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LM2678: LM2678SX-5.0/NOPBCT-ND

Shrishail Chikkamath
Prodigy 10 points
Part Number: LM2678


Tool/software:

Dear TI Support Team,
We recently ordered the LM2678SX-5.0/NOPBCT-ND component from Digi-Key (Order Number: 89501670). However, we are encountering an issue with the output voltage in this latest batch.
In our circuit, we are observing an output voltage in the range of 6V to 7V, instead of the expected 5V. We have attached the schematics of the circuit for your reference.
Notably, on the same PCB, we assembled an LM2678SX IC from a previous purchase, which is performing correctly with the expected 5V output. It appears that only the ICs from this new batch are experiencing the issue.
We have attached both the schematics and the order label for your reference. Could you please assist us in resolving this issue, or advise on any next steps we should take?
Thank you for your support.

  • 0
    TI__Mastermind 35210 points

    Hello,

    Sorry to hear about the issue.

    For the first batch of parts, how many boards were evaluated and appeared working? (X out Y working). Same question for the second batch.

    I don't have visibility on the particular parts you received just from the digikey order.

    Can you provide a picture of the label on the ESD bag/reel so I can have our team look up the lot?

    In addition, could you evaluate your design with a bad unit but make the following updates to the schematic to see if the behavior changes:

    1. Place 2 x 4.7uF, 50VDC MLCC capacitors on the input
    2. Change L1 to 22uH, >5ADC 
    3. Confirm ESR of output capacitor is 100mOhm or below and if not, change to a capacitor of same capacitance but ESR closer to 100mOhm.
  • 0 in reply to Marshall_Beck
    Prodigy 10 points

    Hi,
    In first batch of IC’s only two IC worked properly and others are same issue but in new batch non of the IC’s are working.
    And I have attached the IC package details.

     We have tested for your following input values but still no result found.

    Kindly help us to solve this issue ASAP

    .

  • 0 in reply to Shrishail Chikkamath
    TI__Mastermind 35210 points

    Thank you for the additional info,

    It doesn't seem that this is related to a specific lot of parts if in the first batch the majority of ICs malfunctioned.

    Can you provide waveforms demonstrating the device behavior with the updated component selection?

    Please include: VIN, ON, and VOUT. (pin1).

    In addition, I would like to also review the layout.

    I will work to get your issue resolved in a systematic and efficient way as possible.

    Sorry for the inconvenience thus far.