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HIP6018
Data Sheet April 1998 File Number
4497.1
Advanced PWM and Dual Linear Power Control
The HIP6018 provides the power control and protection for three output voltages in high-performance microprocessor and computer applications. The IC integrates a PWM controllers, a linear regulator and a linear controller as well as the monitoring and protection functions into a single package. The PWM controller regulates the microprocessor core voltage with a synchronous-rectified buck converter. The linear controller regulates power for the GTL bus and the linear regulator provides power for the clock driver circuit. The HIP6018 includes an Intel-compatible, TTL 5-input digital-to-analog converter (DAC) that adjusts the core PWM output voltage from 2.1VDC to 3.5VDC in 0.1V increments and from 1.8VDC to 2.05VDC in 0.05V steps. The precision reference and voltage-mode control provide 1% static regulation. The linear regulator uses an internal pass device to provide 2.5V2.5%. The linear controller drives an external N-channel MOSFET to provide 1.5V2.5%. The HIP6018 monitors all the output voltages. A single Power Good signal is issued when the core is within 10% of the DAC setting and the other levels are above their undervoltage levels. Additional built-in over-voltage protection for the core output uses the lower MOSFET to prevent output voltages above 115% of the DAC setting. The PWM overcurrent function monitors the output current by using the voltage drop across the upper MOSFET's rDS(ON), eliminating the need for a current sensing resistor.
Features
* Provides 3 Regulated Voltages - Microprocessor Core, Clock and GTL Power * Drives N-Channel MOSFETs * Operates from +3.3V, +5V and +12V Inputs * Simple Single-Loop PWM Control Design - Voltage-Mode Control * Fast Transient Response - High-Bandwidth Error Amplifier - Full 0% to 100% Duty Ratios * Excellent Output Voltage Regulation - Core PWM Output: 1% Over Temperature - Other Outputs: 2.5% Over Temperature * TTL-compatible 5-Bit Digital-to-Analog Core Output Voltage Selection - Wide Range . . . . . . . . . . . . . . . . . . . 1.8VDC to 3.5VDC - 0.1V Steps . . . . . . . . . . . . . . . . . . . . 2.1VDC to 3.5VDC - 0.05V Steps . . . . . . . . . . . . . . . . . . 1.8VDC to 2.05VDC * Power-Good Output Voltage Monitor * Microprocessor Core Voltage Protection Against Shorted MOSFET * Over-Voltage and Over-Current Fault Monitors - Does Not Require Extra Current Sensing Element, Uses MOSFET's rDS(ON) * Small Converter Size - Constant Frequency Operation - 200kHz Free-Running Oscillator; Programmable from 50kHz to over 1MHz
Ordering Information
PART NUMBER HIP6018CB HIP6018EVAL1 TEMP. RANGE (oC) 0 to 70 Evaluation Board PACKAGE 24 Ld SOIC PKG. NO. M24.3
Applications
* Full Motherboard Power Regulation for Computers * Low-Voltage Distributed Power Supplies
Pinout
HIP6018 (SOIC) TOP VIEW
VCC 1 VID4 2 VID3 3 VID2 4 VID1 5 VID0 6 PGOOD 7 FAULT 8 SS 9 RT 10 FB2 11 VIN2 12 24 UGATE1 23 PHASE1 22 LGATE1 21 PGND 20 OCSET1 19 VSEN1 18 FB1 17 COMP1 16 FB3 15 DRIVE3 14 GND 13 VOUT2
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CAUTION: These devices are sensitive to electrostatic discharge; follow proper IC Handling Procedures. http://www.intersil.com or 407-727-9207 | Copyright (c) Intersil Corporation 1999
Block Diagram
VSEN1 VCC
OCSET1
FB3
+
-
2-225
+ +
DRIVE3
200mA RESET (POR) +
0.3V
LINEAR UNDERVOLTAGE 110% POWER-ON 3V
3V INHIBIT + + 90% +
-
VIN2
PGOOD
+
VOUT2
+
0.23A OC2 LUV +
115%
-
1.26V
FB2
OV SOFTSTART AND FAULT LOGIC OC1 +
UPPER DRIVE
VCC UGATE1
HIP6018
FIGURE 1.
FAULT
-
PHASE1 INHIBIT
+ VCC DACOUT 11A
-
+
GATE CONTROL
ERROR AMP
PWM PWM COMP LOWER DRIVE
VCC LGATE1 PGND GND OSCILLATOR
4V
TTL D/A CONVERTER (DAC)
SS
VID4 VID0 VID2 VID1 VID3
FB1
COMP1
RT
HIP6018 Simplified Power System Diagram
+5VIN +3.3VIN VOUT2 Q1 LINEAR REGULATOR PWM1 CONTROLLER VOUT1 Q2
HIP6018
Q3 VOUT3 LINEAR CONTROLLER
FIGURE 2.
Typical Application
+12VIN +5VIN CIN VCC OCSET1 PGOOD VOUT2 2.5V COUT2 VOUT2 FB2 UGATE1 PHASE1 Q1 LOUT1 VOUT1 1.8V TO 3.5V POWERGOOD
+3.3VIN
VIN2
LGATE1 Q3 VOUT3 1.5V COUT3 VID0 VID1 VID2 VID3 VID4 GND FAULT RT SS CSS FB1 COMP1 DRIVE3 PGND
Q2 CR1 COUT1
HIP6018
FB3 VSEN1
FIGURE 3.
