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TPS62867: Vout and PG when Vin < 1.8V

Ning LU
Prodigy 70 points
Part Number: TPS62867
Other Parts Discussed in Thread: TPS566231,

Hello,

I would like to confirm what would be the value of Vout, when 

1) Vin < 1.8V (for example, Vin = 1.1V)

2) EN is low.

I am expecting Vout = 0 V.

Is it correct?

And, according to Table 8-1 in datasheet, PG behavior under Vin 1.8V is not defined. 

What does it mean? If i connect PG to Vout throught a 100K resistor, is PG also = 0 V under this condition?

Thank you.

/Roland

  • 0
    TI__Guru*** 144450 points

    Hi Roland,

    Yes, if there is no Vin (and/or EN is low), the output of this IC is high impedance.  It does not transfer any energy to Vout, so leakage on the output should bring Vout down to 0V.

    Undefined means that it could be either high or low.  For PG, there is not enough Vin to hold the PG transistor ON so the PG pin should float (high).

    Thanks,

    Chris

  • 0 in reply to Chris Glaser
    Prodigy 70 points

    Hi Chris,

    I believe so when Vin = 0 V.

    However, will that also be the case when Vin is not exact 0, but still < 1.8V, for example, when Vin = 1.3V ? 

    I ask because since my ordered 62867EVM not arrived yet, so i tested on another IC TPS566231, it seems not exactly the case.

    For some reason, there is 1.6V voltage on Vin of TPS566231 (from leakage of a schottky diode), and i can see about 1.3V on output (EN floating). So i am not sure if 62867 would be the same behavior.

    /Roland

  • 0 in reply to Ning LU
    TI__Guru*** 144450 points

    Hi Roland,

    It sounds like you have a question about a specific TPS566231 circuit.  Please make a new thread for assistance with that device.

    The TPS62867 will output 0V, if Vin is below UVLO.

    Chris

  • 0 in reply to Chris Glaser
    Prodigy 70 points

    Chris,

    thanks for the confirmation. 

    I am not trying to ask question about TPS566231 but want to confirm the behavior on 62867.

    As you already confirmed the condition when Vin is less than UVLO but not absent, i think it is clear now.

    About PG, as you mentioned Vout will be bring down to 0 due to the leakage of output. Since the PG is connected to Vout through a resistor, can i expect PG will also be bring down to 0V?

    /Roland

  • +1 in reply to Ning LU
    TI__Guru*** 144450 points

    Yes since PG would be pulled up to Vout.  If Vout is 0V, PG will also be 0V.

    Some customers pull-up PG to Vin or another rail instead.  This would result in different behavior.

    Chris

  • 0 in reply to Chris Glaser
    Prodigy 70 points

    Thank you for the kind help. It answers my question.

    /Roland