Texas Instruments TPS54331D, TPS54331 Datasheet

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0.01 0.1 1 10

Efficiency-%

I -LoadCurrent- A

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V =5V

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V =12V

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V =18V

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V =24V

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V =28V

I

PH

VIN

GND

BOOT

VSENSE

COMP

SS

C

SS

D1

VIN

VOUT

EN

TPS54331

C

I

C

BOOT

L

O

C

O

Ren1

R

O2

C

1

C

2

R

3

Ren2

R

O1

TPS54331

www.ti.com

....................................................................................................................................................................................................... SLVS839 – JULY 2008

3A, 28V INPUT, STEP DOWN SWIFT™ DC/DC CONVERTER WITH Eco-mode™

1

FEATURES

2

• 3.5V to 28V Input Voltage Range

• Adjustable Output Voltage Down to 0.8V

• Integrated 80 m Ω High Side MOSFET Supports

up to 3A Continuous Output Current

• High Efficiency at Light Loads with a Pulse

Skipping Eco-mode™

• Fixed 570kHz Switching Frequency

• Typical 1 µ A Shutdown Quiescent Current

• Adjustable Slow Start Limits Inrush Currents

• Programmable UVLO Threshold

• Overvoltage Transient Protection

• Cycle by Cycle Current Limit, Frequency Fold

Back and Thermal Shutdown Protection

• Available in Easy-to-Use SOIC8 Package

• Supported by SwitcherPro™ Software Tool

(http://focus.ti.com/docs/toolsw/folders/print/s

witcherpro.html )

• For SWIFT™ Documentation, See the TI

Website at www.ti.com/swift

DESCRIPTION

The TPS54331 is a 28-V, 3-A non-synchronous buck converter that integrates a low Rds(on) high side MOSFET. To increase efficiency at light loads, a pulse skipping Eco-mode™ feature is automatically activated. Furthermore, the 1 µ A shutdown supply current allows the device to be used in battery powered applications. Current mode control with internal slope compensation simplifies the external compensation calculations and reduces component count while allowing the use of ceramic output capacitors. A resistor divider programs the hysterisis of the input under-voltage lockout. An overvoltage transient protection circuit limits voltage overshoots during startup and transient conditions. A cycle by cycle current limit scheme, frequency fold back and thermal shutdown protect the device and the load in the event of an overload condition. The TPS54331 is available in an 8-pin SOIC package that has been internally optimized to improve thermal performance.

APPLICATIONS

• Consumer Applications such as Set-Top

Boxes, CPE Equipment, LCD Displays, Peripherals, and Battery Chargers

• Industrial and Car Audio Power Supplies

• 5V, 12V and 24V Distributed Power Systems

1

2 SWIFT, Eco-mode, SwitcherPro are trademarks of Texas Instruments.

PRODUCTION DATA information is current as of publication date. Products conform to specifications per the terms of the Texas Instruments standard warranty. Production processing does not necessarily include testing of all parameters.

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.

SIMPLIFIED SCHEMATIC EFFICIENCY

TPS54331

SLVS839 – JULY 2008 .......................................................................................................................................................................................................

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

T

J

– 40 ° C to 150 ° C 8 pin SOIC 570 kHz TPS54331D

(1) For the most current package and ordering information, see the Package Option Addendum at the end of this document, or see the TI

web site at www.ti.com.

(2) The D package is also available taped and reeled. Add an R suffix to the device type (i.e., TPS54331DR). See applications section of

data sheet for layout information.

ABSOLUTE MAXIMUM RATINGS

PACKAGE SWITCHING FREQUENCY PART NUMBER

(1)

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(2)

over operating free-air temperature range (unless otherwise noted)

VALUE UNIT

VIN – 0.3 to 30 EN – 0.3 to 5

Input Voltage V

Output Voltage PH – 0.6 to 30 V

Source Current

Sink Current COMP 100

Electrostatic Discharge (HBM) 2 kV Electrostatic Discharge (CDM) 500 V Operating Junction Temperature – 40 to 150 ° C Storage Temperature – 65 to 150 ° C

(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 reliabiltiy.