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HIP6018
Absolute Maximum Ratings
Supply Voltage, VCC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . +15V PGOOD, RT, FAULT, and GATE Voltage .GND - 0.3V to VCC + 0.3V Input, Output or I/O Voltage . . . . . . . . . . . . . . . . . . GND -0.3V to 7V
Thermal Information
Thermal Resistance (Typical, Note 1) JA (oC/W) SOIC Package. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75 SOIC Package (with 3 in2 of copper) . . . . . . . . . . . 65 Maximum Junction Temperature (Plastic Package) . . . . . . . .150oC Maximum Storage Temperature Range . . . . . . . . . . -65oC to 150oC Maximum Lead Temperature (Soldering 10s) . . . . . . . . . . . . .300oC (SOIC - Lead Tips Only)
Operating Conditions
Supply Voltage, VCC . . . . . . . . . . . . . . . . . . . . . . . . . . . +12V 10% Ambient Temperature Range . . . . . . . . . . . . . . . . . . . . . 0oC to 70oC Junction Temperature Range . . . . . . . . . . . . . . . . . . . . 0oC to 125oC
CAUTION: Stresses above those listed in "Absolute Maximum Ratings" may cause permanent damage to the device. This is a stress only rating and operation of the device at these or any other conditions above those indicated in the operational sections of this specification is not implied.
NOTE: 1. JA is measured with the component mounted on an evaluation PC board in free air.
Electrical Specifications
PARAMETER VCC SUPPLY CURRENT Nominal Supply POWER-ON RESET Rising VCC Threshold Falling VCC Threshold
Recommended Operating Conditions, Unless Otherwise Noted. Refer to Figures 1, 2 and 3 SYMBOL TEST CONDITIONS MIN TYP MAX UNITS
ICC
UGATE1, DRIVE3, LGATE1, and VOUT2 Open
-
10
-
mA
VOCSET = 4.5V VOCSET = 4.5V
8.6 8.2 2.45 -
2.55 500 1.25
10.4 10.2 2.65 -
V V V mV V
Rising VIN2 Under-Voltage Threshold VIN2 Under-Voltage Hysteresis Rising VOCSET1 Threshold OSCILLATOR Free Running Frequency Total Variation Ramp Amplitude REFERENCE and DAC DAC(VID0-VID4) Input Low Voltage DAC(VID0-VID4) Input High Voltage DACOUT Voltage Accuracy Reference Voltage (Pin FB2 and FB3) LINEAR REGULATOR Regulation Under-Voltage Level Under-Voltage Hysteresis Over-Current Protection Over-current Protection During Start-Up LINEAR CONTROLLER Regulation Under-Voltage Level FB3UV VSEN3 = DRIVE3, 0 < IDRIVE3 < 20mA FB3 Rising FB2UV 10mA < IVOUT2 < 150mA FB2 Rising VOSC RT = OPEN 6k < RT to GND < 200k RT = Open
185 -15 -
200 1.9
215 +15 -
kHz % VP-P
2.0 -1.0 1.240
1.265
0.8 +1.0 1.290
V V % V
-2.5 180 560
75 6 230 700
2.5 87 -
% % % mA mA
-2.5 -
75
2.5 87
% %
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HIP6018
Electrical Specifications
PARAMETER Under-Voltage Hysteresis DRIVE3 Source Current PWM CONTROLLER ERROR AMPLIFIER DC Gain Gain-Bandwidth Product Slew Rate PWM CONTROLLER GATE DRIVER Upper Drive Source Upper Drive Sink Lower Drive Source Lower Drive Sink PROTECTION VOUT1 Over-Voltage Trip FAULT Sourcing Current OCSET1 Current Source Soft-Start Current Chip Shutdown Soft-Start Threshold POWER GOOD VOUT1 Upper Threshold VOUT1 Under Voltage VOUT1 Hysteresis (VSEN1 / DACOUT) PGOOD Voltage Low VPGOOD VSEN1 Rising VSEN1 Rising Upper/Lower Threshold IPGOOD = -4mA 108 92 2 110 94 0.5 % % % V IOVP IOCSET ISS VSEN1 Rising VFAULT = 10V VOCSET = 4.5VDC 112 10 170 115 14 200 11 118 230 1.0 % mA A A V IUGATE RUGATE ILGATE RLGATE VCC = 12V, VUGATE1 (or VGATE2) = 6V VUGATE1-PHASE1 = 1V VCC = 12V, VLGATE1 = 1V VLGATE1 = 1V 1 1.7 1 1.4 3.5 3.0 A A GBWP SR COMP = 10pF 88 15 6 dB MHz V/s VIN2 - DRIVE3 > 0.6V Recommended Operating Conditions, Unless Otherwise Noted. Refer to Figures 1, 2 and 3 (Continued) SYMBOL TEST CONDITIONS MIN 20 TYP 6 40 MAX UNITS % mA
Typical Performance Curves
100 CUGATE1 = CLGATE1 = CGATE VVCC = 12V, VIN = 5V 1000 RESISTANCE (k) 80 RT PULLUP TO +12V ICC (mA) 60 CGATE = 3600pF 40 CGATE = 1500pF RT PULLDOWN TO VSS 20 CGATE = 660pF 0 100 CGATE = 4800pF
100
10
10
100 SWITCHING FREQUENCY (kHz)
1000
200
300
400
500
600
700
800
900
1000
SWITCHING FREQUENCY (kHz)
FIGURE 4. RT RESISTANCE vs FREQUENCY
FIGURE 5. BIAS SUPPLY CURRENT vs FREQUENCY
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HIP6018 Functional Pin Description
VSEN1 (Pin 19)
This pin is connected to the PWM converter's output voltage. The PGOOD and OVP comparator circuits use this signal to report output voltage status and for over voltage protection.
