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TPS2051: Connecting OC output of TPS2051 directly to EN input

Christoph Apel
Intellectual 540 points
Part Number: TPS2051
Other Parts Discussed in Thread: TPS2553

We designed a module with extremely limited pincount. TPS2051 interfaces to this module only via EN line, we don´t have additional line for OC (or VBUS).

TPS2051 controls the power of USB Type A socket.

To be able to sense overcurrent condition, we connected EN pin and OC pin together and use this signal in bi-directional configuration on our module: To enable the power, the module sets the line high-Z/input with pullup. If TPS2051 detects overcurrent condition and pulls the OC (and thus EN since connected together) low, our SW can sense this and keep EN low.

In this condition, our SW will change the line to high-Z/input every second to find out if the fault is still present.

We verified that the de-glitch circuitry on TPS2051 OC output works well and also our SW implementation works.

But naturally our SW is not able to overrule OC pin, we cannot do any additional de-glitching.

Please feedback if you consider this solution risky, e.g. when connecting bus-powered HDD.

thanks a lot and best regards,

Christoph

  • 0
    TI__Expert 8980 points
    Hi, Christoph,

    Can I reply you next week when I go back to office from CN holiday?

    Regards,
    Bob
  • 0
    TI__Expert 8980 points

    Hi, Chris,

    OC pin is an open-drain output. If OC pin is assert, this pin is connected to GND, so you can't overrule this pin. Can you overrule it when this part disabled? You should be able to overrule it when part is disabled if OC is high-z when disabled. One thing need to noticed that OC will asset again 8ms (deglitch time) after enable if overcurrent is not removed, so you just can overrule it for 8ms.

    If you want to overrule it when OC assert, maybe you can try to add resistor divider as pull up resistor. Connector EN between this two resistor.

    Below is auto-try circuit in TPS2553 datasheet FYI. To achieve this, fault need to be High-z when disabled. Obviously, TPS2553 is.

    Regards,
    Bob

  • 0 in reply to Bob Ma
    Intellectual 540 points
    Hi bob, thanks for that excellent reply. We tested using mechanical HDD and adding 100F on top and there is no trigger of OC when connecting this. So all is fine. best regards, Christoph
  • 0 in reply to Christoph Apel
    TI__Expert 8980 points
    That's great, glad to hear that.Thanks.

    Regards,
    Bob