TS2938CS datasheet(5/7 Pages) TSC

5 / 7 page

TS2938

500mA Ultra Low Dropout Voltage Regulator

with Inhibit Function

5/7

Version: A07

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

under absolute maximum ratings. To determine if the heatsink is required, the power dissipated by the regulator, PD

must be calculated.

The below formula shows the voltages and currents for calculating the PD in the regulator:

IIN = IL / IG

PD = (VIN-VOUT) * IL + (VIN) * IG

Ex. PD = (3.3V-2.5V) * 0.5A + 3.3V * 11mA

= 400mW + 36mW

= 436mW

The next parameter which must be calculated 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

oC for commercial grade parts. TA(max)

is the maximum ambient temperature which will be encountered in the application.

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

resistance, θJA, can now be found:

θJA = TR(max) / PD

Inhibit Input

TS2938 feature an active-low (Inhibit) input that allows ON/OFF control of the regulator. The Inhibit input has

TTL/CMOS compatible thresholds for simple interfacing with logic interfacing. Inhibit should be directly tied to

Ground or keep open (not connected).

TS2938CS 数据表(PDF) 5 Page - Taiwan Semiconductor Company, Ltd