ZHCSDK4C September 2014 – January 2020 TPS92638-Q1
PRODUCTION DATA.
This device operates a thermal shutdown (TSD) circuit as a protection from overheating. For continuous normal operation, the junction temperature should not exceed the thermal-shutdown trip point. If the junction temperature exceeds the thermal-shutdown trip point, the output turns off. When the junction temperature falls below the thermal-shutdown trip point minus hysteresis, the output turns on again.
Calculate the power dissipated by the device according to the following formula:
where:
nk = Number of LEDs for x channel
V(LEDk)= Voltage drop across one LED for x channel
V(REF) = Reference voltage, typically 1.24 V
I(LEDk) = Average LED current for channel k
After determining the power dissipated by the device, calculate the junction temperature from the ambient temperature and the device thermal impedance.
where:
TA = Ambient temperature
RθJA = Junction-to-ambient thermal impedance
P(IC) = Dissipated power