TS2938_07 Datasheet, PDF (5/7 Pages) Taiwan Semiconductor Company, Ltd – 500mA Ultra Low Dropout Voltage Regulator with Inhibit Function

TS2938
500mA Ultra Low Dropout Voltage Regulator
with Inhibit Function
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, P_D
must be calculated.
The below formula shows the voltages and currents for calculating the P_D in the regulator:
I_IN = I_L / I_G
P_D = (V_IN-V_OUT) * I_L + (V_IN) * I_G
Ex. P_D = (3.3V-2.5V) * 0.5A + 3.3V * 11mA
= 400mW + 36mW
= 436mW
The next parameter which must be calculated the maximum allowable temperature rise.
T_R(max) is calculated by the using to formula:
T_R(max) = T_J(max) – T_A(max)
Where: T_J(max) is the maximum allowable junction temperature, which is 125^oC for commercial grade parts. T_A(max)
is the maximum ambient temperature which will be encountered in the application.
Using the calculated values for T_A(max) and P_D, the maximum allowable value for the junction to ambient thermal
resistance, θ_JA, can now be found:
θ_JA = T_R(max) / P_D
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).
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Version: A07