PCM4201: Vref failure

Elliott Whyte

Part Number: PCM4201

Hi,

I have a higher than expected failure rate for the PCM4201. On 3 chips the audio performance was below the correct quality standard. It was found that the voltage across the Vref pins was wrong (e.g 4.2V), instead of the 2.5V that should be present. There are very few supporting components for this part of the chip so I am struggling with what part of our implementation could cause the issue. I have the recommended 100n cap near to the chip with a 22uF electrolytic nearby also. The next logical area of the circuit that could cause this is the Vcc input, but that looks correct and is fed from its own dedicated regulator nearby to the chip. I cannot see any power supply sequencing requirements mentioned in the datasheet either. Is this a known fault or do you have a suggestion of what could cause this?

Thanks

over 3 years ago

0 Sanjay Dixit over 3 years ago

TI__Mastermind 23030 points

Please check DC Resistance to GND of Vin+,Vin -,Vref and Vcc pins and compare with a good device.

There is a chance that a transient on Vin+ or Vin- lines has resulted in the fault. Are the any current limiting resistors in series with analog inputs Vin+ and Vin- ?

The VREF - must be tied to analog ground. Also check if any switching trace is running close to the Vref Line. It may be coupling something into the vref.

0 Elliott Whyte over 3 years ago

Prodigy 90 points

Hi Sanjay,

OK, thanks for the suggestions. I will test those and let you know the result.

Thanks

0 Sanjay Dixit over 3 years ago in reply to Elliott Whyte

TI__Mastermind 23030 points

SURE.

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PCM4201: Vref failure