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TS5A4624: Behavior when V+=0V

shinichi yumoto
Prodigy 40 points
Part Number: TS5A4624
Other Parts Discussed in Thread: TPS2051

Tool/software:

Used to switch the USB VBUS voltage monitor.

When the device is powered off (V+=VI=0V) and the NO terminal is connected to a PC USB,

VBUS (5V) appears on the NC and COM terminals, and about 3V appears on the V+ terminal.

Is this behavior expected?

Is there a workaround?

  • 0
    TI__Mastermind 35208 points

    Hi Shinichi,

    That doesn't sound like normal behavior. When the supply is 0V, this device should isolate the NC/NO and COM from each other. The fact that 3V shows up on V+ makes sense though why the isolation isn't there. Before we try and figure out why that may be happening, have you tried replacing the unit with a different new unit? It could be damage causing some back-powering.

    Thanks,
    Rami

  • 0 in reply to Rami Mooti1
    Prodigy 40 points

    Thank you for your reply, Rami.

    I haven't replaced any parts, but the operation is the same for all the boards I've made.

    I found out that there is a procedure.

    When 5V is applied to V+ and the PC VBUS is connected NO terminal, the operation is as expected,

    but if V+ is then set to 0V, the isolation becomes abnormal.

    Furthermore, if the USB connection is then turned OFF and then ON,

    the isolation becomes normal.

  • 0 in reply to shinichi yumoto
    TI__Mastermind 35208 points

    Hi Shinichi,

    Thanks for providing more information. I'm going to take a look at this myself and do some bench tests. However, I don't have the specific part on me so it'll take likely around a week to come in. In the meantime, I have some parts that are in its family that I'll play around with and see if I can replicate this.

    Can you also make it a bit more clear on what signals go where exactly for your tests so I can follow the same setup. I have a start but want to make sure we're on the same page before going to the lab

    Thanks,
    Rami

  • 0 in reply to Rami Mooti1
    Prodigy 40 points
    The NC terminal is the 5V inside the board for VBUS output. When a USB device is connected, the 5V inside the board is output via TPS2051. The NO terminal is connected to the VBUS of the USB host. V+ is the 5V inside the board.