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LM3643: Increasing start up timing and response

Jeff Coletti
Expert 8695 points
Part Number: LM3643

Hi Support team

Customer has the following question, I also have a power point i can  share via email

We would like to significantly speed up this white LED current response time. Perhaps there is a way? Are there any top secret registers that can help for example?

 

Can you ask your team?  Our ASIC gets there in ~15usec, so this would be a nice target.

 

Does the LED current profile look right? Note the voltage across the 0.1 Ohm resistor follows the LED current. The profile shows a fast step up followed by a slower rise to the steady state level with some overshoot- not all that pretty.  I think it is related to the boost turning on. We use IR mode.

 

Thanks, Jeff Coletti

  • 0
    TI__Mastermind 22745 points

    Hi Jeff,

        Yes, our LM3643 can speed up the current response under IR and Pass mode, but 15us is too challenging.

        Here is the LM3643 current response under 1.5A output, IR mode and Pass mode: The typical response is about 35us.

         

        Here is the LM3643 current response under 1.5A, IR mode and Boost mode: The typical response is about 200us.

        

        And some of our customers has used this for facial recognization with this device, that's very popular. So what's your customer's detail application? Why they need those so fast response time? Thanks.

    Best Regards

    Sean