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TPS61196 UVLO fiter and IFB1...IFB6 resistors

Will Wang47
Expert 7750 points
Part Number: TPS61196

Dear All,

I have 2 questions about TPS61196.

First, I want to know the funtion of C4 and why connect C4 between R1 and R5.

Second, I want to know the function of R13-R18. What will happen if I don't connect those resisitors?

I hope you can help.

Kind regards.

  • 0
    TI__Expert 4550 points

    Hi Will,

    For your first question: the capacitor here is to eliminat the impact of the switching ripple and improve the noise immunity.

    And the 10M ohm resistor is meant to prevent IFBx pins are pulled up over limit. When one string is on and then turned off suddenly but other strings are still on. The Vout is still there, the current in this string drops down and Vf is also down. The IFB voltage is Vout-Vf, so IFB voltage will increase. But according to IV curve of LEDs, if you provide a few current such as 1uA, the Vf will increase a lot, the IFB voltage is down. To keep this current smaller enough and not to light up LEDs, large resistance is chosen . That’s why we recommend 10M ohm. Vout of TPS61196 could be really high, even over 100V, but the limit of IFB pins is only 40V.

  • 0 in reply to Caryss Li
    TI__Expert 7750 points
    Hi Caryss,

    Thanks for your reply. And I have understand the second question.

    But, for the first question, I want to know why don't connect C4 to UVLO pin? I think it's better if I want to filter for UVLO pin.

    Hoping for your reply.

    Thanks.

    Will
  • 0 in reply to Will Wang47
    TI__Expert 4550 points
    Hi Will,
    As you can see from datasheet, there is a current source inside of UVLO pin, a large capacitor here will effect the charging speed of UVLO. Instead , connect C4 between R5 and R1 could give a stable voltage and eliminate noise and no effect of current source function.