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LM5050-1: LM5050-1 - Finding a leakage current from OFF pin to VS pin

GaryC
Expert 3295 points
Part Number: LM5050-1

We find a leakage from OFF pin to VS pin though by LM5050-1 at no load turn on,

The control circuit on OFF pin is a simple circuit, 3.3V pull high 10K with DSP signal to control it.

If I short control signal to ground, or series a diode on VS, then leakage will be solved.

this issue need to consult you and need your explain,

and one more question: If I put a diode on VS pin to prevent leakage, it will let Vout > VS-0.2V, Does it have any side effect?

BR,

Gary

with Leakage current

NO Leakage current.

Schematic:

-

  • 0 in reply to Praveen GD
    TI__Expert 3295 points

    One more question.

    The leakage still happen when connect VS pin to IN.

    But it will be pull low by internal discharge circuit.

    If I disable internal discharge circuit, then different of leakage voltage only have Vf of oringFET.

    This way can't solve the root of the problem, Just solve it by other circuit.

    Could you please help to explain,

    1. Why have a leakage path from OFF pin to VS pin? We can’t analysis from block diagram in datasheet.
    2. If modify VS pin connect from OUT to IN, it will have side effect?

    BR, Gary

  • 0 in reply to GaryC
    TI__Guru 57737 points

    Hi Gary,

    Please see my response below,

    1. We have checked this internally. Yes, there is leakage through the internal path (from OUT to VS) which we cannot reveal more here due to confidentiality of the internal circuit. If it is critical for customer, I would recommend you to reach out on email. This leakage should not be an issue as the voltage on the OUT is only around 1V which will not turn ON any downstream loads. 

    2. Yes, Customer can connect the VS pin to IN and no issues in terms of damage to components.

      However, if there are requirements to survive input micro-short conditions (short 100us interruptions) where LM5050 turns off quickly and then required to turn back on after the micro-short is removed, we can increase the capacitance on VS pin to hold Vs voltage so that LM5050 is powered and ready to turn back on quickly after input short. (By the way, I don't see cap on the VS pin. Please add this cap)

      If you don't have above requirements, then we don't see any issues.