View TPS64200_1006108.PDF datasheet online --- IC-ON-LINE

Datasheet File OCR Text:

www.ti.com
TPS64200, TPS64201 TPS64202, TPS64203
SLVS485 - AUGUST 2003
SOT23 STEP DOWN CONTROLLER
FEATURES D Step-Down Controller for Applications With
up to 95% Efficiency
D 1.8-V to 6.5-V Operating Input Voltage Range D Adjustable Output Voltage Range From 1.2 V D
to VI High Efficiency Over a Wide Load Current Range Dropout
D D D D
Low Power DSP Supply Digital Cameras Hard Disk Drives Portable Audio Players
DESCRIPTION
The TPS6420x are nonsynchronous step-down controllers that are ideally suited for systems powered from a 5-V or 3.3-V bus or for applications powered from a 1-cell Li-Ion battery or from a 2- to 4-cell NiCd, NiMH, or alkaline battery. These step-down controllers drive an external P-channel MOSFET allowing design flexibility. To achieve highest efficiency over a wide load current range, this controller uses a minimum on time, minimum off time control scheme and consumes only 20-A quiescent current. The minimum on time of typically 600 ns (TPS64203) allows the use of small inductors and capacitors. When disabled, the current consumption is reduced to less than 1 A. The TPS6420x is available in the 6-pin SOT23 (DBV) package and operates over a free air temperature range of -40C to 85C.
D 100% Maximum Duty Cycle for Lowest D D D D
Internal Softstart 20-A Quiescent Current (Typical) Overcurrent Protected Available in a SOT23 Package
APPLICATIONS D USB Powered Peripherals D Organizers, PDAs, and Handheld PCs
TYPICAL APPLICATION CIRCUIT
TPS64200
5V 10 F TPS64200 1 2 3 EN GND SW VIN 6 5 4 R1 620 k 47 F PosCap 6TPA47M Si5447DC 10 H 3.3 V / 2 A Rs = 33 m
100 90 80 70 Efficiency - % 60 50 40 30 20 10
EFFICIENCY vs LOAD CURRENT
VI = 4.2 V
FB ISENSE
ZHCS2000
R2 360 k
TA = 25C, VO = 3.3 V 0.001 0.01 0.1 IO - Load Current - A 1 10
0 0.0001
Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of Texas Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet.
PRODUCTION DATA information is current as of publication date. Products conform to specifications per the terms of Texas Instruments standard warranty. Production processing does not necessarily include testing of all parameters.
Copyright 2003, Texas Instruments Incorporated
TPS64200, TPS64201 TPS64202, TPS64203
SLVS485 - AUGUST 2003
www.ti.com
These devices have limited built-in ESD protection. The leads should be shorted together or the device placed in conductive foam during storage or handling to prevent electrostatic damage to the MOS gates.
ORDERING INFORMATION
PLASTIC SOT23-6(1) (2) (DBV) TPS64200DBVR TPS64201DBVR TPS64202DBVR OUTPUT VOLTAGE Adjustable 1.2 V to VI Adjustable 1.2 V to VI MINIMUM ON-TIME ON time = 1.6 s Variable minimum on time MINIMUM OFF-TIME OFF time = 600 ns OFF time = 600 ns OFF time = 300 ns OFF time = 600 ns MARKING PJAI PJBI PJCI PJDI
Adjustable Variable minimum on time 1.2 V to VI Adjustable TPS64203DBVR ON time = 600 ns 1.2 V to VI (1) The R suffix indicates shipment in tape and reel with 3000 units per reel. (2) The T suffix indicates a mini reel with 250 units per reel.
ABSOLUTE MAXIMUM RATINGS
over operating free-air temperature range unless otherwise noted(1) Supply voltage, VIN Voltage at EN, SW, ISENSE Voltage at FB Maximum junction temperature, TJ Operating free-air temperature, TA Storage temperature, Tsgt Lead temperature 1,6 mm (1/16 inch) from case for 10 seconds -0.3 V to 7 V -0.3 V to VIN -0.3 V to 3.3 V 150C -40C to 85C -65C to 150C 300C
(1) Stresses beyond those listed under "absolute maximum ratings" may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated under "recommended operating conditions" is not implied. Exposure to absolute-maximum-rated conditions for extended periods may affect device reliability.
