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LM5122: “Cycle-by-Cycle Current Limit” always work regardless of operation mode?

Kazuhiko Hirano
Genius 14978 points
Part Number: LM5122

Hello,

Even LM5122 is under the bypass operation described in 7.3.9 of the datasheet, does the “Cycle-by-Cycle Current Limit” described in 7.3.10 still work? Or it works only during boost mode?

Best regards,

K.Hirano

  • 0
    TI__Mastermind 29990 points

    Hi Kazuhiko,

    Thanks for using the e2e forum.

    The cycle-by-cycle current limit only affect the low side gate driver (LO).
    In bypass mode, LO is turned off anyway, as the device is not boosting. Therefore triggering the current limit in bypass mode should have no impact on the behavior.
    The high side FET is not affected.

    Best regards,
    Niklas

  • 0 in reply to Niklas Schwarz
    TI__Genius 14978 points

    Niklas,

    Thank you for your response.
    So, the current limit does not work at all during the bypass mode?

    Best regards,

    K.Hirano

  • +1 in reply to Kazuhiko Hirano
    TI__Mastermind 29990 points

    Hi Kazuhiko,

    There is no note that the current limit is inactive during bypass mode.
    As mentioned before, both bypass mode and OCP are turning off the LO gate, so if device is already in bypass mode, OCP will become irrelevant.

    OCP only becomes relevant again, if Vout is dropping and the device should start switching again. Bypass mode is terminated, so the effects of OCP trigger will become visible again.

    Best regards,
    Niklas