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Original question:

LMC7211-N: Marking code LMC7211AIM5/NOPB

LMC7211-N: Marking Query

Steve Kynaston
Prodigy 20 points

Part Number: LMC7211-N
Other Parts Discussed in Thread: LMC7211

Hi

I have had some PCBs made to a deisgn I have had made several times before. I am getting different results with this latest batch which I have traced to a LMC7211AIM5X/NOPB part. When I replace the part with some old stock my circuit behaves as normal. The new parts have different top markings with three dashes above(1) and below(2) the C00A and have no date code on the bottom, all previous units which worked correctly and identically have simple top marking of C00A only and a date code on the bottom. It may just be a toleranceing issue, and I cannot believe a supply chain problem but can you confirm that top markings with dashes and no date code on the bottom is valid marking for this part?

  • 0
    TI__Guru 68126 points

    Hello Steve,

    There was a change in the die and the package markings.

    Product Change Notification (PDF)

    The "dashes" are a BCD datecode, and are consistent with the new die package. The new package does not have any markings on the bottom (if there are any, they may be  "tooling" ID markings from the mold).

    Can you share the details of the failure? The LOT# from the label or a photo of the markings?

  • 0
    Prodigy 20 points

    Hi Paul

    Thanks for the prompt reply.

    I use the device in a circuit which measures capacitance values of a sensor which vary between 100pF and 200pF. The circuit can also select fixed capacitors of 100pF, 150pF and 200pF for real time 'calibration'. Normally I see about 1-2% variation between units and between different batches. i.e the fixed 100pF readings may read 98-102pf. In this latest batch I am getting a fixed 30pF offset across multiple units i.e. my readings are 70-120 and 170. When I changed the LMC7211' device for one from old stock the readings reverted to what I have normally seen.    I would accept that my circuit is probably quite sensitive to the offset voltage variation and will start further investigations, but I am surprised I haven't seen such significant variation across previous batches.

    ...

    Not sure if the image has uploaded correctly.

    The C00A has a dash above the first '0', a dash below the 'C' and a dash below the second '0'.

    Date code and lot code from procurement is 2440  4126418HFT

    Cheers!

  • 0 in reply to Steve Kynaston
    TI__Guru 68126 points

    Hi Steve,

    The full lot code tells me exactly what it is...and is consistent with the dashes.

    It is the new PCN die, born on 10/14/2024.

    The new die does have a slightly different ESD structure, which may change input capacitance. The typical is 8pF CDIFF, which may be a bit more than the classic ESD diodes used on the original National LMC series (~2-3pF).

    Can you share the full or simplified schematic? I can contact you at your registered email address if you do not want to share the schematic publicly.