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LP3985: LP3985-Whether the 4pin carries current

user6350528
Expert 1210 points
Part Number: LP3985
LP3985IM5X-3.0/NOPB  The materials purchased before at the position of the 4th pin have no current, but the current we purchased this time has 1.2V. Please help to confirm whether this is normal and whether the materials behind will also carry current
  • 0
    TI__Genius 12511 points

    Hi,

    I'm confused as to whether you are talking current or voltage.

    The bypass pin should have a voltage present, but should not be creating any significant current, just a leakage through the bypass capacitor. Generally these are tied to a current source and is used to keep the reference of the LDO stable. It charges up the capacitor and that is tied to the bandgap as the reference voltage. So voltage should be developed and roughly 1.5uA max should be expected from this pin.

    Regards,

    John

  • 0 in reply to John Schneider
    Expert 1210 points

    But now that we test it out, we find that there is a voltage of 1.2V in this position. What is the situation here

  • 0 in reply to user6350528
    TI__Genius 12511 points

    Hi,

    There should be a voltage of 1.23V developed at this pin for all devices. All future devices should perform in this way with that voltage at the bypass pin on the device. The older devices should have this as well as that is the proper operation of the LDO.

    Regards,

    John