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LM5170EVM-BIDIR: Onboard Voltage Control Testing

Part Number: LM5170EVM-BIDIR

Hi,

I'm testing the onboard voltage control. I'm facing a very weird issue. I configured the EVM in buck mode with jumpers according to the user guide. It was working and the D12 yellow LED was also lit. I measured 12.5V across the 12V port, while applying a voltage of about 24V on the 48V port.

I switched everything off and restarted the setup without changing anything, and now it doesn't work. D12 doesn't turn on, and there is no voltage on the 12V port. I literally did not change anything and the jumper setting and wire connections are exactly the same. It seems like the chip suddenly is not getting power. The jumper settings are shown in the picture below:

Is there something I'm missing and could you please help me if possible?

  • Hi,

    You might have damage the EVM again. What was your shutdown procedure? What did you do exactly to "switching everything off"?  Also, please reattach a photo with good resolution because I cannot tell whether a jumper cap is applied or not at some locations.

    Thanks,
    Youhao

  • Hi,

    In terms of shutdown procedure, I just turned off the power supply on the 48V port. That was the only source of power to the EVM. The photo is below:

    Also, I realized that I was not applying an external EN signal on J17, pin 5. I did that now, and it works fine again. This is also repeatable as I turned off the supply and did this test a couple of times and it still works. However, there are two concerns here:

    1. How did the board work for the first time as outlined above without the EN signal?

    2. When the EVM is providing the 14.5V output on the 12V port, I removed the EN signal to check if the EVM turns off. However, this does not happen and I continue to see the 14.5V output on the 12V port.

    Could you please comment on the above?

  • Hi,

    I think you need to actively pull down EN to disable the operation. 

    Thanks,

    Youhao

  • May I assume this issue is resolved so I can close the thread?  You are welcome to re-open it by adding a new post. 

    Good luck in your design.

    Thanks,

    Youhao