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TLV742P: Power MUX circuits

user6142633
Intellectual 440 points
Part Number: TLV742P
Other Parts Discussed in Thread: TPS22914

Hi, Team

I designed power mux circuits with TPS22914C and TLV742P like figure.

Circuits are operated as the following:
1. Enable TPS22914C and Vout rises to Vout_SW
2. Enable TLV742P.
3. Optionally, disable TPS22914C and Vout fall to Vout_LDO
There will be no reverse current from output to input of TLV742P because Vin_LDO > Vout_SW.

In measurement,
The output voltage rose slightly when TLV742P was enabled.

Why is output affected by Enable of LDO ?
Please give me your comment.

Best Regards,

Naoki

  • 0
    TI__Mastermind 44330 points

    Hi Naoki-san,

    One reason could be that the TLV742 has an active pull-down when disabled:

    Does VIN_SW exhibit the same behavior when the TLV742P is enabled?

    I hope this helps to clarify what could be happening.

  • 0 in reply to JCHK
    Intellectual 440 points

    Hi, John

    While TLV742P is disabled, output is Vout_SW. This is expected operation.

    When TLV742P become enabled, output rise slightly from Vout_SW.

    The exist of active pull-down cause the slight rise of output ?

    I don't know the reason why the ON/OFF of active pull-down cause the output voltage change.

    Best Regards,

    Naoki

  • 0 in reply to user6142633
    TI__Mastermind 44330 points

    HI Naoki-san,

    I am not sure what the output voltage is supposed to be but if it is 3.3V, when the TLV742P is disabled, it would be actively sinking ~27.5mA. Based on the RDSON of the TPS22914 (38mOhm), this alone would account for a ~1.9mV rise.

    What is the magnitude of the rise you are seeing?