PACKAGE DISSIPATION RATINGS
PACKAGE TA 255C POWER RATING DERATING FACTOR ABOVE TA = 25C 4 mW/C TA = 705C POWER RATING 220 mW TA = 855C POWER RATING 180 mW
SOT23-6 400 mW : The thermal resistance junction to ambient of the 6-pin SOT23 package is 250C/W. NOTE
RECOMMENDED OPERATING CONDITIONS
MIN Supply voltage at VIN Operating junction temperature 1.8 -40 NOM MAX 6.5 125 UNIT V C
2
www.ti.com
TPS64200, TPS64201 TPS64202, TPS64203
SLVS485 - AUGUST 2003
ELECTRICAL CHARACTERISTICS
VIN = 3.8 V, VO = 3.3 V, EN = VIN, TA = -40C to 85C (unless otherwise noted) SUPPLY CURRENT PARAMETER VI I(Q) Input voltage range Operating quiescent current IO = 0 mA EN = VI VFB 1.213 0.01 -2 90 Measured with circuit according to Figure 1 Measured with circuit according to Figure 1 VI = 3.8 V Measured with circuit according to Figure 1 VI = 3.8 V, VO = 3.3 V, IO = 1000 mA Measured with circuit according to Figure 1 VI = 3.8 V, VO = 1.2 V, IO = 800 mA IO = 0 mA, Time from active EN to VO, CO = 47 F VI 2.5 V VI = 1.8 V VI 2.5 V VI = 1.8 V 105 0.01 0.6 0.6 94% 80% 0.25 ms 0.2 +2 120 0.2 TEST CONDITIONS MIN 1.8 20 0.1 TYP MAX 6.5 35 1 VI UNIT V A A V V A % mV A %/V %/A
I(SD) Shutdown current OUTPUT/CURRENT LIMIT VO VFB Adjustable output voltage range Feedback voltage Feedback leakage current Feedback voltage tolerance V(ISENSE) Reference voltage for current limit ISENSE leakage current Line regulation Load regulation
Efficiency
Start-up time GATE DRIVER (SW-PIN)
4 6 4 6 150
rDS(ON) rDS(ON) IO ENABLE VIH VIL Ilkg V(UVLO)
P-channel MOSFET on-resistance N-channel MOSFET on-resistance Maximum gate drive output current, SW EN high level input voltage EN low level input voltage EN trip point hysteresis EN input leakage current Undervoltage lockout threshold
mA V 0.3 V mV 0.2 A V 1.84 0.74
Device is off Device is operating
1.3 115
EN = GND or VIN
0.01 1.7
ON TIME and OFF TIME TPS64200, TPS64201, TPS64202 ton Minimum on time Reduced on time 1 Reduced on time 2 Reduced on time 3 toff Minimum off time TPS64203 only TPS64201,TPS64202 TPS64201,TPS64202 TPS64201,TPS64202 TPS64200,TPS64201, TPS64203 TPS64202 only 0.44 0.24 1.36 0.56 1.6 0.65 0.80 0.40 0.20 0.55 0.3 0.66 0.36 s s s s s s s
3
TPS64200, TPS64201 TPS64202, TPS64203
SLVS485 - AUGUST 2003
www.ti.com
PIN ASSIGNMENTS
DBV PACKAGE (TOP VIEW)
EN GND FB
1 2 3
6 5 4
SW VIN ISENSE
Terminal Functions
TERMINAL NAME EN FB GND SW ISENSE VIN NO. 1 3 2 6 4 5 I/O I I I O I I DESCRIPTION Enable. A logic low enables the converter, logic high forces the device into shutdown mode reducing the supply current to less than 1 A. Feedback pin. Connect an external voltage divider to this pin to set the output voltage. Ground This pin connects to the gate of an external P-channel MOSFET. Current sense input. Connect the current sense resistor between VIN and ISENSE. (optional) Supply voltage input
FUNCTIONAL BLOCK DIAGRAM
VIN EN
105 mV ISense + _ Softstart FB + _
Overcurrent Comparator
Minimum ton Timer (0.2 s, 0.4 s, 0.8 s, 1.6 s)
Logic M U X
Regulation Comparator
Minimum toff Timer (0.6 s, 0.3 s,)
Driver R Q S
SW
Vref
ton Regulation Timer (3 s, 15 s, 16 s)
ton Regulator
GND
4
www.ti.com
TPS64200, TPS64201 TPS64202, TPS64203
SLVS485 - AUGUST 2003
TYPICAL CHARACTERISTICS
All graphs were generated using the circuit as shown unless otherwise noted. For output voltages other than 3.3 V, the output voltage divider was changed accordingly. Graphs for the TPS64203 were taken using the application circuit shown in Figure 25.
VI R(ISENSE) = 33 m CI 10 F X7R TPS6420x 1 2 3 EN GND SW VIN 6 5 CDRH 103R- 100 4 10 H MBRM120LT3 R1 620 k Cff 4.7 pF VO Co 47 F PosCap 6TPA47M Si5447DC
FB ISENSE
R2 360 k
Figure 1. Basic Application Circuit For a 2-A Step-Down Converter
TABLE OF GRAPHS
FIGURE Efficiency Output voltage Switching frequency Operating quiescent current Output voltage ripple Line transient response Load transient response Start-up timing Using circuit according to Figure 1 Using circuit according to Figure 1 Using circuit according to Figure 1 vs Load current vs Output current vs Output current vs Input voltage 2-5 6-9 10 - 13 14 15 16 17 18
5
TPS64200, TPS64201 TPS64202, TPS64203
SLVS485 - AUGUST 2003
www.ti.com
TPS64200
