Reference Accuracy

[slight]

I cannot find a specification for the SAADC converter's reference accuracy. The product specification indicates it is 0.6V, but beyond that I cannot find anything. Looking for absolute accuracy at room temp, over operating temperature range and any drift specification available.

Also, is there any guidance for GPIO voltage and input voltage range for best ADC accuracy? Ie., is it better to have a 3.3V VGPIO and ADC input range up to 3.3V, or a 1.8V VGPIO with ADC input range of 1.8V (assuming external circuitry can bring the input signal to the desired range.) Or, does it matter (ie., could have VGPIO=3.5V with ADC input range of 2.5V and use the internal reference.)

Any general guidance on attaining best ADC accuracy? Ie., better to use internal reference or external reference feeding GPIO (or one of the inputs assuming input signal is single ended.)

[roryelila]

Using an external reference voltage source can improve the reference accuracy of the ADC. External reference voltage sources are often more stable and accurate than internal reference voltage sources. However, they can be more expensive and require additional circuitry. 

slope

[Unknown]

As per my read of the datasheet, the main choices for reference are VDD_GPIO or the inner reference. Given the condition for the result code incorporates this reference, it seems important to give an outside reference to VDD_GPIO for best exactness. It will be necessary to apply the external reference to VDD_GPIO as well, as I need to know how much current VDD_GPIO will draw, since applying an external reference to one of the input pins as you suggest will affect the output code. delta executor