PHASE1 (Pin 23)
Connect the PHASE pin to the PWM converter's upper MOSFET source. This pin is used to monitor the voltage drop across the upper MOSFET for over-current protection.
UGATE1 (Pin 24)
Connect UGATE pin to the PWM converter's upper MOSFET gate. This pin provides the gate drive for the upper MOSFET.
OCSET1 (Pin 20)
Connect a resistor (ROCSET) from this pin to the drain of the upper MOSFET. ROCSET, an internal 200A current source (IOCSET), and the upper MOSFET on-resistance (rDS(ON)) set the PWM converter over-current (OC) trip point according to the following equation:
I OCSET x R OCSET I PEAK = --------------------------------------------------r DS ( ON )
PGND (Pin 21)
This is the power ground connection. Tie the PWM converter's lower MOSFET source to this pin.
LGATE1 (Pin 22)
Connect LGATE1 to the PWM converter's lower MOSFET gate. This pin provides the gate drive for the lower MOSFET.
An over-current trip cycles the soft-start function. Sustaining an over-current for 2 soft-start intervals shuts down the controller.
VCC (Pin 1)
Provide a 12V bias supply for the IC to this pin. This pin also provides the gate bias charge for all the MOSFETs controlled by the IC.
SS (Pin 9)
Connect a capacitor from this pin to ground. This capacitor, along with an internal 11A (typically) current source, sets the soft-start interval of the converter. Pulling this pin low with an open drain signal will shut down the IC.
RT (Pin 10)
This pin provides oscillator switching frequency adjustment. By placing a resistor (RT) from this pin to GND, the nominal 200kHz switching frequency is increased according to the following equation:
5 x 10 Fs 200kHz + -------------------R T ( k )
6
VID0, VID1, VID2, VID3, VID4 (Pins 6, 5, 4, 3 and 2)
VID0-4 are the input pins to the 5-bit DAC. The states of these five pins program the internal voltage reference (DACOUT). The level of DACOUT sets the core converter output voltage. It also sets the core PGOOD and OVP thresholds.
(RT to GND)
Conversely, connecting a pull-up resistor (RT) from this pin to VCC reduces the switching frequency according to the following equation:
4 x 10 Fs 200kHz - -------------------R T ( k )
7
COMP1 and FB1 (Pins 17 and 18)
COMP1 and FB1 are the available external pins of the PWM error amplifier. The FB1 pin is the inverting input of the error amplifier. Similarly, the COMP1 pin is the error amplifier output. These pins are used to compensate the voltagecontrol feedback loop of the PWM converter.
(RT to 12V)
FAULT (Pin 8)
This pin is low during normal operation, but it is pulled to VCC in the event of an over-voltage or over-current condition.
GND (Pin 14)
Signal ground for the IC. All voltage levels are measured with respect to this pin.
DRIVE3 (Pin 15)
Connect this pin to the gate of an external MOSFET. This pin provides the drive for the linear controller's pass transistor.
PGOOD (Pin 7)
PGOOD is an open collector output used to indicate the status of the output voltages. This pin is pulled low when the core output is not within 10% of the DACOUT reference voltage and the other outputs are below their under-voltage thresholds. The PGOOD output is open for VID codes that inhibit operation. See Table 1.
FB3 (Pin 16)
Connect this pin to a resistor divider to set the linear controller output voltage.
VOUT2 (Pin 13)
Output of the linear regulator. Supplies current up to 230mA.
FB2 (Pin 11)
Connect this pin to a resistor divider to set the linear regulator output voltage.
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HIP6018
VIN2 (Pin 12)
This pin supplies power to the internal regulator. Connect this pin to a suitable 3.3V source. Additionally, this pin is used to monitor the 3.3V supply. If, following a startup cycle, the voltage drops below 2.05V (typically), the chip shuts down. A new soft-start cycle is initiated upon return of the 3.3V supply above the undervoltage threshold. Figure 3 shows the soft-start sequence for the typical application. At T0 the SS voltage rapidly increases to approximately 1V. At T1, the SS pin and error amplifier output voltage reach the valley of the oscillator's triangle wave. The oscillator's triangular waveform is compared to the clamped error amplifier output voltage. As the SS pin voltage increases, the pulse-width on the PHASE pin increases. The interval of increasing pulse-width continues until each output reaches sufficient voltage to transfer control to the input reference clamp. If we consider the 2.0V output (VOUT1) in Figure 3, this time occurs at T2. During the interval between T2 and T3, the error amplifier reference ramps to the final value and the converter regulates the output to a voltage proportional to the SS pin voltage. At T3 the input clamp voltage exceeds the reference voltage and the output voltage is in regulation.
Description
Operation
The HIP6018 monitors and precisely controls 4 output voltage levels (Refer to Figures 1, 2, and 3). It is designed for microprocessor computer applications with 3.3V and 5V power, and 12V bias input from an ATX power supply. The IC has one PWM controller, a linear controller, and a linear regulator. The PWM controller is designed to regulate the microprocessor core voltage (VOUT1) by driving 2 MOSFETs (Q1 and Q2) in a synchronous-rectified buck converter configuration. The core voltage is regulated to a level programmed by the 5-bit digital-to-analog converter (DAC). An integrated linear regulator supplies the 2.5V clock power (VOUT2). The linear controller drives an external MOSFET (Q3) to supply the GTL bus power (VOUT3).