TPS64201
EFFICIENCY vs LOAD CURRENT
100 90 80 70 Efficiency - % 60 50 40 30 20 10 0 0.0001 0.001 0.01 0.1 IO - Load Current - A TA = 25C, VO = 3.3 V 1 10 VI = 6 V VI = 4.2 V VI = 5 V Efficiency - % VI = 3.6 V 100 90 80 70 60
EFFICIENCY vs LOAD CURRENT
VI = 3.6 V VI = 4.2 V VI = 5 V VI = 6 V 50 40 30 20 10 0 0.0001 0.001 0.01 0.1 IO - Load Current - A TA = 25C, VO = 3.3 V 1 10
Figure 2
TPS64202
Figure 3
TPS64203
EFFICIENCY vs LOAD CURRENT
100 VI = 3.6 V 90 80 70 Efficiency - % 60 50 40 30 20 10 0 0.0001 TA = 25C, VO = 3.3 V 0.001 0.01 0.1 IO - Load Current - A 1 10 VI = 4.2 V VI = 5 V VI = 6 V Efficiency - % 90 80 70 60 50 40 30 20 10 0 0.0001 0.001 100 TA = 25C, VO = 1.2 V
EFFICIENCY vs LOAD CURRENT
VI = 1.8 V VI = 2.5 V
VI = 3.6 V VI = 6 V VI = 5 V
0.01 0.1 IO - Load Current - A
1
10
Figure 4
Figure 5
6
www.ti.com
TPS64200, TPS64201 TPS64202, TPS64203
SLVS485 - AUGUST 2003
TPS64200
TPS64201
OUTPUT VOLTAGE vs OUTPUT CURRENT
3.40 3.38 3.36 VO - Output Voltage - V 3.34 3.32 3.30 3.28 3.26 3.24 3.22 3.20 0.0001 0.001 0.01 0.1 IO - Output Current - A 1 10 VI = 3.6 V VI = 6 V TA = 25C, VO = 3.3 V VI = 5 V VI = 4.2 V VO - Output Voltage - V 3.40 3.38 3.36 3.34 3.32 3.30 3.28 3.26 3.24 3.22 3.20 0.0001 TA = 25C, VO = 3.3 V
OUTPUT VOLTAGE vs OUTPUT CURRENT
VI = 6 V
VI = 5 V VI = 4.2 V
VI = 3.6 V
0.001
0.01 0.1 IO - Output Current - A
1
10
Figure 6
TPS64202
Figure 7
TPS64203
OUTPUT VOLTAGE vs OUTPUT CURRENT
3.40 3.38 3.36 VO - Output Voltage - V 3.34 3.32 3.30 3.28 3.26 3.24 3.22 3.20 0.0001 1.17 1.15 0.0001 VI = 3.6 V VI = 4.2 V VO - Output Voltage - V TA = 25C, VO = 3.3 V 1.29 VI = 6 V VI = 5 V 1.27 1.25 1.23 1.21 1.19 TA = 25C, VO = 1.2 V
OUTPUT VOLTAGE vs OUTPUT CURRENT
VI = 3.6 V
VI = 5 V VI = 6 V
VI = 1.8 V
VI = 2.5 V
0.001
0.01 0.1 IO - Output Current - A
1
10
0.001
0.01 0.1 IO - Output Current - A
1
10
Figure 8
Figure 9
7
TPS64200, TPS64201 TPS64202, TPS64203
SLVS485 - AUGUST 2003
www.ti.com
TPS64200
TPS64201
SWITCHING FREQUENCY vs OUTPUT CURRENT
400 VI = 5 V 350 300 f - Frequency - kHz 250 200 150 100 100 50 0 0.001 50 0.01 0.1 1 10 0 0.001 VO = 1.2 V f - Frequency - kHz 350 300 250 200 150 VO = 3.3 V 500
SWITCHING FREQUENCY vs OUTPUT CURRENT
VO = 3.3 V 450 400 VI = 5 V
VO = 1.2 V
0.01
0.1
1
10
IO - Output Current - A
IO - Output Current - A
Figure 10
TPS64202
Figure 11
TPS64203
SWITCHING FREQUENCY vs OUTPUT CURRENT
600 550 500 450 f - Frequency - kHz f - Frequency - kHz 400 350 300 250 200 150 100 50 VO = 3.3 V 0.01 0.1 1 10 0 0.001 VI = 3.8 V, Cff = 165 pF 700 600 500 400 300 200 100 VI = 3.8 V VI = 4.2 V 900 VI = 5 V 800
SWITCHING FREQUENCY vs OUTPUT CURRENT
VO = 3.3 V, Cff = 165 pF
VO = 1.2 V
0 0.001
IO - Output Current - A
0.01 0.1 1 IO - Output Current - A
10
Figure 12
Figure 13
8
www.ti.com
TPS64200, TPS64201 TPS64202, TPS64203
SLVS485 - AUGUST 2003
TPS642000
OPERATING QUIESCENT CURRENT vs INPUT VOLTAGE
40 IQ - Operating Quiescent Current - A 35 TA = 25C 30 TA = -40C 25 20 TA = 85C 20 mV/Div
TPS64200
OUTPUT VOLTAGE RIPPLE
VI = 3.8 V, VO = 1.2 V, RL = 1.2 , TA = 25C IO = 1000 mA
VO
I(coil) 15 10 5 0 200 mA/Div 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 5.5 6 VI - Input Voltage - V 6.5 2 ms/Div
Figure 14
TPS64200
Figure 15
TPS64203
LINE TRANSIENT RESPONSE
VI = 3.8 V to 5 V, VO = 1.2 V, RL = 1.2 , TA = 25C
LOAD TRANSIENT RESPONSE
IO 1 A/Div VI
1 V/Div
20 mV/Div
VO 50 mV/Div VO
VI = 5 V, VO = 3.3 V, IL = 200 mA to 1800 mA, TA = 25C
40 ms/Div
50 ms/Div
Figure 16
Figure 17
9
TPS64200, TPS64201 TPS64202, TPS64203
SLVS485 - AUGUST 2003
www.ti.com
TPS64200
STARTUP TIMING
EN VO II
I(Inductor)
VI = 3.8 V, VO = 3.3 V, RL = 1.66 , TA = 25C 100 ms/Div
Figure 18
DETAILED DESCRIPTION Operation
The TPS6420x is a nonsynchronous step-down controller which is operating with a minimum on-time/minimum off-time control. An external PMOS is turned on until the output voltage reaches its nominal value or the current limit is exceeded. If the current limit is exceeded, the PMOS is switched off and stays off for the minimum off-time. After that the PMOS is switched on again. When the nominal output voltage is reached, the PMOS is switched off and stays off until the output voltage dropped below its nominal value.
