LM2776 - Output not correct : -1.2V output not -5V (charge pump invertor )

PARMANAND JOSHI

Other Parts Discussed in Thread: LM2776

I am having an issue with a prototype design with the LM2776. I have followed the suggested layout and component suggestions, but when I look at the output without a load, the output is -1.2V and not -5V (VIN is 5V) .

Any help or suggestions would be greatly appreciated.

Schematic:

over 8 years ago

0 Juha Karttunen over 8 years ago

TI__Intellectual 1120 points

Hi PARMANAND JOSHI ,

Datasheet instructs placing input,output and flying capacitor on same layer as LM2776 and keeping connections as short and wide as possible. Looking at your PCB layout, it seems that there is no short connection from C41- to ground pin or from C42- to ground pin.

See similar discussion thread: e2e.ti.com/.../471527

Regards,
Juha

Power management

Power management forum

LM2776 - Output not correct : -1.2V output not -5V (charge pump invertor )