PGOOD (2V/DIV) 0V SOFT-START (1V/DIV)
Initialization
The HIP6018 automatically initializes upon receipt of input power. Special sequencing of the input supplies is not necessary. The Power-On Reset (POR) function continually monitors the input supply voltages. The POR monitors the bias voltage (+12VIN) at the VCC pin, the 5V input voltage (+5VIN) on the OCSET1 pin, and the 3.3V input on the VIN2 pin. The normal level on OCSET1 is equal to +5VIN less a fixed voltage drop (see over-current protection). The POR function initiates soft-start operation after all three input supply voltages exceed their POR thresholds.
0V
VOUT2 ( = 2.5V) VOUT1 (DAC = 2V) OUTPUT VOLTAGES (0.5V/DIV) VOUT3 ( = 1.5V)
0V T0 T1 T2 T3 TIME T4
Soft-Start
The POR function initiates the soft-start sequence. Initially, the voltage on the SS pin rapidly increases to approximately 1V (this minimizes the soft-start interval). Then an internal 11A current source charges an external capacitor (CSS) on the SS pin to 4V. The PWM error amplifier reference input (+ terminal) and output (COMP1 pin) is clamped to a level proportional to the SS pin voltage. As the SS pin voltage slews from 1V to 4V, the output clamp generates PHASE pulses of increasing width that charge the output capacitor(s). After this initial stage, the reference input clamp slows the output voltage rate-of-rise and provides a smooth transition to the final set voltage. Additionally both linear regulator's reference inputs are clamped to a voltage proportional to the SS pin voltage. This method provides a rapid and controlled output voltage rise.
FIGURE 6. SOFT-START INTERVAL
The remaining outputs are also programmed to follow the SS pin voltage. Each linear output (VOUT2 and VOUT3) initially follows a ramp similar to that of the PWM output. When each output reaches sufficient voltage the input reference clamp slows the rate of output voltage rise. The PGOOD signal toggles `high' when all output voltage levels have exceeded their under-voltage levels. See the Soft-Start Interval section under Applications Guidelines for a procedure to determine the soft-start interval.
Fault Protection
All three outputs are monitored and protected against extreme overload. A sustained overload on any linear
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HIP6018
regulator output or an over-voltage on the PWM output disables all converters and drives the FAULT pin to VCC.
LUV OVER CURRENT LATCH OC1 SQ R 0.15V + S COUNTER R SS 4V + UP POR OV FAULT LATCH SQ R FAULT VCC INHIBIT
-
FIGURE 7. FAULT LOGIC - SIMPLIFIED SCHEMATIC
Figures 8 and 9 illustrate the over-current protection with an overload on OUT1. The overload is applied at T0 and the current increases through the output inductor (LOUT1). At time T1, the OVER-CURRENT1 comparator trips when the voltage across Q1 (ID * rDS(ON)) exceeds the level programmed by ROCSET. This inhibits all outputs, discharges the soft-start capacitor (CSS) with a 11A current sink, and increments the counter. CSS recharges at T2 and initiates a soft-start cycle with the error amplifiers clamped by soft-start. With OUT1 still overloaded, the inductor current increases to trip the overcurrent comparator. Again, this inhibits all outputs, but the soft-start voltage continues increasing to 4V before discharging. The counter increments to 2. The soft-start cycle repeats at T3 and trips the over-current comparator. The SS pin voltage increases to 4V at T4 and the counter increments to 3. This sets the fault latch to disable the converter. The fault is reported on the FAULT pin.
FAULT/RT
INDUCTOR CURRENTSOFT-START
Figure 7 shows a simplified schematic of the fault logic. An over-voltage detected on VSEN1 immediately sets the fault latch. A sequence of three over-current fault signals also sets the fault latch. A comparator indicates when CSS is fully charged (UP signal), such that an under-voltage event on either linear output (FB2 or FB3) is ignored until after the soft-start interval (T4 in Figure 6). At startup, this allows VOUT2 and VOUT3 to slew up over increased time intervals, without generating a fault. Cycling the bias input voltage (+12VIN on the VCC pin) off then on resets the counter and the fault latch.
10V 0V COUNT =1 4V 2V 0V OVERLOAD APPLIED
FAULT REPORTED
COUNT =2
COUNT =3
Over-Voltage Protection
During operation, a short on the upper PWM MOSFET (Q1) causes VOUT1 to increase. When the output exceeds the over-voltage threshold of 115% (typical) of DACOUT, the over-voltage comparator trips to set the fault latch and turns Q2 on as required in order to regulate VOUT1 to 1.15 x DACOUT. This blows the input fuse and reduces VOUT1. The fault latch raises the FAULT pin close to VCC potential. A separate over-voltage circuit provides protection during the initial application of power. For voltages on the VCC pin below the power-on reset (and above ~4V), VOUT1 is monitored for voltages exceeding 1.26V. Should VSEN1 exceed this level, the lower MOSFET (Q2) is driven on as needed to regulate VOUT1 to 1.26V.
0A T0 T1 T2 TIME T3 T4
FIGURE 8. OVER-CURRENT OPERATION
Over-Current Protection
All outputs are protected against excessive over-currents. The PWM controller uses the upper MOSFET's onresistance, rDS(ON) to monitor the current for protection against shorted outputs. The linear regulator monitors the current of the integrated power device and signals an overcurrent condition for currents in excess of 230mA. Additionally, both the linear regulator and the linear controller monitor FB2 and FB3 for under-voltage to protect against excessive currents.
