TPS23757: Bring-up and troubleshooting guide

Michael Gilge

Part Number: TPS23757

Hello, I have duplicated the design of the TPS23757EVM but it is not working. For space reasons I used a different gate drive transformer TDK/EPCOS B82804A0354A110 and the Wurth Elektronik 749 119 350 transformer. My board is making audible noises and the synchronous rectifier MOSFET Q1 is overheating. Is there a procedure or best practice for troubleshooting?

over 5 years ago

0 Darwin Fernandez over 5 years ago

TI__Mastermind 40885 points

Hi Michael,

I have not used the TDK part in the past. This could be a shoot through issue. You should look at the waveform of the VDS of both the primary and synch FET to see if they is a long time they are both ON at the same time. In which case you may need to increase R14 to slow down the synch FET.

Regards,

Darwin

0 Michael Gilge over 5 years ago in reply to Darwin Fernandez

Expert 1720 points

Hi Darwin,

thanks for your input. Here are some remarks:

1. Do you have a sample VDS waveform for the primary and secondary MOSFETs? I cannot record both waveforms at the same time, because the ground is different.

2. R14 is currently zero ohms. What value should I try?

3. The TDK transformer has less inductances: 350 uH vs. 1200 uH of the PA0184.

4. The DT resistor of the EVM is only 10k, the data sheet calls for 50k.

Best regards,

Michael

0 Michael Gilge over 5 years ago in reply to Darwin Fernandez

Expert 1720 points

Hi Darwin,

I have increased the RDT from 10kohms (EVM) to 50kohms (datasheet). The converter only starts, when I touch primary and secondary side with my fingers. I guess it needs some capacitive loading? Otherwise it continues trying to start. Once it has started it runs fine. Any suggestions?

Michael

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TPS23757: Bring-up and troubleshooting guide