Optimizing power for NRF52

[Jong yoon lee]

Hello, I am developing an an system and I am at the stage of optimizing for power. I using NRF6707 ( Very helpful !!) to measure current.

I cut SB9 of NRF52 DK and have NRF6707 on top of it.

I have some questions regarding the result I have.

First, when I use the Online Power Profiler, I get about 11uA for advertising at 1s. However When I actually test it on the test board, I get about 29uA. Is this a reasonable result or am I not doing something currently.

Also, in SDk12 What does #define SAADC_CONFIG_LP_MODE 1 do exactly and Should I use this for high frequency application (samples 2 channels with 1k)

Lastly, when I use the NRF6707 to profile power is it taking account the peripharial devices I attach to it? So if I attach for say axdl345 and communicate with it through spi, does the NRF6707 take account of the current used in the chip as well?

Thanks

[Daniel Wang]

This is a custom board? Make sure to enable DCDC if you can.

[Jong yoon lee]

I am using the stock DK. Do I need to use DCDC in order to get the 11uA for advertisting?

[Sigurd]

Hi,

If you have enabled different peripherals, and are not using DCDC mode, 29 µA is a reasonable result. You can enable DCDC like this:

NRF_POWER->DCDCEN = 1;

Add this before you initialize the SoftDevice. You can also enable the DCDC after SoftDevice initializing by using the function sd_power_dcdc_mode_set().

The PPK measures the total power consumption, so when you enable different peripherals the total power consumption will increase. E.g. the SPI idle current is 1 µA, while the SPI run current is around 50µA.

SAADC_CONFIG_LP_MODE enables Low Power mode. The driver will use less power, but more interrupts are generated.

I also recommend you to read this current consumption guide, it's written for the nRF51, but the main principles are the same.