The linear regulator operates in the same way as PWM1 to over-current faults. Additionally, the linear regulator and linear controller monitor the feedback pins for an undervoltage. Should excessive currents cause FB2 or FB3 to fall below the linear under-voltage threshold, the LUV signal sets the over-current latch if CSS is fully charged. Blanking the LUV signal during the CSS charge interval allows the linear outputs to build above the under-voltage threshold during normal start-up. Cycling the bias input power off then on resets the counter and the fault latch. Resistor ROCSET1 programs the over-current trip level for the PWM converter. As shown in Figure 9, the internal 200A current sink develops a voltage across ROCSET (VSET) that is referenced to VIN. The DRIVE signal enables the over-current comparator (OVER-CURRENT1). When the voltage across the upper MOSFET (VDS(ON)) exceeds VSET, the over-current comparator trips to set the over-current latch. Both VSET and VDS are referenced to VIN and a small capacitor across ROCSET helps VOCSET track the variations of VIN due to
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HIP6018
MOSFET switching. The over-current function will trip at a peak inductor current (IPEAK) determined by:
I OCSET x R OCSET I PEAK = ---------------------------------------------------r DS ( ON )
OVER-CURRENT TRIP: VDS > VSET (iD * rDS(ON) > IOCSET * ROCSET) OCSET IOCSET 200A VCC + DRIVE OC1 + UGATE PHASE VCC GATE CONTROL LGATE PGND VPHASE = VIN - VDS VOCSET = VIN - VSET VDS ROCSET VIN = +5V
TABLE 1. VOUT1 VOLTAGE PROGRAM PIN NAME NOMINAL OUT1 VOLTAGE DACOUT INHIBIT INHIBIT 1.80 1.85 1.90 1.95 2.00 2.05 INHIBIT 2.1 2.2 2.3 2.4 2.5 2.6 2.7 2.8 2.9 3.0 3.1 3.2 3.3 3.4 3.5
VID4 0 0 0
VSET + ID
VID3 1 0 0 0 0 0 0 0 1 1 1 1 1 1 1 1 0 0 0 0 0 0 0 0
VID2 X 1 1 1 0 0 0 0 1 1 1 1 0 0 0 0 1 1 1 1 0 0 0 0
VID1 X 1 0 0 1 1 0 0 1 1 0 0 1 1 0 0 1 1 0 0 1 1 0 0
VID0 X X 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0
0 0 0 0 0 1 1
OVERCURRENT1 PWM HIP6018
-
FIGURE 9. OVER-CURRENT DETECTION
1 1
The OC trip point varies with MOSFET's temperature. To avoid over-current tripping in the normal operating load range, determine the ROCSET resistor from the equation above with: 1. The maximum rDS(ON) at the highest junction temperature. 2. The minimum IOCSET from the specification table. 3. Determine IPEAK for IPEAK > IOUT(MAX) + (I)/2, where I is the output inductor ripple current. For an equation for the output inductor ripple current see the section under component guidelines titled `Output Inductor Selection'.
1 1 1 1 1 1 1 1 1 1 1 1
OUT1 Voltage Program
The output voltage of the PWM converter is programmed to discrete levels between 1.8VDC and 3.5VDC . This output is designed to supply the microprocessor core voltage. The voltage identification (VID) pins program an internal voltage reference (DACOUT) through a TTL-compatible 5-bit digital-to-analog converter. The level of DACOUT also sets the PGOOD and OVP thresholds. Table 1 specifies the DACOUT voltage for the different combinations of connections on the VID pins. The VID pins can be left open for a logic 1 input, because they are internally pulled up to +5V by a 10A (typically) current source. Changing the VID inputs during operation is not recommended. The sudden change in the resulting reference voltage could toggle the PGOOD signal and exercise the over-voltage protection. All VID pin combinations resulting in an INHIBIT disable the IC and the open-collector at the PGOOD pin.
NOTE: 0 = connected to GND or VSS, 1 = open or connected to 5V through pull-up resistors, X = don't care
Application Guidelines
Soft-Start Interval
Initially, the soft-start function clamps the error amplifier's output of the PWM converter. After the output voltage increases to approximately 80% of the set value, the reference input of the error amplifier is clamped to a voltage proportional to the SS pin voltage. Both linear outputs follow a similar start-up sequence. The resulting output voltage sequence is shown in Figure 6.
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HIP6018
The soft-start function controls the output voltage rate of rise to limit the current surge at start-up. The soft-start interval is programmed by the soft-start capacitor, CSS. Programming a faster soft-start interval increases the peak surge current. The peak surge current occurs during the initial output voltage rise to 80% of the set value.
+5VIN +3.3VIN +12V CVCC
VCC GND VIN2 OCSET1
CIN
COCSET1 ROCSET1 Q1 LOUT1 VOUT1 LOAD
Shutdown
The PWM output does not switch until the soft-start voltage (VSS) exceeds the oscillator's valley voltage. Additionally, the reference on each linear's amplifier is clamped to the softstart voltage. Holding the SS pin low with an open drain or collector signal turns off all three regulators. The VID codes resulting in an INHIBIT as shown in Table 1 also shuts down the IC.
