Any tendency to activate the thermal protection circuit indicates excessive power dissipation or an inadequate

heatsink. For reliable operation, junction temperature should be limited to 125°C maximum. To estimate the

margin of safety in a complete design (including heatsink), increase the ambient temperature until the thermal

protection is triggered; use worst-case loads and signal conditions. For good reliability, thermal protection should

trigger at least 35°C above the maximum expected ambient condition of your application. This produces a

worst-case junction temperature of 125°C at the highest expected ambient temperature and worst-case load.

The internal protection circuitry of the TPS731xx has been designed to protect against overload conditions.

It was not intended to replace proper heatsinking. Continuously running the TPS731xx into thermal shutdown

degrades device reliability.

7.4.1.2 Power Dissipation

The ability to remove heat from the die is different for each package type, presenting different considerations

in the PCB layout. The PCB area around the device that is free of other components moves the heat from the

device to the ambient air. Performance data for JEDEC boards are shown in the Thermal Information table.

Using heavier copper increases the effectiveness in removing heat from the device.

Power dissipation depends on input voltage and load conditions. Power dissipation (PD) is equal to the product

of the output current times the voltage drop across the output pass transistor (VIN to VOUT):

PD= VIN−VOUT ×IOUT

(6)

Power dissipation is minimized by using the lowest possible input voltage necessary to provide the required

output voltage.

7.4.2 Layout Examples

EN

VOUT

VIN

GND

PLANE

TPS731

C

OUT

GND

PLANE

R1

R2

C

IN

Figure 7-7. Example Layout for the Adjustable-Output Version (DBV Package)

GND

EN

VOUT

VIN

GND

1

2

3

5

4

CIN

COUT

CNR

Figure 7-8. Layout Example for the Fixed-Output Version (DBV Package)

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TPS731

SBVS034P – SEPTEMBER 2003 – REVISED APRIL 2026

Copyright © 2026 Texas Instruments Incorporated

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Product Folder Links: TPS731