PCM4222: Interference Issues in Multi-PCM4222 Applications

user5847008

Part Number: PCM4222

Tool/software:

Hi,

I have designed a functional test (FT) board using the PCM4222, with a total of 4 sites, each equipped with one PCM4222. I’ve encountered an issue where using the ADCs simultaneously causes interference between them. The main problem is the appearance of low-frequency noise, leading to ADC output not meeting expectations. When only one site is active and the others are turned off, the tests perform normally.

Could you suggest potential approaches to improve this situation? Would you recommend adding more LDOs to isolate and prevent power supply interference? The analog/digital interfaces for different sites are independent. Could this be a clock interference issue affecting the ADC and causing aliasing problems as well?

Thank you.

1 month ago

0 Daveon Douglas 1 month ago

TI__Mastermind 22500 points

Hi,

Can you please share your schematic?

0 user5847008 1 month ago in reply to Daveon Douglas

Prodigy 10 points

Hi,

Thank you for the reply.
Please refer to the schematic. S0_xxx represents those nets at site number 0, and there are a total from S0_ xxx to S3_xxx.

Thank you.

0 Daveon Douglas 1 month ago in reply to user5847008

TI__Mastermind 22500 points

Hi,

Thanks for sharing i'll review and provide any comments.

Since the issue only arises when multiple devices are enabled, do they all share the same power rail and GND? Noise could be coupling into the ADC input if there are multiple power supply sources and GND's resulting in ground loop issues.

0 user5847008 1 month ago in reply to Daveon Douglas

Prodigy 10 points

Hi,

OK! Thanks.

For the situation described above, these four sites all share the same power rail and GND in the PCB’s power/ground layer: ATX_+5V, ATX_+3.3V, and DGND.

0 Daveon Douglas 1 month ago in reply to user5847008

TI__Mastermind 22500 points

Willl update within 12 hours

0 user5847008 18 days ago in reply to Daveon Douglas

Prodigy 10 points

Hi Sir,

Are there any suggestions for improving the schematic following the review?

Thanks!

0 Jeff McPherson 17 days ago in reply to user5847008

TI__Mastermind 39865 points

Hi,

Sorry Daveon is out of office until Monday.

As Daveon was mentioning, ground loop issues commonly result in low frequency noise (especially if the noise is a multiple of 50 or 60Hz).

Isolating the power supplies and grounds sounds like the best option. It's unlikely that this is a clock problem or aliasing problem.

Best regards,
Jeff McPherson

0 user5847008 15 days ago in reply to Jeff McPherson

Prodigy 10 points

Hi,

OK, we will check the design.

Thanks!

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PCM4222: Interference Issues in Multi-PCM4222 Applications