J(MAX)

A

D(MAX)

JA

T

T

P

-

=

q

1

VOUT

2

QOD

3

CT 4

ON

5

GND

6

VIN

VIA to Power Ground Plane

21

TPS22918

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SLVSD76C – FEBRUARY 2016 – REVISED JULY 2017

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11.2 Layout Example

Figure 32. Recommended Board Layout

11.3 Thermal Considerations

For best performance, all traces must be as short as possible. To be most effective, the input and output

capacitors must be placed close to the device to minimize the effects that parasitic trace inductances may have

on normal and short-circuit operation. Using wide traces for VIN, VOUT, and GND helps minimize the parasitic

electrical effects along with minimizing the case to ambient thermal impedance.

The maximum IC junction temperature should be restricted to 125°C under normal operating conditions. To

calculate the maximum allowable dissipation, PD(max) for a given output current and ambient temperature, use

Equation 14:

where

•

PD(MAX) = maximum allowable power dissipation

•

TJ(MAX) = maximum allowable junction temperature (125°C for the TPS22918)

•

TA = ambient temperature of the device

•

θJA = junction to air thermal impedance. Refer to the Thermal Information table. This parameter is highly

dependent upon board layout.

(14)