesr > fsw/10 fsw/10 > fzesr > fsw/30 fsw/30 > fzesr > fsw/60
RFC 10 k 11 k 12.1 k 13.3 k 14.7 k 16.2 k 17.8 k 19.6 k 21.5 k 23.7 k 26.1 k 28.7 k 31.6 k 34.8 k 38.3 k 42.2 k 46.4 k 51.1 k
In the ZL2105, the compensation zeros are set by configuring the FC pin or via the I2C/SMBus interface once the user has calculated the required settings. This method eliminates the inaccuracies due to the component tolerances associated with using external resistors and capacitors required with traditional analog controllers. Utilizing the loop compensation settings shown in Table 19 will yield a conservative crossover frequency at a fixed fraction of the switching frequency (fS/20) and 60 of phase margin.
Step 1: Using the following equation, calculate the
The loop compensation coefficients can also be set via the I2C/SMBus interface. Please refer to Application Note AN13 for further details. Refer to Application Note AN16 for further technical details on setting loop compensation.
5.12 Non-linear Response (NLR) Settings
resonant frequency of the LC filter, fn.
fn =
1 2 L x C
The ZL2105 incorporates a non-linear response (NLR) loop that decreases the response time and the output voltage deviation in the event of a sudden output load current step. The NLR loop incorporates a secondary error signal processing path that bypasses the primary error loop when the output begins to transition outside of the standard regulation limits. This scheme results in a higher equivalent loop bandwidth than what is possible using a traditional linear loop. When a load current step function imposed on the output causes the output voltage to drop below the lower regulation limit, the NLR circuitry will force a positive correction signal that will turn on the upper MOSFET and quickly force the output to increase. Conversely, a negative load step (i.e. removing a large load current) will cause the NLR circuitry to force a negative correction signal that will turn on the lower MOSFET and quickly force the output to decrease.
Step 2: Calculate the ESR zero frequency (fZESR).
f zesr =
resistor, RFC.
1 2CRc
Step 3: Based on Table 19, determine the appropriate
The FC pin can be pin-strapped as LOW, OPEN, or HIGH. These three positions are the same as the first three entries in Table 19.
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The NLR loop is enabled through the FC pin by selecting the appropriate resistor value for the loop compensation settings in Table 19. When operating the ZL2105 with a switching frequency greater than 1333 kHz, NLR must be disabled.
5.13 Efficiency Optimized Drive Dead-time Control
6. Power Management Functional Description
6.1 Input Undervoltage Lockout
The ZL2105 utilizes a closed loop algorithm to optimize the dead-time applied between the gate drive signals for the top and bottom MOSFETs. In a synchronous buck topology, potentially damaging currents can flow in the circuit of both top and bottom MOSFETs are turned on simultaneously for periods of time exceeding a few nanoseconds, and system efficiency can be adversely affected if both MOSFETs are turned off for too long. Therefore, it is advantageous to minimize the dead-time to provide peak optimal efficiency without compromising system reliability. The duty cycle of a buck converter is determined to a first-order degree by the input and output voltage ratio. However, non-idealities exist that cause the real duty cycle to extend beyond the ideal value. Dead-time is one of the non-idealities that can be manipulated to improve efficiency. The ZL2105 has an internal algorithm that can continuously adjust the dead-time to optimize duty cycle, thus maximizing efficiency.
The input undervoltage lockout (UVLO) prevents the ZL2105 from operating when the input falls below a preset threshold, indicating the input supply is out of its specified range. The UVLO threshold (VUVLO) can be set between 4.5 V and 10.2 V using the UVLO pin. The simplest implementation is to connect the UVLO pin as shown in Table 20. If the UVLO pin is left unconnected, the UVLO threshold will default to 6.5V.
Table 20. UVLO Pin Settings Pin Setting UVLO Threshold LOW 4.5 V OPEN 6.5 V HIGH 10.2 V
If the desired UVLO threshold is not on of the listed choices, the user can configure a threshold between 3.79 V and 13.2 V by connecting a resistor between the UVLO pin and GND by selecting the appropriate resistor from Table 21. VUVLO can also be set to any value between 3.79 V and 13.2 V via the I2C/SMBus interface.
