ZXLD1322 datasheet(12/17 Pages) DIODES

12 / 17 page

ZXLD1322

Document number: DS32166 Rev. 3 - 2

12 of 17

www.diodes.com

April 2010

A Product Line of

Diodes Incorporated

The TADJ pin of the device has a voltage threshold of 75mV nominal, which is derived from the reference voltage VREF. If

the voltage (VTADJ) on the TADJ pin is held above the threshold, the thermal compensation current will be zero and no

thermal compensation is applied. However, if VTADJ falls below the threshold, a thermal compensation current (ITC) is

produced that is proportional to VTADJ. ITC is injected into the control loop in such a way as to reduce the demand current

IADJ, causing the control loop to decrease the LED current. The LED current will be reduced to less than 10% of the set

value when VTADJ falls below 50mV.

The threshold voltage has been chosen to set a nominal threshold of 105°C and the device has been optimized to operate

with a standard 103KT1608 thermistor and 5k resistor in the potential divider. Circuit details are given in the application

notes. Alternative thermistor/resistor networks can be used providing the input resistance presented to the device at the

TADJ pin is similar at the threshold temperature. If no LED thermal compensation is required, the TADJ pin should be

connected to VREF to disable this function.

ZXLD1322 Datasheet(PDF) 12 Page - Diodes Incorporated