ADC internal ref accuracy compared to VDD/4 as ref

RE: ADC internal ref accuracy compared to VDD/4 as ref

Karl Ylvisaker — Tue, 18 Jan 2022 12:01:35 GMT

[quote user="MrQuincle"]Resolved.[/quote]

Great, I am happy to hear that, Anne!

[quote user="MrQuincle"]If we have further questions we will use DMs given the confidential nature of the topic matter.[/quote]

Yes, or alternatively you could raise it as a private ticket - this would be preferable to Direct Messages.

Best regards,
Karl

RE: ADC internal ref accuracy compared to VDD/4 as ref

Anne van Rossum — Tue, 18 Jan 2022 11:48:40 GMT

Resolved. If we have further questions we will use DMs given the confidential nature of the topic matter.

RE: ADC internal ref accuracy compared to VDD/4 as ref

Karl Ylvisaker — Tue, 18 Jan 2022 10:32:30 GMT

Great!
I have informed the RSM that you will be in contact about this matter soon.

Best regards,
Karl

RE: ADC internal ref accuracy compared to VDD/4 as ref

Anne van Rossum — Tue, 18 Jan 2022 10:10:18 GMT

I'll organize it.

RE: ADC internal ref accuracy compared to VDD/4 as ref

Karl Ylvisaker — Fri, 14 Jan 2022 18:23:45 GMT

Hello Bart,

We have some additional information about the SAADC that is only available under NDA.
You may reach out to your Regional Sales Manager (RSM) to arrange the signing of the NDA so that we may provide you with this extra information. If you do not know who your RSM is please send me a direct message with your location, so that I may provide you with their contact information.

Best regards,
Karl

RE: ADC internal ref accuracy compared to VDD/4 as ref

bart — Fri, 14 Jan 2022 13:13:28 GMT

Yes, that makes sense. However, suppose the signal is unrelated to VDD, but we have a perfect VDD of 3.3V, then what kind of gain error would I get? Basically I'm trying to find out what the error of the internal ref is, separately from the gain error.

RE: ADC internal ref accuracy compared to VDD/4 as ref

hmolesworth — Thu, 13 Jan 2022 15:54:01 GMT

Depends more on whether the signal is ratiometric or not. If the signal is unrelated to VDD, for example an external device like a tiny photocell which generates a voltage completely independent of nRF52 VDD then the internal reference will always be better. However if the signal voltage is related to VDD such that it rises and falls as VDD rises and falls (say a potentiometer or load cell which uses VDD as the voltage source) then VDD/4 will be more stable as the reference VDD/4 tracks the excitation voltage.