BOOT 38 VSENSE – 0.3 to 3 COMP – 0.3 to 3 SS – 0.3 to 3 BOOT-PH 8

PH (10 ns transient from ground to negtive peak) – 5 EN 100 µ A BOOT 100 mA VSENSE 10 µ A PH 9 A VIN 9 A

SS 200

µ A

PACKAGE DISSIPATION RATINGS

PACKAGE THERMAL IMPEDANCE JUNCTION TO PSEUDO THERMAL IMPEDANCE JUNCTION TO

SOIC8 100 ° C/W 5 ° C/W

(1) Maximum power dissipation may be limited by overcurrent protection (2) Power rating at a specific ambient temperature TAshould be determined with a junction temperature of 150 ° C. This is the point where

distortion starts to substantially increase. Thermal management of the PCB should strive to keep the junction temperature at or below 150 ° C for best performance and long-term reliability. See power dissipation estimate in application section of this data sheet for more information.

(3) Test board conditions:

a. 2 inches x 1.5 inches, 2 layers, thickness: 0.062 inch b. 2-ounce copper traces located on the top and bottom of the PCB c. 6 thermal vias located under the device package

(1) (2) (3)

AMBIENT TOP

Product Folder Link(s): TPS54331

TPS54331

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....................................................................................................................................................................................................... SLVS839 – JULY 2008

RECOMMENDED OPERATING CONDITIONS

over operating free-air temperature range (unless otherwise noted)

MIN TYP MAX UNIT

Operating Input Voltage on (VIN pin) 3.5 28 V Operating junction temperature, T

J

– 40 150 ° C

ELECTRICAL CHARACTERISTICS

TJ= – 40 ° C to 150 ° C, VIN = 3.5V to 28V (unless otherwise noted)

DESCRIPTION TEST CONDITIONS MIN TYP MAX UNIT SUPPLY VOLTAGE (VIN PIN)

Internal undervoltage lockout threshold Rising and Falling 3.5 V Shutdown supply current EN = 0V, VIN = 12V, 25 ° C 1 10 µ A Operating – non switching supply current VSENSE = 0.85 V 110 190 µ A

ENABLE AND UVLO (EN PIN)

Enable threshold Rising and Falling 1.25 1.35 V Input current Enable threshold – 50 mV 1 µ A Input current Enable threshold + 50 mV 4 µ A

VOLTAGE REFERENCE

Voltage reference 0.772 0.8 0.828 V

HIGH-SIDE MOSFET

On resistance BOOT-PH = 3 V, VIN = 3.5 V 115 200 m Ω

BOOT-PH = 6 V, VIN = 12 V 80 150

ERROR AMPLIFIER

Error amplifier transconductance (gm) – 2 µ A < ICOMP < 2 µ A, V(COMP) = 1 V 92 µ mhos Error amplifier DC gain Error amplifier unity gain bandwidth Error amplifier source/sink current V(COMP) = 1.0 V, 100 mV overdrive ± 7 µ A Switch current to COMP transconductance VIN = 12 V 12 A/V

SWITCHING FREQUENCY

TPS54331 Switching Frequency VIN = 12V 400 570 740 kHz Minimum controllable on time Measured at 90% to 90% of VIN, VIN = 12V 110 160 ns Maximum controllable duty ratio

PULSE SKIPPING ECO-MODE™

Pulse skipping Eco-mode™ switch current threshold 160 mA

CURRENT LIMIT

Current limit threshold VIN = 12 V 3.5 5.8 A

THERMAL SHUTDOWN

Thermal Shutdown 165 ° C

SLOW START (SS PIN)

Charge current V(SS) = 0.4 V 2 µ A SS to VSENSE matching V(SS) = 0.4 V 10 mV

(1) Specified by design

(1)

VSENSE = 0.8 V 800 V/V 5 pF capacitance from COMP to GND pins 2.7 MHz

BOOT-PH = 6 V 90 93 %

Product Folder Link(s): TPS54331

1

2

3

4

5

6

7

8

BOOT

VIN

EN

SS

PH

GND

COMP

VSENSE

TPS54331

SLVS839 – JULY 2008 .......................................................................................................................................................................................................

DEVICE INFORMATION

PIN ASSIGNMENTS

TERMINAL FUNCTIONS

TERMINAL DESCRIPTION

NAME NO.

