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LM25101 / Short pulse input

Kuramochi Tadahiko
Guru 28715 points
Other Parts Discussed in Thread: LM25101

Hi,

There is the following problem on the gate-driver of another vender.

The problem is that the High-side output doesn't fall when input pulse is narrow such as below.

The cause is filter by internal logic.

Does the LM25101have this problem, too?

Or does the LM25101have countermeasure for this problem?

Best Regards,

Kuramochi

  • 0
    TI__Intellectual 2910 points
    Thank you for considering LM25101 for your application. I am looking into your question. The LM25101 should not have this logic issue. Note that the device has a minimum pulse width spec (50ns typ) that must be met for the output to switch. Below this pulse width, the output will not switch.

    What minimum pulse width does the target application need to implement?

    - Daniel
  • 0 in reply to Daniel Ruiz
    Guru 28715 points
    Daniel-san,

    Thank you for your help.

    My customer is nervous for this problems.
    I wait result of your investigation.

    >Below this pulse width, the output will not switch.
    Does it mean that output doesn't go High when input pulse is narrow?

    >What minimum pulse width does the target application need to implement?
    My customer hope inputting 25ns min.

    Best Regards,
    Kuramochi
  • 0 in reply to Kuramochi Tadahiko
    TI__Intellectual 2910 points

    Yes, per the spec the output will not go HIGH if the input pulse is too narrow. This would prevent the behavior observed with the driver currently being used, whereby the output spuriously stays HIGH.

    Given the need for 25ns minimum pulse width, I will need a day or so to internally look into whether LM25101 or a different driver will fit the application better. 

    Feel free to provide other details, like which FETs are being driven, and voltage/current requirements.

  • 0 in reply to Daniel Ruiz
    Guru 28715 points

    Daniel-san,

    Thank you for your comment.

    I understand.

    My customer doesn't mind no to output when the input pulse is narrow.

    They does mind only that output stays HIGH.

    Please let me know when you get the result as soon as possible.

    Best Regards,

    Kuramochi

  • 0 in reply to Kuramochi Tadahiko
    TI__Intellectual 2910 points

    I got some samples of LM25101A and confirmed in the lab that the output will not stay HIGH when a short pulse (test conditions: 25ns) is applied at the HI input pin. The undesired behavior observed with the competitor part will not occur with the LM25101.

    In the oscilloscope screen captures below, Channel1/YELLOW is the HI input and Channel3/BLUE is the HO output.

    LM25101A_25ns.tif   LM25101A_25ns_multiple.tif

  • 0 in reply to Daniel Ruiz
    Guru 28715 points

    Daniel-san,

    Thank you for your great support!
    I'm glad to tell good result to my customer.

    Thanks and Regards,
    Kuramochi