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UCD90160A: Alert-LED is constantly on, when UCD90SEQ64EVM-650 is powered from external jack and not from USB

Part Number: UCD90160A
Other Parts Discussed in Thread: UCD90160, UCD90SEQ64EVM-650, , USB-TO-GPIO

Dear TI team,

when powering the EVM from USB the Alert-LED is only lighting up, when an Alert has been detected (assuming that the UCD device is not empty but loaded with a valid configuration, not asserting Alert). When then changing the power of the board from USB (unplug USB cable) to an external +5V source, the LED is permanently on.

Can anybody confirm that or is it just my board ?

Best regards


  • Are you using the TI UCD90160 EVM? This does not sound right. On the TI EVM,the alert pin will not affect by the power source, which is confirmed.
    Could you launch the GUI to see whether there is any status reported?
  • Hi,

    I am using the TI UCD90SEQ64EVM-650 EVM and currently have installed the UCD90160A device in it.

    Without wiring another adapter to it, I would not be able to work with the GUI, since the USB connector is unplugged at that point.

    Maybe it is just my board that is behaving weird ?!?

    Best regards
  • COuld you please confirm
    1. The only difference in your test is the power from USB cable or powerfrom external 5V(on J5).
    2. It is on the same UCD90160A device. this have the EVM schematics.

    you can jump wire the SCL/SDA from USB-to-GPIO dongle to the SCL/SDA pin on the EVM to get the communcation.


  • Hi Yihe,

    I just found the time to further test this on my EVM, with the USB-to-GPIO dongle connected to the EVM SDA/SCL pins.

    When I changed EVM over from USB power (no alert LED and no alert status in GUI) to 5V supply alert LED lights up red. Then I attached USB dongle and the status read back was "no alert". When I then issued either a soft reset or pressed the PB-reset button on the EVM the alert LED is cleared.

    When turning off/on my external 5V source, alert LED is again asserted, until a soft/hard reset.

    So maybe that is an issue with my power supply ?!?

    As the device is working on our own PCB design and also in the EVM with USB or external power (after additional reset) I think we can close this thread here.

    Best regards