nRF51822, what is the input current/impedance

RE: nRF51822, what is the input current/impedance

thorXI — Thu, 10 Mar 2016 03:41:04 GMT

The impedances given above for the ADC pins are not consistent with the white paper available elsewhere on Nordic Dev Zone: http://tinyurl.com/hzeayvz --- Which of the two sources has the correct answer?

RE: nRF51822, what is the input current/impedance

Ronnie Bajwa — Fri, 22 Aug 2014 00:56:25 GMT

Hi, can you comment on the expected variation for the 1/3 prescaling case. Would it be within 10% of 550 kohm?

RE: nRF51822, what is the input current/impedance

Petter Myhre — Thu, 05 Dec 2013 10:03:59 GMT

The leakage current of the GPIOs should be in the order of a few nA.

I don't have any more information, but I can try to aquire some, if you could be a bit more specific on what you need.

RE: nRF51822, what is the input current/impedance

Russ Mirov — Thu, 05 Dec 2013 07:38:45 GMT

Hi Petter. For my application I do need more information I'm afraid. "close to infinity" is difficult to design with. Is the input leakage current for a GPIO configured as a digital input (and with no pullups/pulldowns enabled) xx uA, nA, fA ? Often it can depend on DC bias as well as temperature. Is any of that information available ?

Thanks.

RE: nRF51822, what is the input current/impedance

Petter Myhre — Wed, 02 Oct 2013 09:15:39 GMT

The input impedance for a digital input pin is close to infinity when it's configured as an input, and to zero when it's configured as an output.

The analog input pins belong to the ADC, and the prescaler setting will affect their input impedance.

EDIT 2016.03.29: New values can be found in the nRF51 Reference Manual V3.0, Chapter 31.1.3:

Prescaling 1/1: Mean impedance 129.7 kΩ Standard deviation 2.74 kΩ
Prescaling 2/3: Mean impedance 194.6 kΩ Standard deviation 4.1 kΩ
Prescaling 1/3: Mean impedance 389.2 kΩ Standard deviation 8.2 kΩ

The inputs also have some capacitance, 3-4pf.