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LP5912: Can PG keep low before VIN reach 1.6V?

? ?
Prodigy 120 points
Part Number: LP5912

Hi ti,

   The PG is undefined when VIN is less than 1.6V, you may see on datasheet. You may also see such as fig 3. ,it shows the PG keep low during 0<VIN<1.6V. 

   Does such a "undefined" mean "can not be high impedance" ? 

  • 0
    TI__Genius 12511 points

    Hi,

    By undefined we are specifying that the device is neither in an active state of pulldown or pullup. So even if a state of voltage is applied to the output pin that PG would normally trip at, because it is not provided enough power, it will not work properly, it could be partially powered and trip at an earlier voltage, or not trip at all. It has the possibility to be high impedance, but it is not expected to be high impedance as it is not being properly powered.

    Regards,

    John

  • 0 in reply to John Schneider
    Prodigy 120 points

    Two LP5912s are used to convert 5V to 1.8V in my design. One's PG connect to the other's EN to complete dual 1.8V power up sequencing.

    Does LP5912 keeps output low regardless of EN during VIN<1.6V? Any track function between VIN and output?

    It seems that PG status is not sensitive to downstream LDO's EN when PG is pulled up to output low(no drive capability). 

  • +1 in reply to ? ?
    TI__Genius 12511 points

    This device does not have UVLO, so there is a likelihood that above around 1.3V the device begins to turn on if enabled, from figures 1-3 you can see that VOUT will begin tracking VIN once that threshold is crossed and the device is powered on. However PG will not be pulled high until VOUT gets all the way up to the PG threshold on a 1.8V setpoint. So below 1.6V you will not see PG trigger, even if VOUT begins to rise, below the 1.6V VIN.

    If disabled no tracking will occur and PG will hold low.

    Regards,
    John