• State Resolved
  • Locked Locked
  • Replies 3 replies
  • Answers 1 answer
  • Subscribers 64 subscribers
  • Views 231 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

Original question:

LM27762: OUT- could not startup when it is pre-charged to positive?

LM27762: About leak current path

teritama
Expert 1790 points
Part Number: LM27762

Hi team,

In the case that positive and negative output voltage supply at same time, the leak current between OUT+ to OUT- may affect for OUT- output.

I think this leak current path which can through biggest leak current is FB resister line. Is this correct?

If there is some leak current path included in this device, let me tell.

Best regards,

teritama

  • 0
    TI__Genius 17350 points

    Hi Teritama,

    There should be no leakage between both the OUT+ and OUT- rails. For example if you consider the OUT+ rail, the GND is shorted to the CIN and COUT caps and the return currents will flow to these caps instead of passing through the OUT- rail.

    The only leakage will be through the FB resistors of each rail to GND.

    Best regards,

    Varun

  • 0 in reply to Varun John
    Expert 1790 points

    Hi Varun,

    Thank you for reply.

    I understood that there is no leak current between OUT+ and OUT- in LM27762.

    Does this mean that we should pay attention positive pre-bias on negative voltage rail when using single output charge pomp device (ex.LM2667) only and the positive pre-bias occurring on OUT- rail is unlikely  when using LM27762?

    Best regards,

    teritama

  • +1 in reply to teritama
    TI__Genius 17350 points

    Hi Teritama,

    There can be certain application scenarios where the negative rail can get pulled positive by the load before the charge pump is turned on. This is because of the load connected to the negative rail. Section 8.4.1 of the datasheet of TPS60400 explains this.

    The positive rail of LM27762 shouldn't cause any positive pre bias on the negative rail.

    Best regards,

    Varun