Current consumption of the nRF52 Development Board at 1,8V

[Heiner]

Hello,

at 3.3V the current consumption of my development kit is about 21.5 µA.

Due to the law of energy conservation, I would expect the current at 1.8V to be a little bit higher, somewhere around 39.4 µA.

But in fact the current consumption raised to an enormous 870 µA. Which I can not reasonably explain, since there have not been any changes in software.

First, I tried to disable the DC/DC converter, which barley had an effect on the issue.

Then I looked at the schematic and actually cut SB_9, in effort to only power the nRF. 

 

This helped somewhat, as the current is now only at 130 µA.

But I still can't quite understand what is causing the rise in current consumption.

Is this a behavior of the development board (and maybe the MCU used for debugging) or is this behavior caused by the nRF52832?

Best,

Heiner

[haakonsh]

It's the DK and it's power supply. The nRF52 itself will behave just as you predict, a slightly higher current consumption due to the law of energy conservation and the lower efficiency of the DCDC converter at 1.8V. 

[Heiner]

Hi Haakonsh, 

thank you for the quick answer.

My guess was also that the DC/DC is less efficient at 1.8V, but not this much.

I'll just estimate the runtime with the power I measured at 3.3V then.

Do you know what is causing the current draw in particular? Is it the MCU used for debugging?

Best,

Heiner

[haakonsh]

Heiner said:

I'll just estimate the runtime with the power I measured at 3.3V then.

 The efficiency of the DCDC converter probably drops by 5% or something, so add that to your power estimation. 

Heiner said:

Do you know what is causing the current draw in particular? Is it the MCU used for debugging?

 The debugger MCU, power supply circuits for buttons and leds, the on-board flash, etc. 

The DK is not really intended to be run at 1.8V.

[Heiner]

haakonsh said:

The DK is not really intended to be run at 1.8V

That makes sense.

Thank you for the detailed description.