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TPS796: startup behavior

Yuta Nishie
Genius 3440 points
Part Number: TPS796

I am considering replacing TPS79633 with TLV75733. I have a question about the startup behavior of each device. Could you please confirm the following?

■TPS79633

1) When the input voltage rises, the output voltage becomes the same as the input voltage. Is this correct operation of the TPS796?

2) If it is correct, could you tell me why this operation occurs based on the internal structure?

■TPS79633 vs TLV75733

1) The rise behavior of the two devices appears to be the same. Is this correct?

2) If it is correct, could you tell me why this operation occurs based on the internal structure? If it is not correct, could you tell me why this operation occurs based on the internal structure?

TPS79633.pdf

Best Regards,

NIshie

  • +1
    TI__Mastermind 43585 points

    Hi Nishie,

    If the input voltage ramp is slow enough, the output can catch up to the input and follow it until the output reaches the set point. This is true for all LDOs. This is exactly what is happening in the waveform you sent because the input rises very slowly (almost 30ms). If you want to see what the actual startup looks like for each device, speed up the input voltage ramp rate. It looks like you are simply turning on a DC bench supply; do you have a more controlled way to ramp the input?

    Regards,

    Nick

  • 0 in reply to Nick Butts
    Genius 3440 points

    Hi Nick-san,

    Thank you for your support.

    I understand that if the input rises slowly, it will have a waveform similar to the one in the attached document.

    I'm sorry. I don't have any equipment that can change the input lamp, so it's difficult to implement what you suggested.

    Best Regards,

    Nishie