Extra 5uA current draw

RE: Extra 5uA current draw

davidz — Fri, 14 May 2021 17:05:13 GMT

Thanks Marte. We have found out the reason after lots of debugging. The extra 5uA is actually from the SAADC. Somehow nrf52840DK does not show the correct current draw when measured at VDD. When we measure at the custom board with a battery, then it shows the correct current draw.

If we uninit the SAADC, then the current draw is down to 5.1uA in our custom board. This current draw matches the online profiler number very well.

RE: Extra 5uA current draw

Marte Myrvold — Fri, 14 May 2021 14:42:37 GMT

Hi,

Some of our experts are out of office until Tuesday because of public holidays in Norway. We will come back to you next week.

Best regards,

Marte

RE: Extra 5uA current draw

davidz — Wed, 12 May 2021 20:00:13 GMT

Here is some additional information: The measurement is from VDDH, not VDD on our custom board. If we measure the current from VDD (connector p22) at nrf52840 DK, then it shows the correct current draw (around 5.1uA). In our custom board, the voltage is supplied to VDDH. We don't have an easy way to measure the current from VDD to the rest of circuit in the custom board.

We use the default LDO inside nrf52840 on the custom board. Could the LDO has the leak current of 5uA?

BTW, we measured VDD at the custom board and it shows 3.0v. VDDH is at 3.8v. We did not set the voltage register for VDD. VDD should have a default output of 1.8V. Why VDD is 3.0V instead?