VDDH measurement with the ADC (nrf52840 QIAAC0)

RE: VDDH measurement with the ADC (nrf52840 QIAAC0)

haakonsh — Tue, 03 Sep 2019 08:33:07 GMT

I understand the confusion, my best guess is that the analog reference of VDDH/5 is sampled somewhere in the regulator's internal circuit who's not in its operational state, as opposed to the VDDH input pin.

RE: VDDH measurement with the ADC (nrf52840 QIAAC0)

Abderrezak Mekkaoui — Mon, 02 Sep 2019 14:34:29 GMT

Thank you. The documentation states that the input to the ADC could be VDD, VDDH/5,AIN0.....Somewhat misleading. Just wanted to make sure the beahavior is expected because in the case VDD=VDDH, measuring VDD is enough.

RE: VDDH measurement with the ADC (nrf52840 QIAAC0)

haakonsh — Mon, 02 Sep 2019 13:36:29 GMT

Aah, now I understand.

Well, that is undefined behavior, as the REG0 is not in use measuring the voltage of its output makes little sense.

Hope that clarifies it a bit.

RE: VDDH measurement with the ADC (nrf52840 QIAAC0)

Abderrezak Mekkaoui — Mon, 02 Sep 2019 13:09:20 GMT

Hi Haakonsh

VDDH not connected to VDD => VDDH is supplied externally. VDD is provided by the nRF chip. Figure 209: Circuit configuration no. 2 schematic

VDDH connected to VDD => VDDH is shorted to VDD and supplied externally. Figure 210: Circuit configuration no. 3 schematic.

In both cases NO DCDC is used. (Both DCDC regulators are disabled: DCDCEN0=0; DCDCEN1=0).

Ref. nRF52840 Product Specification v1.0

Thanks

RE: VDDH measurement with the ADC (nrf52840 QIAAC0)

haakonsh — Mon, 02 Sep 2019 08:43:11 GMT

[quote user=""] In normal mode (VDDH not connected to VDD) the reported results are good (3.0V and 1.8V for example).[/quote]

What do you mean by "VDDH not connected to VDD", that REG0 is not used?

[quote user=""]But in high voltage mode (VDDH connected to VDD), the VDD measurement is correct but not that of VDDH (1.9V and 3V) instead of (3V and 3V).[/quote]

Can you show us a schematic of the two modes you are referring to, and tell us when you are using REG0?