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LTC3889 VIN over-voltage fault issue

Hi,

I'm testing a custom board with the LTC3889 and I cannot set the outputs to any voltage. The design is the same that 2595A Demo Circuit except for EXTVCC that in this case it's connected to an external 12V instead Vout0.

I've connected DC1613A to my board to check what's going on and here's what I see from LTPowerPlay:

  • VIN_OV_FAULT is present on STATUS_INPUT. Why? I power Vin with 48V
  • MFR_PADS is referred to LTC3886 instead LTC3889. Why? It is a LTpowerPlay bug?

Here's my LTC3889 package and attached schematic

PDF

Thanks in advance,
gaston



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[edited by: gschelotto at 11:23 AM (GMT -4) on 18 Mar 2022]
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  • Hi gaston,

    Apologies for delayed response. For the first question, the reason for VIN_OV_FAULT is that the VIN_OV_FAULT_LIMIT is set as 48V. When powering VIN with a voltage higher than 48V (even if slightly higher than 48V is sensed), VIN_OV_FAULT would be triggered. I would suggest to set VIN_OV_FAULT_LIMIT at about 55V since the max VIN for the demo board is 54V. It works just fine as when VIN=54V and the VOUT, FSW etc are at the default conditions of this demo board.

    For the second question, we can also see LTC3886 instead of LTC3889 in the LTPowerPlay when running the demo board. I think it may be a bug but definitely it will not impact the demo board operation.