TS4274

5V/400mA Fixed Voltage

Ultra Low Dropout Voltage Regulator

4/6

Version: B13

Application Information (Continue)

Thermal Characteristics

A heatsink may be required depending on the maximum power dissipation and maximum ambient temperature of

the application. Under all possible operating conditions, the junction temperature must be within the range specified

must be calculated.

IIN = IL / IG

= 400mW + 36mW

= 436mW

The next parameter which must be calculated is the maximum allowable temperature rise.

TR(max) is calculated by the using to formula:

TR(max) = TJ(max) – TA(max)

Where: TJ(max) is the maximum allowable junction temperature, which is 125

Using the calculated values for TR(max) and PD, the maximum allowable value for the junction to ambient thermal

θ

IMPORTANT: if the maximum allowable value for is found to be ≥60

the TO-263 package, ≥150

needed since the package alone will dissipate enough heat to satisfy these requirements. If the calculated value for

θ

DPAK Thermal Resistance and Maximum Power Dissipation vs. P.C.B Copper Length