Operating Modes
When delivering low or medium output current, the TPS6420x operate in discontinuous mode. With every switching cycle, the current in the inductor starts at zero, rises to a maximum value and ramps down to zero again. As soon as the current in the inductor drops to zero, ringing occurs at the resonant frequency of the inductor and stray capacitance, due to residual energy in the inductor when the diode turns off. Ringing in discontinuous mode is normal and does not have any influence on efficiency. The ringing does not contain much energy and can easily be damped by an RC snubber. See the application section for further details. With high output current, the TPS6420x operate in continuous current mode. In this mode, the inductor current does not drop to zero within one switching cycle. The output voltage in continuous mode is directly dependant on the duty cycle of the switch.
Variable Minimum On-Time (TPS64201 to TPS64203 Only)
The minimum on-time of the device is 1.6 s. At light loads, this would cause a low switching frequency in the audible range because the energy transferred to the output during the on-time would cause a higher rise in the output voltage than needed and therefore lead to a long off-time until the output voltage dropped again. To avoid a switching frequency in the audible range the TPS64201, TPS64202, and TPS64203 can internally reduce the minimum on time in three steps from 1.6 s to 800 ns, 400 ns and 200 ns. The on-time is reduced by one step if the switching frequency dropped to a lower value than 50 kHz. This keeps the frequency above the audio frequency over a wide load range and also keeps the output voltage ripple low.
10
www.ti.com
TPS64200, TPS64201 TPS64202, TPS64203
SLVS485 - AUGUST 2003
Soft Start
The TPS6420x has an internal soft start circuit that limits the inrush current during start up. This prevents possible voltage drops of the input voltage in case a battery or a high impedance power source is connected to the input of the TPS6420x. During soft start the current limit is increased from 25% of its maximum to the maximum within about 250 s.
100% Duty Cycle Low Dropout Operation
The TPS6420x offers the lowest possible input to output voltage difference while still maintaining regulation with the use of the 100% duty cycle mode. In this mode the P-channel switch is constantly turned on. This is particularly useful in battery powered applications to achieve longest operation time by taking full advantage of the whole battery voltage range.
Enable
A voltage higher than the EN trip point of 1.3 V up to the input voltage forces the TPS64200 into shutdown. In shutdown, the power switch, drivers, voltage reference, oscillator, and all other functions are turned off. The supply current is reduced to less than 1 A in shutdown. Pulling enable low starts up the TPS64200 with the softstart as described under the chapter softstart.
Undervoltage Lockout
The undervoltage lockout circuit prevents the device from misoperation at low input voltages. Basically, it prevents the converter from turning on the external PMOS under undefined conditions.
Current Limit
The ISENSE input is used to set the current limit for the external PMOS. The sense resistor must be connected between VI and source of the external PMOS. The ISENSE pin is connected to the source of the external PMOS. The maximum current is calculated by: V I (cur lim) + (ISENSE) R S (1)
For low cost solutions the rDS(on) of the external PMOS can also be used to set the current limit. In this case the ISENSE pin is connected to the drain of the PMOS. The current in the PMOS is automatically sampled by the TPS6420x some 10 ns after the PMOS is turned on. The ISENSE pin should always be connected to either the source of the PMOS or the drain if an additional sense resistor is used. Otherwise there is no working overcurrent protection and no soft start in the system. The maximum drain current if the rDS(on) is used as a sense resistor is calculated by: V I (cur lim) + (ISENSE) r DS(on) (2)
Short-Circuit Protection
With a controller only limited short circuit protection is possible because the temperature of the external components is not supervised. In an overload condition, the current in the external diode may exceed the maximum rating. To protect the diode against overcurrent, the off-time of the TPS6420x is increased when the voltage at the feedback pin is lower than its nominal value. The off-time when the output is shorted (feedback voltage is zero) is about 4 s. This allows the current in the external diode to drop until the PMOS is turned on again and the overcurrent protection switches off the PMOS again. The off-time is directly proportional to the voltage at feedback.
11
TPS64200, TPS64201 TPS64202, TPS64203
SLVS485 - AUGUST 2003
www.ti.com
THEORY OF OPERATION
The basic application circuit for the TPS64200 is shown in Figure 1. External component selection is driven by the load requirement. It begins with the selection of the current sense resistor R(ISENSE) followed by the output diode, the inductor L, and the output and input capacitors. The inductor is chosen based on the desired amount of ripple current and switching frequency. The output capacitor is chosen large enough to meet the required output ripple and transient requirements. The ESR of the output capacitor is needed for stability of the converter. Therefore, an output capacitor with a certain amount of ESR is needed for the standard application circuit. See the application information for more details. The input capacitor must be capable of handling the required RMS input current.
Setting the Inductor Current Limit
The ISENSE pin is connected to an internal current comparator with a threshold of 120 mV/R(ISENSE). The current comparator sets the peak inductor current. As the current limit is intended to protect the external PMOS the limit must not be reached in normal operation. Set the current limit to about 1.3 times the maximum output current or higher if desired. This takes into account a certain amount of inductor current ripple. The current limit may also influence the start-up time when the current limit is exceeded during start up. V R (ISENSE) v min IO -- maximum output current in continuous conduction mode (ISENSE) V(ISENSE), min = 90 mV 1.3 I (3) O
2
The current sense resistor's power rating should be: V P (ISENSE) w (ISENSE) R (ISENSE) max V(ISENSE), max = 120 mV (4)
Setting the Output Voltage
The output voltage of the TPS64200 to TPS64202 can be set using an external resistor divider. The sum of R1 and R2 should not exceed 1 M to keep the influence of leakage current into the feedback pin low. V O +V FB R1 ) R2 R2 R1 + R2 V V O * R2 with VFB = 1.2 V (5)
FB
In some applications, depending on the layout, the capacitance may be too high from FB to GND. In this case, the internal comparator may not switch fast enough to operate with the minimum on-time or the minimum off-time given in this data sheet. For such applications a feedforward capacitor (Cff) in the range of 4.7 pF to 47 pF (typical) is added in parallel with R1 to speed up the comparator. Choose a capacitor value that is high enough that the device turns on the PMOS for its minimum on-time with no load at the output.
