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LM5148: The 10uA current source mentioned below for the LM5148 turns OFF when the device enters Sleep mode

Kyohei
Expert 1440 points
Part Number: LM5148
Other Parts Discussed in Thread: LM5137, LM5149

Tool/software:

Hi team,

The 10uA current source mentioned below for the LM5148 turns OFF when the device enters Sleep mode, correct?

During the behavior in PFM mode, we have observed that under low load conditions, the device enters discontinuous mode, and the hysteresis of the EN signal does not function correctly.

We suspect that the cause might be the current source turning off when the device enters Sleep mode.

Best regards,

Kyohei

  • 0
    TI__Guru 73502 points

    Yes, the current source tuns off in sleep mode to save quiescent current.

  • 0 in reply to Timothy Hegarty
    Expert 1440 points

    Hi Hegarty,

    Thank you for your response.

    Is increasing the output current the only way to avoid sleep mode due to discontinuous mode?

    Best regards,

    Kyohei

  • 0 in reply to Kyohei
    TI__Guru 73502 points

    you could also run in FPWM...

  • 0 in reply to Timothy Hegarty
    Expert 1440 points

    Hi Hegarty,

    Thank you for your response.

    I understand that the 10uA constant current source turns off when entering sleep mode.

    When using PFM mode under low load conditions, the device will enter sleep mode due to discontinuous mode, and hysteresis will not be generated, so it will not function, right?

    My customer needs to maintain efficiency under low load conditions and cannot use FPWM mode or increase the output current.

    Is there an alternative device that can maintain efficiency under low load conditions while using the hysteresis function?

    Best regards,

    Kyohei

  • 0 in reply to Kyohei
    TI__Guru 73502 points

    Take a look at the LM5137. It has both voltage and current hysteresis on EN. Note, however, that it's a dual-channel controller, so it may be more than you need.

    Do you need 80V input capability? We also have a 42V device that's currently sampling and close to release.

  • 0 in reply to Timothy Hegarty
    Expert 1440 points

    Hi Hegarty,

    Thank you for your response.

    Thank you for the suggestion of LM5137.

    This device is only available as Q1 grade and is currently in Preview status, correct?

    Also, I checked the datasheet and the conditions for entering sleep mode are the same as LM5148 and LM5149, right?

    In that case, the 10uA constant current source is turned off and the hysteresis does not function even if RUV3 is used, I think.

    Also, I am currently using 48V input. Are there any alternative devices under the above conditions?

    Best regards,

    Kyohei

  • 0 in reply to Kyohei
    TI__Guru 73502 points

    Note that the LM5137 has an EN voltage hysteresis of 50mV. The device family will be released later this month.