VOUT3 LOAD
Q3
GATE3 UGATE1 PHASE1 HIP6018 VOUT2 LGATE1 SS PGND
Q2
COUT1 CR1
VOUT2 LOAD COUT2
CSS
KEY ISLAND ON POWER PLANE LAYER ISLAND ON CIRCUIT PLANE LAYER VIA CONNECTION TO GROUND PLANE
Layout Considerations
MOSFETs switch very fast and efficiently. The speed with which the current transitions from one device to another causes voltage spikes across the interconnecting impedances and parasitic circuit elements. The voltage spikes can degrade efficiency, radiate noise into the circuit, and lead to device over-voltage stress. Careful component layout and printed circuit design minimizes the voltage spikes in the converter. Consider, as an example, the turn-off transition of the upper PWM MOSFET. Prior to turn-off, the upper MOSFET was carrying the full load current. During the turn-off, current stops flowing in the upper MOSFET and is picked up by the lower MOSFET (and/or parallel Schottky diode). Any inductance in the switched current path generates a large voltage spike during the switching interval. Careful component selection, tight layout of the critical components, and short, wide circuit traces minimize the magnitude of voltage spikes. Contact Intersil for evaluation board drawings of the component placement and printed circuit board. There are two sets of critical components in a DC-DC converter using a HIP6018 controller. The power components are the most critical because they switch large amounts of energy. The critical small signal components connect to sensitive nodes or supply critical bypassing current. The power components should be placed first. Locate the input capacitors close to the power switches. Minimize the length of the connections between the input capacitors and the power switches. Locate the output inductor and output capacitors between the MOSFETs and the load. Locate the PWM controller close to the MOSFETs. The critical small signal components include the bypass capacitor for VCC and the soft-start capacitor, CSS . Locate these components close to their connecting pins on the control IC. Minimize any leakage current paths from SS node because the internal current source is only 11A.
FIGURE 10. PRINTED CIRCUIT BOARD POWER PLANES AND ISLANDS
A multi-layer printed circuit board is recommended. Figure 10 shows the connections of the critical components in the converter. Note that capacitors CIN and COUT could each represent numerous physical capacitors. Dedicate one solid layer for a ground plane and make all critical component ground connections with vias to this layer. Dedicate another solid layer as a power plane and break this plane into smaller islands of common voltage levels. The power plane should support the input power and output power nodes. Use copper filled polygons on the top and bottom circuit layers for the phase nodes. Use the remaining printed circuit layers for small signal wiring. The wiring traces from the control IC to the MOSFET gate and source should be sized to carry 1A currents. The traces for OUT2 need only be sized for 0.2A. Locate COUT2 close to the HIP6018 IC.
PWM Controller Feedback Compensation
Both PWM controllers use voltage-mode control for output regulation. This section highlights the design consideration for a voltage-mode controller. Apply the methods and considerations to both PWM controllers. Figure 11 highlights the voltage-mode control loop for a synchronous-rectified buck converter. The output voltage is regulated to the reference voltage level. The reference voltage level is the DAC output voltage for the PWM controller. The error amplifier output (VE/A) is compared with the oscillator (OSC) triangular wave to provide a pulse-width modulated wave with an amplitude of VIN at the PHASE node. The PWM wave is smoothed by the output filter (LO and CO). The modulator transfer function is the small-signal transfer function of VOUT/VE/A. This function is dominated by a DC gain and the output filter, with a double pole break frequency at FLC and a zero at FESR. The DC gain of the modulator is simply the input voltage, VIN, divided by the peak-to-peak oscillator voltage, VOSC .
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HIP6018
VIN OSC PWM COMP DRIVER LO DRIVER PHASE CO ESR (PARASITIC) ZFB VE/A VOUT
Compensation Break Frequency Equations
1 F Z1 = ----------------------------------2 x R 2 x C1 1 F P1 = -----------------------------------------------------C1 x C2 2 x R 2 x --------------------- C1 + C2 1 F P2 = ----------------------------------2 x R 3 x C3
VOSC
+
1 F Z2 = -----------------------------------------------------2 x ( R1 + R3 ) x C3
ERROR AMP +
ZIN REFERENCE
DETAILED FEEDBACK COMPENSATION ZFB C2 C1 R2 C3 R1 COMP ZIN R3 VOUT
Figure 12 shows an asymptotic plot of the DC-DC converter's gain vs. frequency. The actual modulator gain has a peak due to the high Q factor of the output filter at FLC, which is not shown in Figure 12. Using the above guidelines should yield a compensation gain similar to the curve plotted. The open loop error amplifier gain bounds the compensation gain. Check the compensation gain at FP2 with the capabilities of the error amplifier. The closed loop gain is constructed on the log-log graph of Figure 12 by adding the modulator gain (in dB) to the compensation gain (in dB). This is equivalent to multiplying the modulator transfer function to the compensation transfer function and plotting the gain.
100 80 60 GAIN (dB) OPEN LOOP ERROR AMP GAIN 20LOG (R2/R1) MODULATOR GAIN
+
FB
FZ1 FZ2
FP1
FP2
HIP6018
REFERENCE
FIGURE 11. VOLTAGE-MODE BUCK CONVERTER COMPENSATION DESIGN
40 20 0 -20 -40
Modulator Break Frequency Equations
1 F LC = --------------------------------------2 x L O x C O 1 F ESR = ---------------------------------------2 x ESR x C O
20LOG (VIN/VOSC) COMPENSATION GAIN CLOSED LOOP GAIN FLC FESR 10K 100K 1M 10M
The compensation network consists of the error amplifier internal to the HIP6018 and the impedance networks ZIN and ZFB. The goal of the compensation network is to provide a closed loop transfer function with an acceptable 0dB crossing frequency (f0dB) and adequate phase margin. Phase margin is the difference between the closed loop phase at f0dB and 180 degrees. The equations below relate the compensation network's poles, zeros and gain to the components (R1, R2, R3, C1, C2, and C3) in Figure 11. Use these guidelines for locating the poles and zeros of the compensation network: 1. Pick Gain (R2/R1) for desired converter bandwidth 2. Place 1ST Zero Below Filter's Double Pole (~75% FLC) 3. Place 2ND Zero at Filter's Double Pole 4. Place 1ST Pole at the ESR Zero 5. Place 2ND Pole at Half the Switching Frequency 6. Check Gain against Error Amplifier's Open-Loop Gain 7. Estimate Phase Margin - Repeat if Necessary
-60
10
100
1K
FREQUENCY (Hz)
FIGURE 12. ASYMPTOTIC BODE PLOT OF CONVERTER GAIN
The compensation gain uses external impedance networks ZFB and ZIN to provide a stable, high bandwidth loop. A stable control loop has a 0dB gain crossing with -20dB/decade slope and a phase margin greater than 45 degrees. Include worst case component variations when determining phase margin.
