nRF5340 ADC reference and gain questions

RE: nRF5340 ADC reference and gain questions

ovrebekk — Fri, 10 Jun 2022 07:02:11 GMT

Hi Doug

Good to hear that you got what you need. I will close the case then 🙂

Best regards
Torbjørn

RE: nRF5340 ADC reference and gain questions

dyoung.mpd — Wed, 08 Jun 2022 15:25:23 GMT

Hi Torbjorn,

Thank you for your response. I read it quickly when you had first posted it but at that time I had been pulled into other projects and did not have time to fully digest your response. I was able to review it today and I see that you have given me the information I needed to answer my questions.

Thank you for your support and you can consider the question to be resolved if you haven't already done so.

Sincerely,

Doug Young

RE: nRF5340 ADC reference and gain questions

ovrebekk — Tue, 16 Nov 2021 10:37:50 GMT

Hi Doug

I am very sorry for the slow response. You will find a response to your questions below:

[quote user=""]In the nRF5340 product specification version 1.2, I see an internal bandgap reference error range of -1.8/+0.5%.

Is this the same internal reference used by the ADC?

[/quote]

No, the referred reference is used for the COMP peripheral, not the ADC.

[quote user=""]Is this the reference error over the recommended operating temperature range of the nRF5340?[/quote]

Reference error is accounted in Gain error parameters in the product specification (SAADC Electrical specification chapter), and the gain error temperature coefficient is given by the C_EG parameter.

[quote user=""]I see in older RF development zone cases, such as case ID: 268846, that the room temperature reference error is +-0.2%. Is this error still applicable to the nRF5340[/quote]

Yes, the case you refer to is for the nRF5340.

[quote user=""]How stable is the reference error over time?[/quote]

If the temperature and voltage is stable the reference should have negligible variation.

[quote user=""]The nRF5340 product specification also lists gain errors from -3% to +3% (+4% for G=0.5, G=1)

Is this the gain error over the recommended operating temperature range of the nRF5340?

[/quote]

No. As stated in the footnote in the product specification, temperature is not included. You have a dedicated parameter for the gain error temperature coefficient.

[quote user=""]How stable is the gain error over time?[/quote]

Gain error is stable as long as voltage and temperature stay unchanged.

[quote user=""]Are gain values < 1 realized by tap points on the resistor ladder?[/quote]

[quote user=""]If we use a gain value < 1, is there an additional series source resistance that we have to account for when calculating minimum ADC acquisition time?[/quote]

No. Section 7.29.9 in the product specification applies independently of gain setting.

Best regards
Torbjørn

RE: nRF5340 ADC reference and gain questions

dyoung.mpd — Mon, 15 Nov 2021 19:05:50 GMT

Hi Torbjorn,

Do you have any updates or a schedule from the team as to when this will be addressed?

Sincerely,

Doug Young

RE: nRF5340 ADC reference and gain questions

ovrebekk — Fri, 29 Oct 2021 10:37:23 GMT

Hi Doug

I haven't gotten a response yet unfortunately. I have asked the team if they can provide a schedule for when this work can be done.

Best regards
Torbjørn

RE: nRF5340 ADC reference and gain questions

dyoung.mpd — Thu, 28 Oct 2021 14:49:06 GMT

Hi Torbjorn,

Have you received a response from the hardware team?

Sincerely,

Doug Young

RE: nRF5340 ADC reference and gain questions

ovrebekk — Thu, 21 Oct 2021 11:18:29 GMT

I have forwarded your questions to the hardware team, and I will let you know when I hear back from them.

Best regards
Torbjørn