the snubber circuit on the internal DC/DC regulator

[Kiyoshi Iwai]

Hello,

To improve the performance of SAADC, I would like to isolate the SAADC from the bad effect of DC/DC and RF.

I assume that SAADC has some noise because of DC/DC operation.

Could I add the snubber circuits between the terminal "DCC" and GND?

Any problem?

If you have other effective solutions, let me know them, please.

Best regards,

Kiyoshi Iwai

[ketiljo]

Dear Mr. Iwai

I have asked the designer about this and this is the answer I got from him: 

"A snubber to DCC pin is traditional method to attenuate HF noise. It could work for noise on 8MHz harmonics, but I doubt SAADC can be disturbed at that frequency range, but contamination comes from fundamental 8Mhz conducted via supply.

 The snubber will take dynamic power lowering DCDC efficiency. Also the effectiveness in hard to predict as it depends on PCB placement and routing.

 Can’t they circumvent by ADC config, use more averaging, do it differential or other ?"

Best regards,

Ketil Aas-Johansen

[Kiyoshi Iwai]

Hello Ketil,

Thank you for reply.

I have already used averaging and differential mode.

Anything else?

best regards,

Kiyoshi Iwai

[ketiljo]

Hello Kiyoshi 

I don't have any other suggestions, sorry. Sounds like you have reached the point where you can't get better performance of the ADC. Do you see a difference in noise when the ADC is on or off?

best regards,

Ketil