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Random Failures in Latest Build

Category: Hardware
Product Number: ADM7171

We have been using the ADM7171 for couple of years now, all low volume runs <60 pcs per run, and have never had any issues.  On our most recent run we are now seeing, as far as we can tell, random failures of the ADM7150ACPZ-3.3.  We have six of these supplies per board and the failures are random within and between boards.  There is no systematic failure we have been able to identify and as mentioned we have been using this part with these components for a couple of years and have never once seen a failure.

All failures have been observed off of the assembly line.  Occasionally we have seen a failure after rework when using a part from the same batch, currently these parts are on order at all suppliers so we have not been able to purchase more.

The failure is generally been observed as an output voltage of ~1.3 V to 1.4 V instead of the fixed 3.3 V.

We have had a change in manufacturers on the most recent run switching to a vapor phase process instead of conventional reflow.  No other parts on the board have experienced failures, off of the assembly line.

The parts purchased this run were from a recommended distributer, Arrow.

Parents
  • Additional testing on our board, good LDO vs. bad LDO.

    Good LDO

    Note: Ven is 3.3 V here and Vin (5V) is not shown. Vin is the same 5V power rail for both the good and bad LDO.

    Channel 1 -> Ven (yellow)

    Channel 2 -> Vout (blue)

    Channel 3 -> Vref (red) 

    Channel 4 -> Vreg (green)

    Bad LDO

    Channel 1 -> Vin / Ven (yellow)

    Channel 2 -> Vout (blue)

    Channel 3 -> Vref (red) 

    Channel 4 -> Vreg (green)

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  • Additional testing on our board, good LDO vs. bad LDO.

    Good LDO

    Note: Ven is 3.3 V here and Vin (5V) is not shown. Vin is the same 5V power rail for both the good and bad LDO.

    Channel 1 -> Ven (yellow)

    Channel 2 -> Vout (blue)

    Channel 3 -> Vref (red) 

    Channel 4 -> Vreg (green)

    Bad LDO

    Channel 1 -> Vin / Ven (yellow)

    Channel 2 -> Vout (blue)

    Channel 3 -> Vref (red) 

    Channel 4 -> Vreg (green)

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