BOOT 1 A 0.1 µ F bootstrap capacitor is required between BOOT and PH. If the voltage on this capacitor falls below the

minimum requirement, the high-side MOSFET is forced to switch off until the capacitor is refreshed. VIN 2 Input supply voltage, 3.5 V to 28 V. EN 3 Enable pin. Pull below 1.25V to disable. Float to enable. Programming the input undervoltage lockout with two

resistors is recommended. SS 4 Slow start pin. An external capacitor connected to this pin sets the output rise time. VSENSE 5 Inverting node of the gm error amplifier. COMP 6 Error amplifier output, and input to the PWM comparator. Connect frequency compensation components to this pin. GND 7 Ground. PH 8 The source of the internal high-side power MOSFET.

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Product Folder Link(s): TPS54331

Error

Amplifier

RQ

S

Boot

Charge

Boot

UVLO

Current

Sense

Oscillator

Frequency

Shift

Gate Drive Logic

Slope

Compensation

PWM Latch

PWM

Comparator

ECO-MODE

MinimumClamp

™

Maximum

Clamp

Voltage

Reference

Discharge

Logic

VSENSE

COMP

PH

BOOT

VIN

GND

Thermal

Shutdown

EN

Enable

Comparator

Shutdown

Logic

Shutdown

Enable

Threshold

S

1.25V

0.8V

80mW

165C

2.1V 12 A/V

SS

Shutdown

VSENSE

1 Am

3 Am

gm=92 A/V

DCgain=800V/V

BW=2.7MHz

m

2kW

2 Am

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110

-50 -25 0 25 50 75 100 125 150

T -JunctionTemperature-°C

J

Rdson-OnResistance-mW

VIN=12V

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1

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V -InputVoltage-V

I

Isd-ShutdownCurrent-

Am

EN=0V

T =150°C

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T =25°C

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T =-40°C

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550

555

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565

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-50 -25 0 25 50 75 100 125 150

fsw-OscillatorFrequency-kHz

T -JunctionTemperature-°C

J

VIN=12V

TPS54331

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....................................................................................................................................................................................................... SLVS839 – JULY 2008

FUNCTIONAL BLOCK DIAGRAM

CHARACTERIZATION CURVES

ON RESISTANCE SHUTDOWN QUIESCENT CURRENT SWITCHING FREQUENCY

JUNCTION TEMPERATURE INPUT VOLTAGE JUNCTION TEMPERATURE

Figure 1. Figure 2. Figure 3.

TYPICAL CHARACTERISTICS

vs vs vs

Product Folder Link(s): TPS54331

0.7760

0.7820

0.7880

0.7940

0.8000

0.8060

0.8120

0.8180

0.8240

-50 -25 0 25 50 75 100 125 150

Vref-VoltageReference-V

T -JunctionTemperature-°C

J

5.50

5.75

6

6.25

6.50

6.75

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7.50

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MinimumControllableDutyRatio-%

T -JunctionTemperature-°C

J

VIN=12V

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130

140

-50 -25 0 25 50 75 100 125 150

Tonmin-MinimumControllableOnTime-ns

T -JunctionTemperature-°C

J

VIN=12V

1.90

2

2.10

-50 -25 0 25 50 75 100 125 150

I

-SlowStartChargeCurrent- A

SS

m

T -JunctionTemperature-°C

J

3

4

5

6

3 8 13 18 23 28

V -InputVoltage-V

I

CurrentLimitThreshold-

A

T =150°C

J

T =25°C

J

T =-40°C

J

3 8 13 18 23 28

0.5

0.75

1

1.25

1.5

1.75

V

-OutputVoltage-V

O

V -InputVolatage-V

I

I =2 A

O

I =3 A

O

3 8 13 18 23 28

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5

10

15

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30

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V -InputVoltage-V

I

25

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150

0 0.2 0.4 0.6 0.8 1 1.2

P -PowerDissipation-W

D

T -JunctionTemperature-°C

J

TPS54331

SLVS839 – JULY 2008 .......................................................................................................................................................................................................

