TPS65131: Pos and Neg voltage issues

Denny Varghese

Prodigy 160 points

Part Number: TPS65131

Hi Team, We have designed the dual power supply using the IC TPS65131 to get +12V and -12V with 5v as input.

For this we have Chosen the below resistor values:

R1=976K ohm, R2=110K ohm as per the relation R1=R2*((V_pos/V_ref)-1)

R4=133K ohm, R3=1.3M ohm as per the relation R3=-R4*(V_neg/V_ref)

In our schematics (attached), R1=R34, R2=R36, R4=R35, R3=R38

WEBENCH TOOL shows the same resistor values as per the above calculations for +/-12V.

But we obtained the following values when a 5V input is supplied without any load.
Positive voltage = +16.5 V
Negative Voltage = -17.8 V

Please let me know the changes/updates required in the design, so as to get the positive voltage of +12V and the negative voltage -12V.

I really appreciate your help in this. Thank you.

over 5 years ago

0 Aaron Goodson over 5 years ago

TI__Expert 6330 points

Hi Denny,

I have notified our expert regarding this topic. Please expect a response by 10/17/18.

Thanks,
Aaron

0 Liaqat Khan over 5 years ago

TI__Mastermind 18550 points

Hi Denny,
Overall, your schematics looks good. On some board layouts, we have noticed that there is excessive noise coupling into FBN pin via the feed-forward capacitor C45. To reduce this noise coupling we recommend using a 51.1K series resistor at R39. can you add that to see if the voltage regulation gets better? The only other thing that I can think of is perhaps wrong valued components stuffed at board assembly even though the schematics shows correct components. So please do check that correct components are installed on the board.
Kind Regards,
Liaqat

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TPS65131: Pos and Neg voltage issues