ADS1251: Sigma-Delta switching frequency synchronization

Hi Daniel,

The best choice would be to use an LDO on the output of the transformer to clean up the signal and reject some of the higher frequency content.

Here is some other content to pass along to the customer to help with this issue:

• https://www.allaboutcircuits.com/industry-articles/resolving-the-signal-part-11-how-power-supply-noise-affects-delta-sigma-ADC/
• https://www.allaboutcircuits.com/industry-articles/resolving-the-signal-part-12-reducing-the-effects-of-power-supply-noise-usi/

Let me know if they have any additional questions

-Bryan

Hi Daniel,

If this is a noise critical application, an LDO should be a no-brainer.

Otherwise, they can try to follow some of the suggestions in the content I linked to in my last post. Specifically they want to make sure to that the switching frequency is far away from modulator frequency (fMOD) such that the digital filter removes some of the noise power introduced by the DC/DC.

I am not sure what he means about synchronization. The delta-sigma ADC continuously converts during the conversion period, so unless they plan on using a much higher-speed ADC to try to finish conversions within the DC/DC switching frequency period, I don't really know what they are after (though this would increase the noise).

Again, they really should just use an LDO.

-Bryan