TPS51200: No REFOUT, no VO

Vadim Lazarev2

Part Number: TPS51200

Good day!

I'm using TPS51200DRC for generating Vtt for DDR4 memory (use no REFOUT) and have no output signals, except PGOOD. Here is my schematic:

+3V3 turns on first (and enables IC) then +1V2. Though there is +3V3 and +1V2 I have 0 on REFOUT and 60mV on VO and pulled-up (externally) PGOOD. Tried to change REFOUT capacitor with no result. Checked all inputs and they are OK.

Can you help to solve this problem?

Best regards, Vadim.

over 5 years ago

0 Qian Chen over 5 years ago

TI__Mastermind 24075 points

HI Vadim,

Your schematic does not show up. Can you provide it again?

Also, can you check REFIN voltage?

Thanks

Qian

0 Vadim Lazarev2 over 5 years ago in reply to Qian Chen

Prodigy 90 points

REFIN is 0.6V.

Best regards, Vadim.

0 Qian Chen over 5 years ago in reply to Vadim Lazarev2

TI__Mastermind 24075 points

Hi Vadim,

Refout follows Refin, and Vout follows Refout. I suspect something happens on Refout pin.

Can you check C535 to a small value such as 0.1uF?

Is Refout connected to external circuit except the bypass cap? Can you check the impedance between Refout and ground to see if it is pulled low externally?

Thanks

Qian

0 Vadim Lazarev2 over 5 years ago in reply to Qian Chen

Prodigy 90 points

Tried 0.1uF. Refout is connected to bypass cap only and impedance to gnd is about 100KOhm.

It appears that I could measure Vtt with DRAM module onboard only. When I created this topic I tried without DRAM modules expecting to check Vtt or Vref without damaging module in case of something. Is there reference on it in datasheet? If Refout follows Refin, still why I dont see Refout without DRAM onboard?

During testing I noticed that PGOOD operates independent to EN pin. Why could this happen?

Best regards, Vadim.

0 Qian Chen over 5 years ago in reply to Vadim Lazarev2

TI__Mastermind 24075 points

Hi Vadim,

I don't know what happens on your board, but TPS51200 should work without DRAM module.

For the PGOOD, is there a external pull-up resistor?

Thanks

Qian

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TPS51200: No REFOUT, no VO