feedback
Rate this webpage

Need
Support?


Ask An Expert

Our Ask An Expert knowledge base contains answers to questions from designers like you. Browse the knowledge base by category or search key words. Not seeing what you need? Ask An Expert a question of your own.
All   >>  LED Lighting   >>   LCD Backlighting Applications   >>   Questions
 

Hi, our application needs to drive 2 different LED backlights (for 2 different LCDs). One of them has 2 LED strings and the other has 3 LED strings. Now my concerns are: 1. When we drive the LCD that has 2 strings, 2 other strings remain open and CAT4106 asserts the ;FAULT; signal indicating open LEDs on the un-used strings. I want to avoid this so that if an actual ;open LED; case occurs, the uC should know that. 2. When we drive the LCD that has 3 backlight strings, one remains open and the ;FAULT; signal gets asserted again indicating open LED string on un-used channel. I want to avoid this so that if an actual ;open LED; case occurs, the uC should know that.. Unfortunately, we need to implement this on the same platform without the BoM control (I mean the exactly same set of components should be able to handle both cases) One solution that I had in mind was to short LED3 ; LED 4 together to drive the 3rd string. However this doesn't solve the problem because in the case when the LCD with 2 strings in place, the ;FAULT; signal will be asserted again. Questions: 1. How can I design the circuit (supporting both LCDs with 2 ; 3 string LED confiigurations) without loosing the ;FAULT; feature in our application? 2. Is there any adverse impact of conecting a resistor of sufficient wattage in place of LED string.

The CAT4106 is a 4-channel LED driver. It is Not recommended to leave the LED channel open-circuit (unused). All channels should be connected LED strings. Answered by:
ON Semiconductor
2011-05-27 01:12:32.0