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TYPICAL CHARACTERISTICS (continued)

VOLTAGE REFERENCE TIME RATIO

vs vs vs

JUNCTION TEMPERATURE JUNCTION TEMPERATURE JUNCTION TEMPERATURE

Figure 4. Figure 5. Figure 6.

SS CHARGE CURRENT CURRENT LIMIT THRESHOLD

JUNCTION TEMPERATURE INPUT VOLTAGE

MINIMUM CONTROLLABLE ON MINIMUM CONTROLLABLE DUTY

vs vs

SUPPLEMENTAL APPLICATION CURVES

TYPICAL MINIMUM OUTPUT TYPICAL MAXIMUM OUTPUT

VOLTAGE VOLTAGE MAXIMUM POWER DISSIPATION

INPUT VOLTAGE INPUT VOLTAGE JUNCTION TEMPERATURE

Figure 9. Figure 10. Figure 11.

Figure 7. Figure 8.

vs vs vs

Product Folder Link(s): TPS54331

TPS54331

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....................................................................................................................................................................................................... SLVS839 – JULY 2008

TYPICAL CHARACTERISTICS (continued)

OVERVIEW

The TPS54331 is a 28-V, 3-A, step-down (buck) converter with an integrated high-side n-channel MOSFET. To improve performance during line and load transients, the device implements a constant frequency, current mode control which reduces output capacitance and simplifies external frequency compensation design. The TPS54331 has a pre-set switching frequency of 570kHz.

The TPS54331 needs a minimum input voltage of 3.5V to operate normally. The EN pin has an internal pull-up current source that can be used to adjust the input voltage under-voltage lockout (UVLO) with two external resistors. In addition, the pull-up current provides a default condition when the EN pin is floating for the device to operate. The operating current is 110 µ A typically when not switching and under no load. When the device is disabled, the supply current is 1 µ A typically.

The integrated 80 m Ω high-side MOSFET allows for high efficiency power supply designs with continuous output currents up to 3A.

The TPS54331 reduces the external component count by integrating the boot recharge diode. The bias voltage for the integrated high-side MOSFET is supplied by an external capacitor on the BOOT to PH pin. The boot capacitor voltage is monitored by an UVLO circuit and will turn the high-side MOSFET off when the voltage falls below a preset threshold of 2.1V typically. The output voltage can be stepped down to as low as the reference voltage.

By adding an external capacitor, the slow start time of the TPS54331 can be adjustable which enables flexible output filter selection.

To improve the efficiency at light load conditions, the TPS54331 enters a special pulse skipping Eco-mode when the peak inductor current drops below 160mA typically.

The frequency foldback reduces the switching frequency during startup and over current conditions to help control the inductor current. The thermal shut down gives the additional protection under fault conditions.

TM

DETAILED DESCRIPTION

FIXED FREQUENCY PWM CONTROL

The TPS54331 uses a fixed frequency, peak current mode control. The internal switching frequency of the TPS54331 is fixed at 570kHz.

ECO-MODE

The TPS54331 is designed to operate in pulse skipping Eco-mode efficiency. When the peak inductor current is lower than 160 mA typically, the COMP pin voltage falls to 0.5V typically and the device enters Eco-mode clamped at 0.5V internally which prevents the high side integrated MOSFET from switching. The peak inductor current must rise above 160mA for the COMP pin voltage to rise above 0.5V and exit Eco-mode integrated current comparator catches the peak inductor current only, the average load current entering Eco-mode

TM

. When the device is in Eco-mode

TM

varies with the applications and external output filters.

TM

at light load currents to boost light load

TM

, the COMP pin voltage is

TM

. Since the

VOLTAGE REFERENCE (Vref)

The voltage reference system produces a ± 2% initial accuracy voltage reference ( ± 3.5% over temperature) by scaling the output of a temperature stable bandgap circuit. The typical voltage reference is designed at 0.8V.

BOOTSTRAP VOLTAGE (BOOT)

The TPS54331 has an integrated boot regulator and requires a 0.1 µ F ceramic capacitor between the BOOT and PH pin to provide the gate drive voltage for the high-side MOSFET. A ceramic capacitor with an X7R or X5R grade dielectric is recommended because of the stable characteristics over temperature and voltage. To improve drop out, the TPS54331 is designed to operate at 100% duty cycle as long as the BOOT to PH pin voltage is greater than 2.1V typically.