Component Selection Guidelines
Output Capacitor Selection
The output capacitors for each output have unique requirements. In general the output capacitors should be selected to meet the dynamic regulation requirements. Additionally, the PWM converters require an output capacitor to filter the current ripple. The linear regulator is internally compensated and requires an output capacitor that meets the stability requirements. The load transient for the
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HIP6018
microprocessor core requires high quality capacitors to supply the high slew rate (di/dt) current demands.
0.7 0.6
PWM Output Capacitors
Modern microprocessors produce transient load rates above 10A/ns. High frequency capacitors initially supply the transient and slow the current load rate seen by the bulk capacitors. The bulk filter capacitor values are generally determined by the ESR (effective series resistance) and ESL (effective series inductance) parameters rather than actual capacitance. High frequency decoupling capacitors should be placed as close to the power pins of the load as physically possible. Be careful not to add inductance in the circuit board wiring that could cancel the usefulness of these low inductance components. Consult with the manufacturer of the load on specific decoupling requirements. Use only specialized low-ESR capacitors intended for switching regulator applications for the bulk capacitors. The bulk capacitor's ESR determines the output ripple voltage and the initial voltage drop after a high slew-rate transient. An aluminum electrolytic capacitor's ESR value is related to the case size with lower ESR available in larger case sizes. However, the equivalent series inductance of these capacitors increases with case size and can reduce the usefulness of the capacitor to high slew-rate transient loading. Unfortunately, ESL is not a specified parameter. Work with your capacitor supplier and measure the capacitor's impedance with frequency to select suitable components. In most cases, multiple electrolytic capacitors of small case size perform better than a single large case capacitor. For a given transient load magnitude, the output voltage transient response due to the output capacitor characteristics can be approximated by the following equation:
dI TRAN V TRAN = ESL x -------------------- + ESR x I TRAN dt
0.5 ESR () 0.4 0.3 0.2 0.1 10 100 CAPACITANCE (F) 1000
LE AB ON ST ATI ER OP
FIGURE 13. COUT2 OUTPUT CAPACITOR
load transient. The inductor value determines the converter's ripple current and the ripple voltage is a function of the ripple current. The ripple voltage and current are approximated by the following equations:
V IN - V OUT V OUT I = ------------------------------- x --------------V IN FS x LO
V OUT = I x ESR
Increasing the value of inductance reduces the ripple current and voltage. However, the large inductance values reduce the converter's response time to a load transient. One of the parameters limiting the converter's response to a load transient is the time required to change the inductor current. Given a sufficiently fast control loop design, the HIP6018 will provide either 0% or 100% duty cycle in response to a load transient. The response time is the time interval required to slew the inductor current from an initial current value to the post-transient current level. During this interval the difference between the inductor current and the transient current level must be supplied by the output capacitors. Minimizing the response time can minimize the output capacitance required. The response time to a transient is different for the application of load and the removal of load. The following equations give the approximate response time interval for application and removal of a transient load:
L O x I TRAN t RISE = ------------------------------V IN - V OUT L O x I TRAN t FALL = -----------------------------V OUT
Linear Output Capacitors
The output capacitors for the linear regulator and the linear controller provide dynamic load current. The linear controller uses dominant pole compensation integrated in the error amplifier and is insensitive to output capacitor selection. Capacitor, COUT3 should be selected for transient load regulation. The output capacitor for the linear regulator provides loop stability. The linear regulator (OUT2) requires an output capacitor characteristic shown in Figure 13. The upper line plots the 45 phase margin with 150mA load and the lower line is the 45 phase margin limit with a 10mA load. Select a COUT2 capacitor with characteristic between the two limits.
Output Inductor Selection
The PWM converter requires an output inductor. The output inductor is selected to meet the output voltage ripple requirements and sets the converter's response time to a
where: ITRAN is the transient load current step, tRISE is the response time to the application of load, and tFALL is the response time to the removal of load. With a +5V input source, the worst case response time can be either at the application or removal of load, and dependent upon the output voltage setting. Be sure to check both of these equations at the minimum and maximum output levels for the worst case response time.
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HIP6018
Input Capacitor Selection
The important parameters for the bulk input capacitor are the voltage rating and the RMS current rating. For reliable operation, select the bulk capacitor with voltage and current ratings above the maximum input voltage and largest RMS current required by the circuit. The capacitor voltage rating should be at least 1.25 times greater than the maximum input voltage and a voltage rating of 1.5 times is a conservative guideline. Use a mix of input bypass capacitors to control the voltage overshoot across the MOSFETs. Use ceramic capacitance for the high frequency decoupling and bulk capacitors to supply the RMS current. Small ceramic capacitors should be placed very close to the upper MOSFET to suppress the voltage induced in the parasitic circuit impedances. For a through hole design, several electrolytic capacitors (Panasonic HFQ series or Nichicon PL series or Sanyo MV-GX or equivalent) may be needed. For surface mount designs, solid tantalum capacitors can be used, but caution must be exercised with regard to the capacitor surge current rating. These capacitors must be capable of handling the surge-current at power-up. The TPS series available from AVX, and the 593D series from Sprague are both surge current tested. thermal resistance specifications. A separate heatsink may be necessary depending upon MOSFET power, package type, ambient temperature and air flow.