Table 21. UVLO Resistor Values UVLO UVLO RUVLO 3.79 V 7.42 V 23.7 k 4.18 V 8.18 V 26.1 k 4.59 V 8.99 V 28.7 k 5.06 V 9.90 V 31.6 k 5.57 V 10.90 V 34.8 k 6.13 V 12.00 V 38.3 k 6.75 V 13.20 V 42.2 k RUVLO 46.4 k 51.1 k 56.2 k 61.9 k 68.1 k 75 k 82.5 k
Once an input undervoltage fault condition occurs, the device can respond in a number of ways as follows: 1. Continue operating without interruption 2. Continue operating for a given delay period, followed by shutdown if the fault still exists. The device will remain in shutdown until instructed to restart. 3. Initiate an immediate shutdown until the fault has been cleared. The user can select a specific number of retry attempts.
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6.2 Power Good (PG) and Output Overvoltage Protection
The ZL2105 provides a Power Good (PG) signal that indicates the output voltage is within a specified tolerance of its target level and no fault condition exists. By default, the PG pin will assert if the output is within +15%/-10% of the target voltage. These limits may be changed via the I2C/SMBus interface. A PG delay period is defined as the time from when all conditions for asserting PG are met and when the PG pin is actually asserted. This feature is commonly used instead of an external reset controller to signal the power supply is at its target voltage prior to enabling any powered circuitry. By default, the ZL2105 PG delay is set equal to the soft-start ramp time setting. Thus if the soft-start ramp time is set to 10ms, the PG pin will assert 10ms after the output is within its specified tolerance band. The PG delay period can be set independent of the soft-start ramp time via the I2C/SMBus interface.
6.3 Output Overvoltage Protection
The default response from an overvoltage fault is to immediately shut down. The device will continuously check for the presence of the fault condition, and when the fault condition no longer exists the device will be re-enabled. For continuous overvoltage protection when operating from an external clock, the only allowed response is an immediate shutdown. Please refer to Application Note AN13 for details on how to select specific overvoltage fault response options via I2C/SMBus.
6.4 Output Pre-Bias Protection
An output pre-bias condition exists when an externally applied voltage is present on a power supply's output before the power supply's control IC is enabled. Certain applications require that the converter not be allowed to sink current during start up if a pre-bias condition exists at the output. The ZL2105 provides pre-bias protection by sampling the output voltage prior to initiating an output ramp. If a pre-bias voltage lower than the target voltage exists after the pre-configured delay period has expired, the target voltage is set to match the existing pre-bias voltage and both drivers are enabled. The output voltage is then ramped to the final regulation value at the ramp rate set by the SS pin. The actual time the output will take to ramp from the pre-bias voltage to the target voltage will vary depending on the pre-bias voltage but the total time elapsed from when the delay period expires and when the output reaches its target value will match the pre-configured ramp time. See Figure 17.
The ZL2105 offers an internal output overvoltage protection circuit that can be used to protect sensitive load circuitry from being subjected to a voltage higher than its prescribed limits. A hardware comparator is used to compare the actual output voltage (seen at the VSEN pin) to a threshold set to 15% higher than the target output voltage (the default setting). If the VSEN voltage exceeds this threshold, the PG pin will deassert and the device can then respond in a number of ways as follows: 1. Initiate an immediate shutdown until the fault has been cleared. The user can select a specific number of retry attempts. 2. Turn off the high-side MOSFET and turn on the low-side MOSFET. The low-side MOSFET remains on until the device attempts a restart.
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current limit threshold has been selected (see Section 5.10 "Current Limit Threshold Selection"), the user may determine the desired course of action in response to the fault condition. The following overcurrent protection response options are available: 1. Initiate a shutdown and attempt to restart an infinite number of times with a preset delay period between attempts. 2. Initiate a shutdown and attempt to restart a preset number of times with a preset delay period between attempts. 3. Continue operating for a given delay period, followed by shutdown if the fault still exists. 4. Continue operating through the fault (this could result in permanent damage to the power supply). 5. Initiate an immediate shutdown. The default response from an overcurrent fault is an immediate shutdown of the device. The device will continuously check for the presence of the fault condition, and if the fault condition no longer exists the device will be re-enabled. Please refer to Application Note AN13 for details on how to select specific overcurrent fault response options via I2C/SMBus.
