What voltage range can be measured with the ADC?

[Guest]

What voltage range can be measured with the ADC on the nRF51 series?

[Stefan Birnir Sverrisson]

There are basically two rules to follow when deciding max voltage on AIN pins:

1. The ADC should not be exposed to higher voltage than 2.4V on an input pin AIN after prescaling
2. GPIO pin should not be exposed to higher voltage than VDD+0.3V, see Aboslute maximum ratings in the nRF51822 PS

For example, when having 2/3 prescaling you can expose 2.4V/(2/3)=3.6V to an AIN pin. For not to violate rule 2, VDD should be 3.3V or higher in this case.

These are the maximum voltages that can be exposed to an ADC AIN pins, depending on supply voltage and your prescale settings: VDD 3.6, prescaling 1/1: AIN max 2.4V (rule 1 limitation) VDD 3.6, prescaling 2/3: AIN max 3.6V (rule 1 limitation) VDD 3.6, prescaling 1/3: AIN max 3.9V (rule 2 limitation) VDD 3.3, prescaling 1/1: AIN max 2.4V (rule 1 limitation) VDD 3.3, prescaling 2/3: AIN max 3.6V (rule 1 and rule 2 limitation) VDD 3.3, prescaling 1/3: AIN max 3.6V (rule 2 limitation) VDD 1.8, prescaling 1/1: AIN max 2.1V (rule 2 limitation) VDD 1.8, prescaling 2/3: AIN max 2.1V (rule 2 limitation) VDD 1.8, prescaling 1/3: AIN max 2.1V (rule 2 limitation)