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LM3478: LM3478

GOWRISANKAR THANNEERU
Prodigy 60 points
Part Number: LM3478

Hi,

I am using LM3478-IC  in  isolated flyback converter configuration. in this i have connected the compensation pin to a Zenar of 5V and the Opto-isolator. Please see attached document for your reference. 

I would like to know what is the maximum withstand voltage of Comp Pin of LM3478 IC. 

  • 0
    TI__Guru* 78200 points

    Hello,

    Thank you for considering the LM3478 in your design.

    The datasheet does not give the voltage rating because it is only intended to be an output pin not an input pin. Namely, it is not intended to feed a current into the pin. However, since you have 100K, this external pull up should not damage the IC.

    A more practical, and recommended, way is to delete the Zener and R154 completely. Unlike many other PWM controllers, the COMP of the LM3478 is the output of a Gm amplifier, or a current source. It will pull up the COMP pin by itself, not requiring R154.

    Thanks,
    Youhao Xi

  • 0
    TI__Mastermind 21720 points
    HI GOWRISANKAR,

    The COMP pin should not go above the COMP pin clamp voltage specified in the datasheet. This value is 2.4V.

    Thanks,

    Garrett