6.6 Thermal Overload Protection
Figure 17. Output Responses to Pre-bias Voltages
If a pre-bias voltage higher than the target voltage exists after the pre-configured delay period has expired, the target voltage is set to match the existing pre-bias voltage and both drivers are enabled with a PWM duty cycle that would ideally create the pre-bias voltage. Once the pre-configured soft-start ramp period has expired, the PG pin will be asserted (assuming the pre-bias voltage is not higher than the overvoltage limit). The PWM will then adjust its duty cycle to match the original target voltage and the output will ramp down to the pre-configured output voltage. If a pre-bias voltage higher than the overvoltage limit exists, the device will not initiate a turn-on sequence and will declare an overvoltage fault condition to exist. In this case, the device will respond based on the output overvoltage fault response method that has been selected. See Section 6.3 "Output Overvoltage Protection," for response options due to an overvoltage condition.
6.5 Output Overcurrent Protection
The ZL2105 includes an on-chip thermal sensor that continuously measures the internal temperature of the die and shuts down the device when the temperature exceeds the preset limit. The default temperature limit is set to 125C in the factory, but the user may set the limit to a different value if desired. The user may select one of the following overtemperature protection response options: 1. Initiate a shutdown and attempt to restart an infinite number of times with a preset delay period between attempts. 2. Initiate a shutdown and attempt to restart a preset number of times with a preset delay period between attempts. 3. Continue operating for a given delay period, followed by shutdown if the fault still exists.
The ZL2105 can protect the power supply from damage if the output is shorted to ground or if an overload condition is imposed on the output. Once the
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4. Continue operating through the fault (this could result in permanent damage to the power supply). 5. Initiate an immediate shutdown. If the user has configured the device to restart, the device will wait the preset delay period (if so chosen) and will then check the device temperature. If the temperature has dropped below a threshold that is approx 15C lower than the selected temperature fault limit, the device will attempt to re-start. If the temperature still exceeds the fault limit the device will wait the preset delay period and retry again. The default response from a temperature fault is an immediate shutdown of the device. The device will continuously check for the fault condition, and once the fault has cleared the ZL2105 will be re-enabled. Please refer to Application Note AN13 for details on how to select specific over-temperature fault response options via I2C/SMBus.
6.7 Voltage Tracking
VTRK
Numerous high performance systems place stringent demands on the order in which the power supply voltages are turned on. This is particularly true when powering FPGAs, ASICs, and other advanced processor devices that require multiple supply voltages to power a single die. In most cases, the I/O interface operates at a higher voltage than the core and therefore the core supply voltage must not exceed the I/O supply voltage according to the manufacturers' specifications. Voltage tracking protects these sensitive ICs by limiting the differential voltage between multiple power supplies during the power-up and power down sequence. The ZL2105 integrates a lossless tracking scheme that allows its output to track a voltage that is applied to the VTRK pin with no external components required. The VTRK pin is an analog input that, when tracking mode is enabled, configures the voltage applied to the VTRK pin to act as a reference for the device's output regulation.
Figure 18. Tracking Modes
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Table 22. Tracking Mode Configuration Tracking Upper Track Limit RSS Ratio 10 k Limited by target voltage 11 k 100% 12.1 k Limited by VTRK pin voltage 13.3 k 14.7 k 16.2 k 17.8 k 19.6 k 50% Limited by VTRK pin voltage Limited by target voltage
Ramp-up/ramp-down Behavior Output not allowed to decrease before PG Output will always follow VTRK Output not allowed to decrease before PG Output will always follow VTRK Output not allowed to decrease before PG Output will always follow VTRK Output not allowed to decrease before PG Output will always follow VTRK 6.8 Voltage Margining
The ZL2105 offers two mode of tracking as follows: 1. Coincident. This mode configures the ZL2105 to ramp its output voltage at the same rate as the voltage applied to the VTRK pin. 2. Ratiometric. This mode configures the ZL2105 to ramp its output voltage at a rate that is a percentage of the voltage applied to the VTRK pin. The default setting is 50%, but an external resistor string may be used to configure a different tracking ratio. Figure 18 illustrates the typical connection and the two tracking modes. The master ZL2105 device in a tracking group is defined as the device that has the highest target output voltage within the group. This master device will control the ramp rate of all tracking devices and is not configured for tracking mode. A delay of at least 10 ms must be configured into the master device using the DLY pin, and the user may also configure a specific ramp rate using the SS pin. Tracking mode is enabled through the CFG pin as shown in Table 25 on Page 30. Any device that is configured for tracking mode will ignore its soft-start delay and ramp time settings (SS and DLY pins) and its output will take on the turnon/turn-off characteristics of the reference voltage present at the VTRK pin. The tracking mode for all other devices can be set by connecting a resistor from the SS pin to ground according to Table 22. All of the ENABLE pins in the tracking group must be connected together and driven by a single logic source. Tracking mode can also be configured via the I2C/SMBus interface by using the TRACK_CONFIG PMBus command. Please refer to Application Note AN13 for more information on configuring tracking mode using PMBus.