Product Folder Link(s): TPS54331

EN

1.25V

VIN

+

-

Ren1

Ren2

TPS54331

1 Am 3 Am

START STOP

V - V

Ren1 =

3 Am

EN

START EN

V

Ren2 =

V - V

+ 1 A

Ren1

m

( )

( ) ( )

( )

SS ref

SS

C nF V V

T ms =

I A´m

TPS54331

SLVS839 – JULY 2008 .......................................................................................................................................................................................................

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ENABLE AND ADJUSTABLE INPUT UNDER-VOLTAGE LOCKOUT (VIN UVLO)

The EN pin has an internal pull-up current source that provides the default condition of the TPS54331 operating when the EN pin floats.

The TPS54331 is disabled when the VIN pin voltage falls below internal VIN UVLO threshold. It is recommended to use an external VIN UVLO to add hysterisis unless VIN is greater than (VOUT + 2V). To adjust the VIN UVLO with hysterisis, use the external circuitry connected to the EN pin as shown in Figure 12 . Once the EN pin voltage exceeds 1.25V, an additional 3 µ A of hysteresis is added. Use Equation 1 and Equation 2 to calculate the resistor values needed for the desired VIN UVLO threshold voltages. The V voltage, the V V

should always be greater than 3.5V.

STOP

is the input stop threshold voltage and the V

STOP

is the enable threshold voltage of 1.25V. The

EN

Figure 12. Adjustable Input Under-Voltage Lockout

START

is the input start threshold

PROGRAMMABLE SLOW START USING SS PIN

It is highly recommended to program the slow start time externally because no slow start time is implemented internally. The TPS54331 effectively uses the lower voltage of the internal voltage reference or the SS pin voltage as the power supply ’ s reference voltage fed into the error amplifier and will regulate the output accordingly. A capacitor (Css) on the SS pin to ground implements a slow start time. The TPS54331 has an internal pull-up current source of 2 µ A that charges the external slow start capacitor. The equation for the slow start time (10% to 90%) is shown in Equation 3 . The Vref is 0.8V and the Iss current is 2 µ A.

The slow start time should be set between 1ms to 10ms to ensure good start-up behavior. The slow start capacitor should be no more than 27nF.

If during normal operation, the input voltage drops below the VIN UVLO threshold, or the EN pin is pulled below

1.25V, or a thermal shutdown event occurs, the TPS54331 stops switching.

ERROR AMPLIFIER

The TPS54331 has a transconductance amplifier for the error amplifier. The error amplifier compares the VSENSE voltage to the internal effective voltage reference presented at the input of the error amplifier. The transconductance of the error amplifier is 92 µ A/V during normal operation. Frequency compensation components are connected between the COMP pin and ground.

SLOPE COMPENSATION

In order to prevent the sub-harmonic oscillations when operating the device at duty cycles greater than 50%, the TPS54331 adds a built-in slope compensation which is a compensating ramp to the switch current signal.

Product Folder Link(s): TPS54331

(1)

(2)

(3)

Texas Instruments TPS54331D, TPS54331 Datasheet

Specifications and Main Features

Frequently Asked Questions

User Manual

FEATURES

DESCRIPTION

APPLICATIONS

ABSOLUTE MAXIMUM RATINGS

PACKAGE DISSIPATION RATINGS

RECOMMENDED OPERATING CONDITIONS

ELECTRICAL CHARACTERISTICS

DEVICE INFORMATION

PIN ASSIGNMENTS

CHARACTERIZATION CURVES

TYPICAL CHARACTERISTICS

SUPPLEMENTAL APPLICATION CURVES

OVERVIEW

DETAILED DESCRIPTION

FIXED FREQUENCY PWM CONTROL

VOLTAGE REFERENCE (Vref)

BOOTSTRAP VOLTAGE (BOOT)

ENABLE AND ADJUSTABLE INPUT UNDER-VOLTAGE LOCKOUT (VIN UVLO)

PROGRAMMABLE SLOW START USING SS PIN

ERROR AMPLIFIER

SLOPE COMPENSATION