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Soft-Start of TPS2560

user446310155
Intellectual 460 points
Other Parts Discussed in Thread: TPS2560

Hi Supporter,

Here is a question about TPS2560's soft-start that:

I'd like to tie the enable pins of TPS2560 to ground directly but I'm afraid of it will make the soft-start no function consequently too large inrush current causes the supplying system standby power drop during power up so system cannot bring up normally. 

So, two scenarios I just think of maybe you can tell me which one is close to TPS2560's behavior when the enable pins are tied to ground,

1. When power-up and the input voltage gets the minimum required level of the gate driver's charge pump, the voltage of output will just follows the input power to ramp-up therefore no soft-start.

2. the soft-start is put close to the output of gate driver so even though the enable pins are tied to ground the control of N-channel pass-gate is always works with soft-start.

Your kindly help will be appreciated.

Regards,

SP Lin@ADLINK

 

  • 0
    TI__Mastermind 42795 points

    The device will limit the inrush current into the IN pin during either case. Unfortunately, I don't have a representative waveform to send but will try to collect one today using the EVM.

  • 0 in reply to Eric Wright
    Intellectual 460 points

    Hi Eric,

    A waveform to demonstrate the soft-start is good.

    But I think you can show me where is the soft-start in TPS2560's block diagram so I can understand the reason why soft-start always works no matter the connection of TPS2560's enable pin.

    What do you think about?

    Regards,

    SP Lin@ADLINK

  • 0 in reply to user446310155
    TI__Mastermind 42795 points

    The "soft start" is really the current limit block in the block diagram. When VIN rises above the UVLO threshold of ~2.35V, TPS2560 initializes and then if EN is active OUTx will rise after ~3-4ms. If OUTx is shorted, then the current will rise up to the value programmed by the ILIM resistor.

    TPS2560 ramp up into overload (3ohm) with 550mA ILIM setting

    TPS2560 ramp up into 0.5 ohm load with 2.8A ILIM setpoint