Selecting the Input Capacitor
The input capacitor is used to reduce peak currents drawn from the power source and reduces noise and voltage ripple on the input of the converter, caused by its switching action. Use low ESR tantalum capacitors or preferably X5R or X7R ceramic capacitors with a voltage rating higher than the maximum supply voltage in the application. In continuous conduction mode, the input capacitor must handle an rms-current which is given by: I [I O V , min I V (6)
Cin(rms)
O
Select the input capacitor according to the calculated rms-input current requirements and according to the maximum voltage ripple. Use a minimum value of 10 F: 1L 1L 0.3 DI 2 L 2 C , min + [ I V V V (ripple) I (ripple)
12 2 2
O V I
I
with: V(ripple) - voltage ripple at CI IL - inductor current ripple
(7)
www.ti.com
TPS64200, TPS64201 TPS64202, TPS64203
SLVS485 - AUGUST 2003
For a first approximation use: L = 10 H V(ripple) = 150 mV (verify in the application)
Selecting the Inductor Value
The main parameters when choosing the inductor are current rating and inductance. The inductance mainly determines the inductor current ripple. The TPS6420x operates with a wide range of inductor values. Values between 4.7 H and 47 H work in most applications. Select an inductor with a current rating exceeding the limit set by R(ISENSE) or rDS(on). The first step in inductor design is to determine the operating mode of the TPS64200. The device can either work with minimum-on-time or minimum-off-time, depending on input voltage and output voltage. The device works with minimum-on-time if: t V *V *I I O O r DS(on) *R RL xI O w off , min V O )V SCHOTTKY t on, min )R RL I O (8)
with RRL - inductor resistance with L+V DI Dt
For minimum-on-time: V -V -I I OO r -R DS(on) RL DI I O t on, min with: I 0.3 x IO (9)
L+
For minimum-off-time: V L+ O )V SCHOTTKY )R DI Table 1. List of Inductors Tested With the TPS6420x
MANUFACTURER TDK TDK Sumida Sumida Sumida Sumida Coilcraft Coilcraft Coilcraft Wurth Wurth TYPE SLF7032T-100M1R4 SLF6025-150MR88 CDRH6D28-5R0 CDRH103R-100 CDRH4D28-100 CDRH5D18-6R2 DO3316P-472 DT3316P-153 DT3316P-223 744 052 006 74451115 INDUCTANCE 10 H 20% 15 H 20% 5 H 10 H 10 H 6.2 H 4.7 H 15 H 22 H 6.2 H 15 H DC RESISTANCE 53 m 20% 85 m 20% 23 m 45 m 95 m 71 m 18 m 60 m 84 m 80 m 90 m SATURATION CURRENT 1.4 A 0.88 A 2.4 A 2.4 A 1.0 A 1.4 A 5.4 A 1.8 A 1.5 A 1.45 A 0.8 A
RL
I
O
t
off
, min (10)
13
TPS64200, TPS64201 TPS64202, TPS64203
SLVS485 - AUGUST 2003
www.ti.com
Selecting the External PMOS
An external PMOS must be used for a step-down converter with the TPS64200. The selection criteria for the PMOS are threshold voltage, rDS(on), gate charge and current and voltage rating. Since the TPS64200 can operate down to 1.8 V, the external PMOS must have a VGS(th) much lower than that if it is operated with such a low voltage. As the gate of the PMOS finds the full supply voltage applied to the TPS64200, the PMOS must be able to handle that voltage at the gate. The drain to source breakdown voltage rating should be at least a few volts higher than the supply voltage in the application. The rms-current in the PMOS assuming low inductor current ripple and continuous conduction mode, is: I [I D+I V O O V I (11)
PMOS(rms)
O
The power dissipated in the PMOS is comprised of conduction losses and switching losses. The conduction losses are a function of the rms-current in the PMOS and the rDS(on) at a given temperature. They are calculated using:
2 2
P
(cond)
+I
O
D
r
DS(on)
1 ) TC
T -25C J
[I
O
D
r
DS(on)
(12)
with TC = 0.005/C Table 2. PMOS Transistors Used in the Application Section
TYPE Si5447DC Si5475DC Si2301ADS FDG326P MANUFACTURER Vishay Siliconix Vishay Siliconix Vishay Siliconix Fairchild rDS(on) 0.11 at VGS = -2.5 V 0.041 at VGS = -2.5 V 0.19 at VGS = -2.5 V 0.17 at VGS = -2.5 V VDS -20 V -12 V -20 V -20 V ID -3.5 A at 25C -6.6 A at 25C -1.4 A at 25C -1.5 A PACKAGE 1206 1206 SOT23 SC70
Selecting the Output Diode
The output diode conducts in the off phase of the PMOS and carries the full output current. The high switching frequency demands a high-speed rectifier. Schottky diodes are recommended for best performance. Make sure that the peak current rating of the diode exceeds the peak current limit set by the sense resistor R(ISENSE) or rDS(on). Select a Schottky diode with a low reverse leakage current to avoid an increased supply current. The average current in the diode in continuous conduction mode, assuming low inductor current ripple, is: I V [ I (1-D) + I 1- O (diode)(Avg) O O V I Table 3. Tested Diodes
