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Original question:

TPS7A74: Maximum ROC of VIN

TPS7A74: Input Capacitor for IN and BIAS

Dice-K
Mastermind 7480 points
Part Number: TPS7A74

Hi support team,
This is a question when IN and BIAS are the same supply.

According to the datasheet, an input capacitor of 4.7μF or more is required, but do I need one for the IN pin and one for the BIAS pin?
Or do we cover both pins with a single 4.7uF?

I'm wondering because "Pin Functions" has a description on the BIAS pin and "ROC" has a description on the IN pin.

Regards,
Dice-K

  • TI__Genius 12511 points

    Hi Dice-K,

    This particular meaning is that a 4.7uF capacitor is sufficient for both the rails at the same time. That is to say only one 4.7uF capacitor is required. Because they are tied to the same rail, if 4.7uF or more is placed on that rail, close to the device, then you will be satisfying the recommended operating conditions for the device.

    Regards,

    John

  • in reply to John Schneider
    Mastermind 7480 points

    Hi John,
    Thank you for your reply.

    If covered by a single 4.7µF, IN and BIAS should be on the same island.

    In that case, is the best way to make the SS line the under layer?

    Best regards,
    Dice-K

  • in reply to Dice-K
    TI__Genius 12511 points

    Hi Dice-K,

    Yes, by utilizing a via and placing the ss functionality below the device, you would give yourself the ability to have a single plane pour for both VBIAS and VIN allowing for a solid connection for the Cbias/input capacitor on both rails. That is a clean way to satisfy those demands.

    Regards,

    John