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LM293: PCN issue for LM293P

Harry Ma
Intellectual 2945 points

Part Number: LM293
Other Parts Discussed in Thread: LM339

Tool/software:

HI Team

Customer found the device of pre-PCN and post-pcn performs different in their system, I summarize it as following attachment. Can you help to explain why?

LM293P PCN Issue.pptx

  • 0
    TI__Guru 70376 points

    Hello Harry,

    Remove C47. Any capacitance on the positive node will negate the hysteresis and can cause "bursting"  - similar to what I see in the photos.

    The post PCN device is faster and is more responsive.

    These devices do NOT like negative voltages. Please see section 6.9.2 of the LM339 application note:

    Application Design Guidelines for LM339, LM393, TL331 Family Comparators

    What are the date codes of the failing devices? I'm assuming these are Ji3 devices (CCO:CHN).

    The newer TiB devices handle negative voltages better. TI really recommends that they add external negative clamping as mentioned in the appnote.