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TPS2556 issue

Jim CHEN
Expert 4795 points
Other Parts Discussed in Thread: TPS2556

Hi Sir,

My customer met a output unstable issue as below:

CH1 is USB_PWR(5V)

CH2 is EN pin

They have 3 load on this path: Ethernet IC, USB HUB and Wifi IC.

GPIO of SoC (EN pin) could work normally if we cut off the connection.

The schematic as below:

It can work normally after remove the Ethernet IC as below:

The power-on peak current of Ethernet IC is about 300mA

They tried to remove all of three load and use facility to sink up to 3A. TPS2556 can work normally.

And changing a smaller value of ILIM resistor doesn't work for this issue.

Please help to give some comments.

Thank you.

  • 0
    TI__Mastermind 43875 points

    The time constant of the RC filter created by the 100K and 0.1uF capacitor is huge, in the order of 10ms.

    I think the values in the example in the datasheet are there to delay the enable until power is stable (i.e. enable is connected to the input power). Your use case is not the same and is controlled by an independent enable signal, so the filter/delay is not needed (actually, not desirable)

    Try reducing the resistor and/or capacitor significantly.

    BR,

    Steve

  • 0 in reply to Steve Clynes
    TI__Mastermind 43875 points
    On a side note, if you are trying to implement auto recovery then you need to connect 'fault' to the RC node I think.

    Try the simple case first (no fault recovery, no RC delay) to see if this is an over current issue or a control issue. Once you know what is causing the TPS to turn off you can then try to determine why.

    BR,
    Steve