nRF54L15 ADC documentation, confusing statement about voltage range in single-ended mode

[cyber_v1]

In the documentation, it is stated:

The SAADC is preceded by a gain stage which has a programmable gain. The voltage range seen at the input of the gain stage is:

...

​​VRangeSingleEnded = ± 0.5*VREF/GAIN

This is quite confusing; why is the low end of the range negative and not zero, if in single-ended mode, the negative input is shorted to ground internally? Why is the high end of the range only half of the VREF?

[Einar Thorsrud]

Hi,

This is a typo in the datasheet. The "±" should not be part of the formula. In single ended mode, the SAADC works just like differential mode, only that the negative input is shorted to ground. Therefore, it is correct that the range for single ended if half the range for differential (as you only use the positive half of the full range).

[cyber_v1]

Hi! Thank you for the confirmation!

Is the 0.5 also the mistake then?

If the full differential range is VRangeDifferential = ± VREF/GAIN, then the half of it is just 0 to VREF/GAIN, not 0 to 0.5*VREF/GAIN.

[Einar Thorsrud]

Hi,

You are right. The correct formula for single ended should be VRangeSingleEnded = VREF/GAIN. This has been reported and should be fixed in a future data sheet revision.

[cyber_v1]

Amazing! Thank you!