TYPE MBRM120LT3 MBR0530T1 ZHCS2000TA B320 MANUFACTURER On Semiconductor On Semiconductor Zetex Diodes Inc. VR 20 V 30 V 40 V 20 V IF 1A 0.5 A 2A 3A PACKAGE DO216AA SOD123 SOT23-6 SMA
(13)
14
www.ti.com
TPS64200, TPS64201 TPS64202, TPS64203
SLVS485 - AUGUST 2003
Selecting the Output Capacitor
The value of the output capacitor depends on the output voltage ripple requirements as well as the maximum voltage deviation during a load transient. The TPS6420x require a certain ESR value for proper operation. Low ESR tantalum capacitors or PosCap work best in the application. A ceramic capacitor with up 1 F may be used in parallel for filtering short spikes. The output voltage ripple is a function of both the output capacitance and the ESR value of the capacitor. For a switching frequency which is used with the TPS6420x, the voltage ripple is typically between 90% and 95% due to the ESR value. DV pp + DI ESR ) DV pp 1 C O [ 1.1 DI ESR (14)
8
ESR, max [
(15) 1.1 DI The output capacitance typically increases with load transient requirements. For a load step from zero output current to its maximum, the following equation can be used to calculate the output capacitance: L DI
2
O C+ O (V * V ) x DV I O Table 4. Capacitors Used in the Application
TYPE 6TPA47m (PosCap) T491D476M010AS B45197A B45294-R1 107-M40 594D476X0016C2 MANUFACTURER Sanyo Kemet Epcos Epcos Vishay CAPACITANCE 47 F 47 F 47 F 100 F 47 F ESR 0.1 0.8 0.175 0.045 0.11 VOLTAGE RATING 6.3 V 10 V 16 V 6.3 V 16 V
(16)
Output Voltage Ripple
Output voltage ripple causes the output voltage to be higher or lower than set by the resistor divider at the feedback pin. If the application runs with minimum on-time, the ripple (half of the peak-to-peak value) adds to the output voltage. In an application which runs with minimum off-time, the output voltage is lower by the amount of ripple (half of the peak-to-peak value) at the output.
Snubber Design
For low output current, the TPS6420x work in discontinuous current mode. When the current in the inductor drops to zero, the inductor and parasitic capacitance form a resonant circuit, which causes oscillations when both, diode and PMOS do not conduct at the end of each switching cycle. The oscillation can easily be damped by a RC-snubber. The first step in the snubber design is to measure the oscillation frequency of the sine wave. Then, a capacitor has to be connected in parallel to the Schottky diode which causes the frequency to drop to half of its original value. The resistor is selected for optimum transient response (aperiodic). R + 2pfL f - measured resonant frequency L - inductance used (17)
Selecting the Right Device for the Application
The TPS6420x step-down controllers either operate with a fixed on-time or a fixed off-time control. It mainly depends on the input voltage to output voltage ratio if the switching frequency is determined by the minimum-on-time or the minimum-off-time. To select the right device for an application see the table below:
INPUT TO OUTPUT VOLTAGE RATIO VI >> VO (e.g. VI = 5 V VO = 1.5 V) VI VO (e.g. VI = 3.8 V VO = 3.3 V) SWITCHING FREQUENCY DETERMINED BY Minimum on-time Minimum off-time PROPOSED DEVICE FOR HIGH SWITCHING FREQUENCY TPS64203 TPS64202 PROPOSED DEVICE FOR LOW SWITCHING FREQUENCY TPS64200, TPS64201 TPS64200, TPS64201 15
TPS64200, TPS64201 TPS64202, TPS64203
SLVS485 - AUGUST 2003
www.ti.com
APPLICATION INFORMATION
Li-lon 3.3 V to 4.2 V CIN 10 F 1 2 3
R(ISENSE) = 33 m TPS64202 EN GND SW VIN 6 5 4 CDRH6D28-5R0 5 H MBRM120LT3 R1 620 k Cff 4.7 pF 3.3 V / 2 A Co 47 mF PosCap 6TPA47M Si5475DC
FB ISENSE
R2 360 k
Figure 19. Application For a Li-Ion to 3.3-V / 2-A Conversion The TPS64202 was used for this application because for a low input to output voltage difference, the switching frequency is determined by the minimum off-time. The TPS64202 with its minimum off-time of 300 ns provides a higher switching frequency compared to the other members of the TPS6420x family.
