7.5.1.1 Board Layout Recommendations to Improve PSRR and Noise Performance

To improve AC measurements like PSRR, output noise, and transient response, TI recommends designing the

board with separate ground planes for VIN and VOUT, with each ground plane connected only at the GND pin of

the device. In addition, the ground connection for the bypass capacitor should connect directly to the GND pin of

the device.

7.5.1.2 Thermal Considerations

Thermal protection disables the output when the junction temperature rises to approximately 165°C, allowing

the device to cool. When the junction temperature cools to approximately 140°C, the output circuitry is again

enabled. Depending on power dissipation, thermal resistance, and ambient temperature, the thermal protection

circuit may cycle on and off. This cycling limits regulator dissipation, protecting the device from damage as a

result of overheating.

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

heatsink. For reliable operation, junction temperature must 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.

The TPS730 internal protection circuitry is designed to protect against overload conditions. This circuitry is

not intended to replace proper heatsinking. Continuously running the TPS730 into thermal shutdown degrades

device reliability.

7.5.1.3 Power Dissipation

Specified regulator operation is assured to a junction temperature of +125°C; the maximum junction temperature

should be restricted to +125°C under normal operating conditions. This restriction limits the power dissipation

the regulator can handle in any given application. To ensure the junction temperature is within acceptable limits,

calculate the maximum allowable dissipation, PD(max), and the actual dissipation, PD, which must be less than or

equal to PD(max).

The maximum power dissipation limit is determined using Equation 4:

J

A

D ( m a x )

J A

T m a x

T

P

R

4

(4)

where:

• TJmax is the maximum allowable junction temperature

• RθJA is the thermal resistance junction-to-ambient for the package (see the Thermal Information table)

• TA is the ambient temperature

The regulator dissipation is calculated using Equation 5:

D

IN

O U T

O U T

P

( V

V

)

I

u

(5)

Power dissipation resulting from quiescent current is negligible. Excessive power dissipation triggers the thermal

protection circuit.

Figure 7-7 illustrates the maximum ambient temperature versus the power dissipation of the TPS730. This figure

assumes the device is soldered on a JEDEC standard, high-K layout with no airflow over the board. Actual

board thermal impedances vary widely. If the application requires high power dissipation, having a thorough

understanding of the board temperature and thermal impedances is helpful to ensure the TPS730 does not

operate above a junction temperature of 125°C.

TPS730

SBVS054K – NOVEMBER 2004 – REVISED JUNE 2025

www.ti.com

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