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LP5907-Q1: Vout abnormal

Darren Yang
Expert 2000 points
Part Number: LP5907-Q1
Other Parts Discussed in Thread: LP5907

we use LP5907 to design for Vin：4.5V  vout：3.3V/100mA,however，now we meet question is same problem board is Vout  only 1.45V when the Vin is 4.5V,the Schematic diagram as below，could help give some suggest to solve it，besides，maybe the L10 can impact it when the input Power off instantly？

  • 0
    TI__Guru 55940 points
    Hi Darren,

    LP5907 requires at least a 1uF capacitor local to the LDO output. In your schematic this would be between Vout and FB331. This local capacitor is required for a stable output.

    Very Respectfully,
    Ryan
  • 0 in reply to Ryan Eslinger
    Expert 2000 points
    Hi Ryan，in my Schematic I place 22uf capacitor behind the FB331，is necessary place t least a 1uF between Vout and FB331？now we have found 4pcs is failure, is it possible LP5907 is dad，What steps should I do to authenticate? Could you give some suggestion，tks！
  • 0 in reply to Darren Yang
    TI__Guru 55940 points

    Hi Darren,

    Yes the output capacitor needs to be local to the LDO (before any other external components).  This is true of most linear regulators.  While LP5907 does allow for remote capacitors, this is a reflection of distance rather than allowing for external components to be between the LDO and the output capacitor.  Please note that when remote sensing the inductance between the capacitor and OUT pin should be less than 35nH.

    Very Respectfully,

    Ryan