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MicroZed power, USB and backplane?

rdb98789

Hello, we have created a MicroZed carrier card that provides the 5V power source through the expansion connectors. However, we like to plug in the USB cable sometimes to see the serial printout. Some questions:

1) Is there any issue in having both supplies connected at once? So USB cable connected as well as the 5V regulator on our carrier card?

2) Is there any way to disable getting powered via USB? I'd like to test some power cycle reboot stuff while watching the USB UART data, but I need a true power cycle (including the carrier card components which is not powered by USB). Any recommendations?

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    I believe that Avnet always powers the USB to Uart chip from the USB cable.   That means you can power cycle the board without interrupting the serial connection.

    You must be powering the MicroZed from the carrier board by connecting 5V to the VIN_HDR pins.  VIN_HDR goes through a diode to make VIN which drives all the regulators.  The problem is that VBUS from the USB uart also goes through a diode (D4) to VIN.  If you turn off VIN_HDR the board will continue to run from the USB VBUS.

    I don't see a way to do what you want without removing D4.

    Please post your final decision.

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    I believe that Avnet always powers the USB to Uart chip from the USB cable.   That means you can power cycle the board without interrupting the serial connection.

    You must be powering the MicroZed from the carrier board by connecting 5V to the VIN_HDR pins.  VIN_HDR goes through a diode to make VIN which drives all the regulators.  The problem is that VBUS from the USB uart also goes through a diode (D4) to VIN.  If you turn off VIN_HDR the board will continue to run from the USB VBUS.

    I don't see a way to do what you want without removing D4.

    Please post your final decision.

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