The ZL2105 offers a simple means to vary its output higher or lower than its nominal voltage setting in order to determine whether the load device is capable of operating over its specified supply voltage range. The MGN pin is a TTL-compatible input that can be driven directly by a processor I/O pin or other logiclevel output. The ZL2105's output will be forced higher than its nominal set point when the MGN pin is driven HIGH, and the output will be forced lower than its nominal set point when the MGN pin is driven LOW. When the MGN pin is left floating (high impedance), the ZL2105's output voltage will be set to its nominal voltage set point determined by the V0 and V1 pins and/or the I2C/SMBus settings. Default margin limits of VNOM 5% are pre-loaded in the factory, but the margin limits can be modified through the I2C/SMBus interface to as high as VNOM + 10% or as low as 0V, where VNOM is the nominal output voltage set point determined by the V0 and V1 pins. A safety feature prevents the user from configuring the output voltage to exceed VNOM + 10% under any conditions. The margin limits and the MGN pin command can both be set individually through the I2C/SMBus interface. Additionally, the transition rate between the nominal output voltage and either margin limit can be configured through the I2C interface. Please refer to Application Note AN13 for detailed instructions on modifying the margining configurations.
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6.9 I2C/SMBus Communications Table 24. Additional SMBus Address Values SMBus SMBus RSA RSA Address Address 0x20 0x2D 10 k 34.8 k 0x21 0x2E 11 k 38.3 k 0x22 0x2F 12.1 k 42.2 k 0x23 0x30 13.3 k 46.4 k 0x24 0x31 14.7 k 51.1 k 0x25 0x32 16.2 k 56.2 k 0x26 0x33 17.8 k 61.9 k 0x27 0x34 19.6 k 68.1 k 0x28 0x35 21.5 k 75 k 0x29 0x36 23.7 k 82.5 k 0x2A 0x37 26.1 k 90.9 k 0x2B 0x38 28.7 k 100 k 0x2C 31.6 k 6.11 Phase Spreading
The ZL2105 provides an I C/SMBus digital interface that enables the user to configure all aspects of the device operation as well as monitor the input and output parameters. The ZL2105 can be used with any standard 2-wire I2C host device. In addition, the device is compatible with SMBus version 2.0 and includes an SALRT line to help mitigate bandwidth limitations related to continuous fault monitoring. Pull-up resistors are required on the I2C/SMBus. The ZL2105 accepts most standard PMBus commands.
6.10 I2C/SMBus Device Address Selection
2
When communicating with multiple PMBus devices using the I2C/SMBus interface, each device must have its own unique address so the host can distinguish between the devices. The device address can be set according to the pin-strap options listed in Table 23. Address values are right-justified.
Table 23. SMBus Device Address Selection SA Pin Setting SMBus Address LOW 0x20 OPEN 0x21 HIGH Reserved
If additional device addresses are required, a resistor can be connected to the SA pin according to Table 24 to provide up to 25 unique device addresses.
When multiple point of load converters share a common DC input supply, it is desirable to adjust the clock phase offset of each device such that not all devices start to switch simultaneously. Setting each converter to start its switching cycle at a different point in time can dramatically reduce input capacitance requirements and efficiency losses. Since the peak current drawn from the input supply is effectively spread out over a period of time, the peak current drawn at any given moment is reduced and the power losses proportional to the IRMS2 are reduced dramatically. In order to enable phase spreading, all converters must be synchronized to the same switching clock. The CFG pin is used to set the configuration of the SYNC pin for each device as described in Section 5.8 "Switching Frequency and PLL," on Page 17.
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Selecting the phase offset for the device is accomplished by selecting a device address according to the following equation: Phase offset = device address x 45 For example: * A device address of 0x00 or 0x20 would configure no phase offset * A device address of 0x01 or 0x21 would configure 45 of phase offset * A device address of 0x02 or 0x22 would configure 90 of phase offset The phase offset of each device may also be set to any value between 0 and 337.5 in 22.5 increments via the I2C/SMBus interface. Refer to Application Note AN13 for further details.
