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.

LM2776: Output voltage not good

Part Number: LM2776

Hello team,

Could you please help me to address issue on the output voltage?

The issue is exactly same as one discussed on E2E thread here. But unfortunately this was solved offline.

I'm trying to output -5V from 5V input but my LM2776 outputs +0.7V.

Please find schematic from internal link here.

Best regards,

Itoh

  • Hi Itoh-san,

    The schematic diagram looks fine. To understand the issue better, can you provide the following items:

    1. PCB layout

    2. Vin, Vout, Iout waveforms

    3. Waveform across C1+ and C1-

    Best regards,

    Excel

  • Hi Excel-san,

    Please find the layout from the internal link here.

     As I don't have the board in my lab, let me explain about the waveform.

    Vout is almost constant +0.7V. C+1 is not switching. It keeps constant approx. +5V.

    Does it make sense?

    Regards,

    Itoh 

  • Hi Itoh-san,

    Is the layout you shared the top or bottom view? Because if it is the bottom view, then the pin orientation is incorrect and it will not provide the correct output voltage.

    To better understand the issue, please capture the waveforms with the following conditions:

    1. Vin, Vout, C1+ with respect to GND pin

    Best regards,

    Excel