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UCD90120A Does not start without PMBUS Cable

Kevin Roth
Prodigy 160 points
Other Parts Discussed in Thread: UCD90120A

Hello,

I have a UCD90120A in a design that originally seemed to work well. However, it now will not do anything at all unless I have the TI programming cable (USB-TO-GPIO) connected and the TI Fusion GUI launched. I have even loaded a simple project that only drives 1 IO pin low to light an LED. This will not happen until the TI Fusion tool connects to the device. Why could the UCD90120A get locked up without the GUI?

  • 0
    Prodigy 40 points

    Hi Kevin, just a thought.  There is a mode that requires the PMBus_CNTRL line to start a sequence.  I think there are three modes all told...OPERATION, PMBus_CNTRL, and I2C.  If the PMBus line is in the wrong state, it will stop things from happening.  This is only in the "Control" mode.  In the GUI, it's on the Vout CONFIG page/tab.  In the Rail Config Box, the pull down labeled "On/Off Config".

    Marcus 

  • 0 in reply to Marcus Perry
    Prodigy 160 points

    Hi Marcus,

    I have checked and the On/Off Config is set to 0x00 (None/Auto Enable). The Turn on Delay is 0.0ms and none of the Rail Seq On Dependencies or GPI Seq On Dependencies are checked. It appears that it should start right away every time.

    The only way I found to restore a device to a functioning state was to use the FusionFIrmwareDownload tool to completely clear program flash and then re-flash the chip with the firmware from a functioning board...

  • 0 in reply to Kevin Roth
    TI__Genius 9310 points

    It seems your device was boot in ROM mode (Program Flash checksum is zero). Thet is why the two options below work for you:

    1. Using Fusion GUI with the USB adapter will make it works because the Fusion GUI scans the device in both Normal Mode & ROM mode, if GUI detects the device is in ROM mode, will command the device to jump to Normal Mode by sending the SendByte command (0xF0) to address 11.

    2. Redownload the firmware (Program Flash)