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LM3429 CSH Pin

aarmutat
Intellectual 2590 points
Other Parts Discussed in Thread: LM3429

Referring to the CSH pin on the LM3429, I want to overdrive it with 2V or so (its rated to 6V ABS
MAX)to turn the LED drive off.  It looks like that will shut down the PWM
I just want to confirm that and that there won’t be any issues.

  • 0
    TI__Mastermind 43630 points

    Hi Andy,

    The biggest concern is the leakage into the CSH pin:

    Please look at how much current is sourced into this pin when over-driving it.

    A better way might be to simply drive nDIM to GND. When not in PWM mode, this is basically a UVLO pin. So grounding it should disabled the part.

    Let me know what you think.

    Regards,

  • 0 in reply to JCHK
    TI__Intellectual 2590 points

    Hi John,  Thanks for your reply.  nDIM operation is understood by the customer.  What series resistance is recommended if they are going to drive the CSH pin to 2V?

  • 0 in reply to aarmutat
    TI__Mastermind 43630 points

    Hi Andy,

    I will have to check with the design team. Their first question will likely be, 'Why do they want to do use the CSH pin instead of nDIM?'. I have the same question.

    Thanks,

  • 0 in reply to JCHK
    TI__Intellectual 2590 points

    Hi John,

    Tell them the same thing I'm going to tell you. It is a simple question. Know when to pick your battles and answer it. If you guys are truely intrigued with the application and design details, I will set up a call with the designer to review it in detail with you in detail... Provided you come prepared with some answers.

    Thanks, Andy