SAADC external reference on nRF54L15

RE: SAADC external reference on nRF54L15

Hung Bui — Wed, 07 Jan 2026 14:53:52 GMT

Hi Fernado,

If you don't configure the EXTREF as the external reference input, I don't see a problem connecting 3.3 V to the pin.

I will report this internally to improve the documentation.

RE: SAADC external reference on nRF54L15

Fernando Fontes — Wed, 07 Jan 2026 14:17:00 GMT

Ok,.. that's a shame.. I have a pressure sensor connected and I was trying to improve the accuracy by using an external 3v3 reference to increase the scale.

The note on the datasheet should be perhaps more direct and saying that is not possible at all. I thought it was possible but it would lead to leakage and therefore waste more energy.

Ok, but nevertheless having 3v3 on EXTREF will not cause any warm on the nrf54l15 itself right? Because, it can also work as a normal gpio which should allow to go up to VDD right? Because I've a production batch already with this 3v3 on that pin.

Best regards,

Fernando Fontes

RE: SAADC external reference on nRF54L15

Hung Bui — Wed, 07 Jan 2026 14:04:54 GMT

Hi Fernando,

You can't connect 3.3V to EXTREF
It only allowed to use internal reference or external reference at (around) 0.9V.
(unlike the nRF52 that can use VDD as reference)

For doing ADC with higher than than 0.9V you will have to use GAIN or external voltage divider on the input.

RE: SAADC external reference on nRF54L15

Fernando Fontes — Wed, 07 Jan 2026 12:55:28 GMT

Ok, so if I have 3.3V connected to the EXTREF what should I do to be able to use it as the ADC reference?

Best regards,

Fernando Fontes

RE: SAADC external reference on nRF54L15

Hung Bui — Wed, 07 Jan 2026 12:49:38 GMT

Hi Metyis,

My understanding is that external reference voltage should be close to internal reference voltage = 0.9V (between 0.855V and 0.945V), not 3.3V nor 1.2V.

The reference to PADC_EXT_REF_1V2 I believe a mistake in the documentation. It's the pin on nRF54H not on nRF54L. On nRF54L external reference given at EXTREF pin.

NRF_SAADC_REFERENCE_EXTERNAL is simply a boolean bit to assign to REFSEL register to choose between internal and external reference.