I O x r DS ( ON ) x V OUT I O x V IN x t SW x F S P UPPER = ----------------------------------------------------------- + ---------------------------------------------------V IN 2 I O x r DS ( ON ) x ( V IN - V OUT ) P LOWER = -------------------------------------------------------------------------------V IN
2 2
The rDS(ON) is different for the two previous equations even if the type device is used for both. This is because the gate drive applied to the upper MOSFET is different than the lower MOSFET. Figure 14 shows the gate drive where the upper gate-to-source voltage is approximately VCC less the input supply. For +5V main power and +12VDC for the bias, the gate-to-source voltage of Q1 is 7V. The lower gate drive voltage is +12VDC. A logic-level MOSFET is a good choice for Q1 and a logic-level MOSFET can be used for Q2 if its absolute gate-to-source voltage rating exceeds the maximum voltage applied to VCC .
+5V OR LESS +12V VCC
HIP6018
MOSFET Selection/Considerations
The HIP6018 requires 3 N-Channel power MOSFETs. Two MOSFETs are used in the synchronous-rectified buck topology of the PWM converter. The linear controller drives a MOSFET as a pass transistor. These should be selected based upon rDS(ON) , gate supply requirements, and thermal management requirements.
UGATE PHASE
Q1 NOTE: VGS VCC -5V Q2 CR1 NOTE: VGS VCC
-
+
LGATE PGND GND
PWM1 MOSFET Selection and Considerations
In high-current PWM applications, the MOSFET power dissipation, package selection and heatsink are the dominant design factors. The power dissipation includes two loss components; conduction loss and switching loss. These losses are distributed between the upper and lower MOSFETs according to duty factor (see the equations below). The conduction loss is the only component of power dissipation for the lower MOSFET. Only the upper MOSFET has switching losses, since the lower device turns on into near zero voltage. The equations below assume linear voltage-current transitions and do not model power loss due to the reverserecovery of the lower MOSFET's body diode. The gatecharge losses are proportional to the switching frequency (FS) and are dissipated by the HIP6018, thus not contributing to the MOSFETs' temperature rise. However, large gate charge increases the switching interval, tSW which increases the upper MOSFET switching losses. Ensure that both MOSFETs are within their maximum junction temperature at high ambient temperature by calculating the temperature rise according to package
FIGURE 14. OUTPUT GATE DRIVERS
Rectifier CR1 is a clamp that catches the negative inductor voltage swing during the dead time between the turn off of the lower MOSFET and the turn on of the upper MOSFET. The diode must be a Schottky type to prevent the lossy parasitic MOSFET body diode from conducting. It is acceptable to omit the diode and let the body diode of the lower MOSFET clamp the negative inductor swing, but efficiency might drop one or two percent as a result. The diode's rated reverse breakdown voltage must be greater than twice the maximum input voltage.
Linear Controller MOSFET Selection
The main criteria for selection of MOSFET for the linear regulator is package selection for efficient removal of heat. The power dissipated in a linear regulator is:
P LINEAR = I O x ( V IN - V OUT )
Select a package and heatsink that maintains the junction temperature below the maximum rating while operating at the highest expected ambient temperature.
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HIP6018 HIP6018 DC-DC Converter Application Circuit
Figure 15 shows an application circuit of a power supply for a microprocessor computer system. The power supply provides the microprocessor core voltage (VOUT1), the GTL bus voltage (VOUT3) and clock generator voltage (VOUT2) from +3.3VDC, +5VDC and +12VDC. For detailed information
+12VIN F1 +5VIN 15A GND
on the circuit, including a Bill-of-Materials and circuit board description, see Application Note AN9805. Also see Intersil's web page (http://www.intersil.com) or Intersil AnswerFAX (407-724-7800) document # 99805 for the latest information.
L1 1H C1-7 6x1000F + C16 1F C18 VCC 1 VIN2 + 20 12 7 OCSET1 1.1K POWERGOOD C19 1000F PGOOD 1000pF R2 C15 1F
+3.3VIN
24 23
UGATE1 PHASE1
Q1 HUF76143
L3 3.5H
VOUT1 (1.8 TO 3.5V)
Q3 RFD3055 VOUT3 (1.5V) + C43-46 4x1000F R13 10K + C47 270F R11 1.87K R12 10K
DRIVE3 FB3
22 15 16 19 HIP6018 21
LGATE1 PGND VSEN1
Q2 HUF76143
C24-36 + 7x1000F R4 4.99K R8 C40 0.68F
VOUT2 FB2 R14 10K
18 13 11
FB1
2.21K COMP1 C41 10pF C42 R10 R9 732K
VOUT2 (2.5V)
17
2200pF 160K VID0 VID1 VID2 VID3 VID4 8 6 5 4 3 2 14 GND 10 9 FAULT RT SS C48 0.039F
VID0 VID1 VID2 VID3 VID4
FIGURE 15. APPLICATION CIRCUIT
All Intersil semiconductor products are manufactured, assembled and tested under ISO9000 quality systems certification.
Intersil semiconductor products are sold by description only. Intersil Corporation reserves the right to make changes in circuit design and/or specifications at any time without notice. Accordingly, the reader is cautioned to verify that data sheets are current before placing orders. Information furnished by Intersil is believed to be accurate and reliable. However, no responsibility is assumed by Intersil or its subsidiaries for its use; nor for any infringements of patents or other rights of third parties which may result from its use. No license is granted by implication or otherwise under any patent or patent rights of Intersil or its subsidiaries.
For information regarding Intersil Corporation and its products, see web site http://www.intersil.com
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