TPS51200: Why TPS51200 VTT output dropped ?

Hi Dave,

Can you check if VREFIN voltage or REFOUT voltage drops?
Also, can you provide the VTT waveform?
It will be good if you can provide the schematic, so we can review the schematic.

Thanks
Qian

Dear Qian,

The VREFIN voltage or REFOUT didn't drop, they are constant as +1.5V and +0.75V.

The VTT maintains at +0.032V or +1.2V after it drifted from +0.75V.

Please check the attached TPS51200 configuartion in my desing.

In my design, SODIMM is utilized.

Please let me know any answers.

Many thanks.

David

Dear Qian,

The schematics for TPS51200 and SODIMM interface are attached in below.

David

HI David,

The schematic looks fine.

• Can you probe REFIN, REFOUT, VTT voltage at the same times and provide the waveform?
• One possibilty is VTT instant current triggers OC. Can you keep FPGA off and apply electronics load and check if VTT is out of regulation. Increase current from 0A to 3A gradually.
• Check if 3.3Vin is stable during FPGA programming.

Thanks

Qian

Dear Qian,

I will follow your suggestions and provide any results to you.

Currently, the weird this is after we progrem FPGA the VTT boosted upto +1.2V instead of dropping.

Please let me know if the VTT boosting is resulted from IC latchup, because of FPGA code probelm.

Many thanks.

David.

Dear Qian,

We finally found out the problem.

We forgot setting the Enable pin of TPS51200 to "High".

Currently, The VTT of SODIMM is under normal condition with loaded memroy code.

Many thnaks for your helps and Best Regards.

David.

Thanks for the update.