tps62732 wrong output voltage

lakshmikanth satyavolu

Other Parts Discussed in Thread: TPS62732

Hello,

I am using TPS62732 in my design to power up SPI flash memory (Cypress's S25FS256SAGNFI001). I have attached the schematic for reference.

There is a problem in voltage output from TPS62732 when Flash chip mounted. My Observations are below.

Please let me know if anything wrong with the circuit or any suggestions would be highly appreciated.

Observations:

BEFORE FLASH MEMORY IS SOLDERED.

Output of U6 regulator (TPS62732) is 1.9V

AFTER THE FLASH MEMORY IS SOLDERED

Output of U6 regulator (TPS62732) is fixed anywhere between 2.2V and 3V .

Any suggestions on what could be going wrong?

DI_5/ON-BYP-TPS62732 = HIGH = 2.8V
DI_4/ON-TPS22860 = HIGH = 2.8V

Regards

Lakshmikanth.

over 7 years ago

0 Chris Glaser over 7 years ago

TI__Guru*** 143680 points

I edited the title of your post to state what the issue actually is.

Can you post a waveform of Vin, Vout, SW, and ON/BYP when the voltage is not correct?

Can you show the connections to the ON/BYP pin?

0 lakshmikanth satyavolu over 7 years ago in reply to Chris Glaser

Expert 1620 points

Hi Chris Glaser,

Thanks for response.

I have attached scope waveforms on the Vin,Vout,SW and ON/BYP pins. I also attached ON/BYP pin driving schematic from processor. Please review.

Regards

Lakshmikanth.

0 Chris Glaser over 7 years ago in reply to lakshmikanth satyavolu

TI__Guru*** 143680 points

Thanks for sending. Since there is no activity on SW, the high output voltage is coming from somewhere else in the system. It is likely being backfed through the flash. You can check what other voltages are present on the flash and where there could be leakage paths (through its ESD circuits or pull-up resistors) back to this 1.9Vout.

0 lakshmikanth satyavolu over 7 years ago in reply to Chris Glaser

Expert 1620 points

Hi Fredrik,

You are right. Other IO pins of the flash chip which are driven by processor are causing the high voltage. When I disable the IOs voltage from processor, I dont see high voltage.

Is there any work around to prevent the voltage fed back by processor IOs connected to flash chip?? Please suggest.

Regards

Lakshmikanth

0 lakshmikanth satyavolu over 7 years ago in reply to lakshmikanth satyavolu

Expert 1620 points

Hi Chris Glaser,

You are right. Other IO pins of the flash chip which are driven by processor are causing the high voltage. When I disable the IOs voltage from processor, I dont see high voltage.

Is there any work around to prevent the voltage fed back by processor IOs connected to flash chip?? Please suggest.

Regards

Lakshmikanth

0 Chris Glaser over 7 years ago in reply to lakshmikanth satyavolu

TI__Guru*** 143680 points

You should be able to check with the flash provider if this is an errata of theirs and/or if they have a workaround.

You can usually overcome this issue by adding a diode in your circuit to keep the higher voltage out of where it shouldn't be.

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tps62732 wrong output voltage