LM27762: the output of -2.5v is only about -1.6v, and powergood is always high

user5707026

Part Number: LM27762

Dears

The input voltage is 3.9;
When there is no load, the output of -2.5v is only about -1.6v, and powergood is always high.
When this phenomenon occurs, the voltage of FB-PIN is -0.8V, and FB- is -1.22V in the specification when it is normal.
How can there be ±2.5V output;
Below is the circuit schematic

over 5 years ago

0 Febin over 5 years ago

TI__Mastermind 25430 points

Hi,

I reviewed the schematic and everything looks fine.

I would like to suggest a few things:

1. Please ensure that you have a stable input supply.

2. Could you please change the IC or swap with an EVM. May be it is already damaged.

3. How many boards have this issue?

4. Is it possible to share all the measurements plots for Vin, Vout+/-, Ccp, Cfly, Iout+/- and the layout?

Regards,

Febin

0 Febin over 5 years ago in reply to Febin

TI__Mastermind 25430 points

Hi,

I have not heard back from you. Do you have some updates to share?

Regards,

Febin

0 user5707026 over 5 years ago in reply to Febin

Genius 3145 points

Dear Febin

Thanks for your advice.

I am still debugging, I am summing up and analyzing the phenomenon and possible problems. I will reply to you if I have a conclusion.

Thanks

Elsa Duan

0 Febin over 5 years ago in reply to user5707026

TI__Mastermind 25430 points

Hi Elsa,

Thanks for the update. Please contact us when you have some results.

Regards,

Febin

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LM27762: the output of -2.5v is only about -1.6v, and powergood is always high