6.12 Output Sequencing
turn on each device in the address chain until all devices connected have been turned on. When turning off, the device with the highest address will turn off first followed in reverse order by the other devices in the group.
Table 25. CFG Pin Configurations for Sequencing and Tracking SYNC Pin Sequencing RCFG Config Configuration Input 10 k Sequencing and Tracking Auto detect 11 k are disabled Output 12.1 k Device is the first device Input 14.7 k in a nested sequencing Auto detect 16.2 k group. Turn-on order is based on device address. Output 17.8 k 21.5 k 23.7 k 26.1 k 31.6 k 34.8 k 38.3 k 42.2 k 46.4 k 51.1 k Input Auto detect Output Input Auto detect Output Input Auto detect Output Device is a last device in a nested sequencing group. Turn-on order is based on device address. Device is the middle device in a nested sequencing group. Turnon order is based on device address. Sequencing is Disabled. Voltage Tracking enabled as defined in Table 22.
A group of Zilker Labs devices (both ZL2005 and ZL2105) may be configured to power up in a predetermined sequence. This feature is especially useful when powering advanced processors, FPGAs, and ASICs that require one supply to reach its operating voltage prior to another supply reaching its operating voltage in order to avoid latch-up from occurring. Multi-device sequencing can be achieved by configuring each device through the I2C/SMBus interface or by using Zilker Labs patented autonomous sequencing mode. Autonomous sequencing mode configures sequencing by using events transmitted between devices over the I2C/SMBus pins SCL and SDA. No I2C or SMBus host device is involved in this method, but the SCL and SDA pins must be interconnected between all devices that the user wishes to sequence using this method. (note: pull-up resistors on SCL and SDA are required and should be selected using the criteria in the SMBus 2.0 specification). The sequencing order is determined using each device's I2C/SMBus device address. Using autonomous sequencing mode (configured using the CFG pin), the devices must exhibit sequential device addresses with no missing addresses in the chain. This mode will also constrain each device to have a phase offset according to its device address as described in Phase Spreading. The group will turn on in order starting with the device with the lowest address and will continue through to
Sequencing is configured by connecting a resistor from the CFG pin to ground as described in Table 25. The CFG pin is used to set the configuration of the SYNC pin as well as to determine the sequencing method and order. Refer to Section 5.8 "Switching Frequency and PLL," on Page 17 for more details on the operating parameters of the SYNC pin. Multiple device sequencing may also be achieved by issuing PMBus commands to assign the preceding device in the sequencing chain as well as the device that will follow in the sequencing chain. This method places fewer restrictions on device address (no need of sequential address) and also allows the user to assign any phase offset to any device irrespective of its device address. Note: Event based sequencing and fault spreading are broadcast in address groups of up to eight Zilker Labs Digital-DC devices. An address group consists of all devices whose addresses differ in only the three least significant bits of the address. For example, addresses
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0x20, 0x25 and 0x27 are all within the same group. Addresses 0x1F, 0x20 and 0x28 are all in different groups. Device in the same address group can broadcast power on and power down sequencing and fault spreading events with each other. Devices in different group cannot. The Enable pins of all devices in a sequencing group must be tied together and driven high to initiate a sequenced turn-on of the group. Enable must be driven low to initiate a sequenced turnoff of the group. Refer to Application Note AN13 for details on sequencing via the I2C/SMBus interface.
6.13 Monitoring via I C/SMBus
2
6.14 Temperature Monitoring using the XTEMP Pin
The ZL2105 supports measurement of an external device temperature using either a thermal diode integrated in a processor, FPGA or ASIC, or using a discrete diode-connected NPN transistor such as a 2N3904 or equivalent. Figure 19 illustrates the typical connections required.
XTEMP
ZL2105
SGND
100pF
2N3904
Discrete NPN
A system controller can monitor a wide variety of different ZL2105 system parameters through the I2C/SMBus interface. The device can monitor for fault conditions by monitoring the SALRT pin, which will be asserted when any number of pre-configured fault conditions occur. The device can also be monitored continuously for any number of power conversion parameters including but not limited to the following: * * * * * * * Input voltage Output voltage Output current Internal junction temperature Temperature of an external device Switching frequency Duty cycle
XTEMP
ZL2105
SGND
100pF
P FPGA DSP ASIC
Embedded Thermal Diode Figure 19. External Temperature Monitoring
Please refer to Application Note AN13 for details on how to monitor specific parameters via the I2C/SMBus interface.