Li-lon 3.3 V to 4.2 V CIN 10 F 1 2 3
TPS64202 EN GND SW VIN 6 5 4 Si5475DC
FB ISENSE
CDRH6D28-5R0 5 H R1 620 k R3 150 3.3 V / 2 A Cff 4.7 pF Co 47 mF PosCap 6TPA47M
MBRM120LT3
C3 470 pF
R2 360 k
Figure 20. Application For a Li-Ion to 3.3-V / 2-A Conversion Using rDS(on) Sense and RC Snubber Network For the Schottky Diode
16
www.ti.com
TPS64200, TPS64201 TPS64202, TPS64203
SLVS485 - AUGUST 2003
DESIGN EXAMPLE FOR AN APPLICATION USING A LI-ION CELL (3.3 V TO 4.2 V) TO GENERATE 3.3 V/500 mA
1. Calculate the sense resistor for the current limit: V R (ISENSE) v min (ISENSE) + 90 mV + 138 mW 1.3 I 1.3 0.5 A O (18)
Choose the next lower standard value : R(ISENSE) = 120 m. Verify the inductor current ripple after the inductor has been determined in step 5. If the rDS(on) of the PMOS is used to sense the inductor current, a PMOS with less than 138 m must be used for the application. 2. Calculate the resistors for the output voltage divider using VO = 3.3 V and VFB = 1.21 V R1 + R2 V V O -R2 + 1.72 R2 (19)
FB
Choose R1 = 360 k, and then get R2 = 619 k. Select the next standard value: R2 = 620 k 3. Select the external PMOS For a Li-Ion to 3.3-V conversion, the minimum input voltage is 3.3 V. Therefore, the converter runs in 100% mode (duty cycle=1) and the maximum PMOS current is equal to the output current. I (PMOS) +I O + 0.5 A (20)
The Si2301ADS is selected for this application because it meets the requirements when an external sense resistor is used. Otherwise a PMOS with less rDS(on) must be selected. Verify the maximum power dissipation of the PMOS using:
2
P
(cond)
+I
O
r
DS(on)
+ (0.5 A) 2
0.19 W + 48 mW
(21)
4. Select the external diode For the Schottky diode, the worst case current is at high input voltage (4.2 V for a Li-Ion cell). I [I V 1- O O V I +I 1- 3.3 V + 0.11 A 4.2 V (22)
(diode)(Avg)
O
The MBR0530T1 is selected because it meets the voltage and current requirements. The forward voltage is about 0.3 V. Do not use a Schottky diode which is much larger than required as it also typically has more leakage current and capacitance which reduces efficiency. 5. Calculate the inductor value. If the output voltage is close to the input voltage, the switching frequency is determined by the minimum off-time. Therefore, the TPS64202 is used for the maximum switching frequency possible. Allow an inductor ripple current of 0.3 x IO for the application. For the inductor, a series resistance of 100 m is assumed. For minimum-off-time, the inductor value is: (23) V L+ O )V (SCHOTTKY) )R DI RL I O t off , min + (3.3 V ) 0.3 V ) 0.05 V) 0.3 0.5 A 0.3 ms + 7.3 mH
For a low inductor current ripple, select the next available larger inductor with L = 10 H. This provides an inductor ripple current of 110 mA (peak-to-peak).
17
TPS64200, TPS64201 TPS64202, TPS64203
SLVS485 - AUGUST 2003
www.ti.com
V DI +
O
)V
(SCHOTTKY)
)R L
RL
I
O
t
off
, min + 110 mA (24)
The current rating for the inductor must be: I, inductor u I O ) DI + 555 mA 2 (25)
6. Select the input and output capacitor The output capacitor is selected for an output voltage ripple of less than 20 mVpp. With ESR, max [ DV pp 1.1 DI + 0.02 V + 165 mW 0.11 A (26)
1.1
A 47-F PosCap with an ESR of 100 m was selected to meet the ripple requirements. The input capacitor was selected to its minimum value of 10 F.
1 Li-lon Cell R(ISENSE) = 120 m TPS64202 1 2 3 EN GND SW VIN 6 5 4 CDRH4D18-100 10 H MBR0530T1 R1 620 k 3.3 V / 0.5 A Si2301DS
10 F
FB ISENSE
47 F PosCap 6TPA47M R2 360 k
Figure 21. Application Circuit
18
www.ti.com
TPS64200, TPS64201 TPS64202, TPS64203
SLVS485 - AUGUST 2003
5V R(ISENSE) = 33 m TPS64200 1 2 3 EN GND SW VIN 6 5 4 CDRH103R-100 10 H ZHCS200 R1 620 k 3.3 V / 2 A Si5447DC
10 F
FB ISENSE
47 mF PosCap 6TPA47M R2 360 k
Figure 22. Application For a 5-V to 3.3-V / 2-A Conversion
Inverter Using TPS64200
VI 2.7 V to 4.2 V 10 F 1 2 3 R(ISENSE) = 33 m TPS64200 EN GND SW VIN 6 5 MBR0530T1 4 SW R2 24 k VI _ OPA363 + R1 100 k CDRH4D28-100 10 H 47 F X7R -5 V / 0.1 A Si2301DS
FB ISENSE
Figure 23. Application For an Inverter Using TPS64200
19
TPS64200, TPS64201 TPS64202, TPS64203
SLVS485 - AUGUST 2003
www.ti.com
The TPS6420x can be used for an inverter. Only one additional operational amplifier is required for this application. When the PMOS is switched on, the current in the inductor ramps up to its maximum, set by Rs. Then the PMOS is switched off, the energy stored in the inductor is transferred to the output. The output voltage and the maximum output current can be calculated using: V + R1 O R2 V I max [ 0.8 V -V I O (ISENSE) 2R (ISENSE) V (27)
FB
O
OLED Power Supply
The TPS6420x can be combined with a TPS61045 boost converter for a OLED power supply.
