TPS23757EVM: Vref is not 1.25V or Output voltage is not 5V

Zhou Xiang

Part Number: TPS23757EVM
Other Parts Discussed in Thread: TPS23757, TL431

Hi Bro,

Recently we designed in TPS23757 into our application. But now the IC TPS23757 creats much heat and output voltage is 5.6V. Even we adjust resistor R32 and R34 value, output voltage doesn't change.

We also tested U3, its vref=1.87V. Seems wrong which is not 1.25V.

Could you give us a direction how to check and solve this problem?

BDs,

Xiang

over 2 years ago

0 Zhou Xiang over 2 years ago

Prodigy 10 points

0 Diang Xing over 2 years ago in reply to Zhou Xiang

TI__Mastermind 35471 points

Hi Xiang,

Thanks for reaching out!

Because of the Fourth of July holiday, TI E2E design support forum responses may be delayed from July 3 through July 4. Thank you for your patience.

I will be back in July 5th.

Best regards,

Diang

0 Diang Xing over 2 years ago in reply to Diang Xing

TI__Mastermind 35471 points

Hi Xiang,

TL431 has 2.5-V Vref. With your R131 and R129 values, you are supposed to have ~12.5-V Vout.

Your transformer is for 5-Vout design. The transformer's turns ratio may cause the TPS23757 reach its max duty cycle (76%), which will make your Vout be clamped.

Best regards,

Diang

0 Diang Xing over 1 year ago in reply to Diang Xing

TI__Mastermind 35471 points

Hi Xiang,

Since we have not got your response for a relative long time, I will close this thread for now. Please rely or open a new thread if you have any further questiosn.

Best regards,

Diang

Power management

Power management forum

TPS23757EVM: Vref is not 1.25V or Output voltage is not 5V