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6.15 Non-Volatile Memory and Device Security Features
The ZL2105 has internal non-volatile memory where user configurations are stored. Integrated security measures ensure that the user can only restore the device to a level that has been made available to them. Refer to Section 5.6 "Start-up Procedure," for details on how the device loads stored values from internal memory during start-up. During the initialization process, the ZL2105 checks for stored values contained in its internal memory. The ZL2105 offers two internal memory storage units that are accessible by the user as follows: 1. Default Store: A power supply module manufacturer may want to protect the module from damage by preventing the user from being able to modify certain values that are related to the physical construction of the module. In this case, the module manufacturer would use the Default Store and would allow the user to restore the device to its default setting but would restrict the user from restoring the device to the factory settings. 2. User Store: The manufacturer of a piece of equipment may want to provide the ability to modify certain power supply settings while still protecting the equipment from modifying values that can lead to a system level fault. The equipment manufacturer would use the User Store to achieve this goal. Please refer to Application Note AN13 for details on how to set specific security measures via the I2C/SMBus interface.
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7. Package Dimensions
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8. Ordering Information
9. Related Documentation
The following application support documents and tools are available to help simplify your design.
Item Description
ZL2105EVK2 AN10 AN11 AN13 AN16
Evaluation Kit - 3A Integrated Digital DC-DC Converter Application Note: Digital-DC Thermal and Layout Guidelines Application Note: Digital-DC Component Selection Guide Application Note: PMBus Command Set Application Note: Digital-DC Control Loop Compensation
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10. Revision History
Rev. # Description Date
0.8 1.0 1.1
Preliminary Release Updated Table 1 and Table 3 to remove TBDs. Release to production. Added RFC to Fig. 3. Added charge pump cap value to Figs. 10 and 11. Added RVR to Figs. 8, 9, 10, and 12. Added SOA curve on Page 9. Added RVR description on Page 20. Changed max switching frequency from 2MHz to 1.2MHz Removed RFC from Fig. 3. Updated SOA curve on Page 9. Added ferrite bead to applications circuit on Page 8 Added 100pF cap to temp circuit on Page 30 Changed max switching frequency from 1.2MHz to 2MHz Updated SOA curves on Page 9. Updated Ordering Information on Page 34 Corrected OV response description on Page 25 Assigned file number FN6851 to datasheet as this will be the first release with an Intersil file number. Replaced header and footer with Intersil header and footer. Updated disclaimer information to read "Intersil and it's subsidiaries including Zilker Labs, Inc." No changes to datasheet content
July 2006 4/12/07 5/15/07
1.2
11/29/07
1.3 1.4
1/10/08 May 2008
FN6851.0
February 2009
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Zilker Labs, Inc. 4301 Westbank Drive Building A-100 Austin, TX 78746 Tel: 512-382-8300 Fax: 512-382-8329
(c) 2008, Zilker Labs, Inc. All rights reserved. Zilker Labs, Digital-DC, and the Zilker Labs Logo are trademarks of Zilker Labs, Inc. All other products or brand names mentioned herein are trademarks of their respective holders. This document contains information on a product under development. Specifications are subject to change without notice. Pricing, specifications and availability are subject to change without notice. Please see www.zilkerlabs.com for updated information. This product is not intended for use in connection with any high-risk activity, including without limitation, air travel, life critical medical operations, nuclear facilities or equipment, or the like. The reference designs contained in this document are for reference and example purposes only. THE REFERENCE DESIGNS ARE PROVIDED "AS IS" AND "WITH ALL FAULTS" AND INTERSIL CORPORATION AND IT'S SUBSIDIARIES INCLUDING ZILKER LABS, INC. DISCLAIMS ALL WARRANTIES, WHETHER EXPRESS OR IMPLIED. ZILKER LABS SHALL NOT BE LIABLE FOR ANY DAMAGES, WHETHER DIRECT, INDIRECT, CONSEQUENTIAL (INCLUDING LOSS OF PROFITS), OR OTHERWISE, RESULTING FROM THE REFERENCE DESIGNS OR ANY USE THEREOF. Any use of such reference designs is at your own risk and you agree to indemnify Intersil Corporation and it's subsidiaries including Zilker Labs, Inc. for any damages resulting from such use.
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