4.7 H 7 V / 50 mA 4.7 F 1L SW 2 VIN DO 5 FB CTRL 6 GND PGND TPS61045 VI 1.8 V to 5.5 V 10 F 1 2 3 8 3 4 7 12 k 56 k 22 pF 1 F X7R
R(ISENSE) = 150 m TPS64200 EN GND SW VIN 6 5 MBR0530T1 4 SW R2 130 k VI _ OPA363 + R1 750 k CDRH4D28-100 10 H 47 F X7R -7 V / 50 mA Si2301DS
FB ISENSE
Figure 24. Application For a OLED Power Supply
20
www.ti.com
TPS64200, TPS64201 TPS64202, TPS64203
SLVS485 - AUGUST 2003
5V
10 F X5R 1 2 3
TPS64203 EN GND SW VIN 6 5 4 Wurth 744052006 6.2 H MBRM120LT3 100 F/6.3 V B45294-R1107-M40 1.2 V / 1.2 A Si2323DS
FB ISENSE
Figure 25. Application For a 5-V to 1.2-V / 1.2-A Conversion
5V R(ISENSE) = 33 m CIN 22 F 1 2 3 TPS64202 EN GND SW VIN 6 5 4 Si5475DC
FB ISENSE
DO3316P-472 4.7 H B320 R1 620 k Cff 4.7 pF Co 100 mF PosCap 6TPC100M 3.3 V / 3 A
R2 360 k
Figure 26. Application For a 5-V to 3.3-V / 3-A Conversion
21
TPS64200, TPS64201 TPS64202, TPS64203
SLVS485 - AUGUST 2003
www.ti.com
Ceramic Output Capacitor
5V R(ISENSE) = 33 m CI 10 F 1 2 3 TPS64203 EN GND SW VIN 6 5 R(GATE) 10 Si5475DC
4 FB ISENSE
CDRH6D28-100 10 H R1a 680 k R1b 2.2 M 3.3 V / 2 A Cff 82 pF Co 22 F X5R 6.3 V
MBRM120LT3
R2 300 k
Figure 27. Application Using a Ceramic Output Capacitor The control scheme of the TPS6420x usually requires an output capacitor with some tens of milliohms of ESR for stability, which is usually the case for tantalum capacitors. This application circuit above also works with ceramic capacitors. Resistor R1b is used to add an additional control signal to the feedback loop, which is coupled into the FB pin. The circuit works best with R1b = 2 ...4 x R1a. If the resistance of R1b is too low compared to R1a, the more load regulation the output voltage shows, but stability is best. The advantage of this circuit is a very low output voltage ripple and small size. The gate resistor shown can be used in every application. It minimizes switching noise of the converter and, therefore, increases stability and provides lower output voltage ripple. However, it decreases efficiency slightly because the rise and fall time, and the associated losses are larger. R1 + 1 1)1 R1a R1b R1b + 1 1- 1 R1 R1a (28)
Use the following equation to calculate R1a if R1b = 4R1a R1a + 5 R1 4 (29)
22
MECHANICAL DATA
MPDS026D - FEBRUARY 1997 - REVISED FEBRUARY 2002
DBV (R-PDSO-G6)
PLASTIC SMALL-OUTLINE
0,95 6 4
6X
0,50 0,25
0,20 M
1,70 1,50
3,00 2,60
0,15 NOM
1 3,00 2,80
3
Gage Plane
0,25 0-8 0,55 0,35
Seating Plane 1,45 0,95 0,05 MIN 0,10
4073253-5/G 01/02
NOTES: A. B. C. D.
All linear dimensions are in millimeters. This drawing is subject to change without notice. Body dimensions do not include mold flash or protrusion. Leads 1, 2, 3 may be wider than leads 4, 5, 6 for package orientation.
POST OFFICE BOX 655303
* DALLAS, TEXAS 75265
1
IMPORTANT NOTICE Texas Instruments Incorporated and its subsidiaries (TI) reserve the right to make corrections, modifications, enhancements, improvements, and other changes to its products and services at any time and to discontinue any product or service without notice. Customers should obtain the latest relevant information before placing orders and should verify that such information is current and complete. All products are sold subject to TI's terms and conditions of sale supplied at the time of order acknowledgment. TI warrants performance of its hardware products to the specifications applicable at the time of sale in accordance with TI's standard warranty. Testing and other quality control techniques are used to the extent TI deems necessary to support this warranty. Except where mandated by government requirements, testing of all parameters of each product is not necessarily performed. TI assumes no liability for applications assistance or customer product design. Customers are responsible for their products and applications using TI components. To minimize the risks associated with customer products and applications, customers should provide adequate design and operating safeguards. TI does not warrant or represent that any license, either express or implied, is granted under any TI patent right, copyright, mask work right, or other TI intellectual property right relating to any combination, machine, or process in which TI products or services are used. Information published by TI regarding third-party products or services does not constitute a license from TI to use such products or services or a warranty or endorsement thereof. Use of such information may require a license from a third party under the patents or other intellectual property of the third party, or a license from TI under the patents or other intellectual property of TI. Reproduction of information in TI data books or data sheets is permissible only if reproduction is without alteration and is accompanied by all associated warranties, conditions, limitations, and notices. Reproduction of this information with alteration is an unfair and deceptive business practice. TI is not responsible or liable for such altered documentation. Resale of TI products or services with statements different from or beyond the parameters stated by TI for that product or service voids all express and any implied warranties for the associated TI product or service and is an unfair and deceptive business practice. TI is not responsible or liable for any such statements. Following are URLs where you can obtain information on other Texas Instruments products and application solutions: Products Amplifiers Data Converters DSP Interface Logic Power Mgmt Microcontrollers amplifier.ti.com dataconverter.ti.com dsp.ti.com interface.ti.com logic.ti.com power.ti.com microcontroller.ti.com Applications Audio Automotive Broadband Digital Control Military Optical Networking Security Telephony Video & Imaging Wireless Mailing Address: Texas Instruments Post Office Box 655303 Dallas, Texas 75265 Copyright 2003, Texas Instruments Incorporated www.ti.com/audio www.ti.com/automotive www.ti.com/broadband www.ti.com/digitalcontrol www.ti.com/military www.ti.com/opticalnetwork www.ti.com/security www.ti.com/telephony www.ti.com/video www.ti.com/wireless

▲Up To Search▲

Price & Availability of TPS64200

	To Download TPS64200 Datasheet File
If you can't view the Datasheet, Please click here to try to view without PDF Reader .