nRF51822_xxAC low power mode verification

[premji]

Hi,

Now as I want to ensure low power mode with minimum hardware and firmware, I have written very small code to check it. Simply, I have initialized timer only and go to system-on low power mode. With this it gives me 300 uA. But if even I comment out timer-init, it gives me 85 uA current consumption.

So my main query is why only timer run gives 215 uA more consumption ??

Please go through my simple attached code and suggest me.main.c

Thanks.

[Stefan Birnir Sverrisson]

Hi

I think I can explain this behavior.

When you enable the 16MHz crystal but do not use the TIMER peripheral, the crystal will stay in standby mode since no peripheral requires (uses) the crystal.

When you enable the timer the crystal is required in 1MHz mode since you have the TIMER prescaler = 9, which adds according to the specification: I_X16M,1M - I_STBY,X16M = 250-25=225uA, see the nRF51822_PS v3.1 table 22

Additionally, when you initialize the TIMER peripheral, it will typically add 4uA in 1MHz mode, see the nRF51822_PS v3.1 table 52 .

So the current consumption increase you should see according to specification should be 225+4=229uA. The current consumption numbers given in the specification are typical numbers, so it might not be that accurate anyway.

If you set the TIMER prescaler = 0, then the crystal and timer will be in normal mode and you will see higher current consumption.

[premji]

Hi Stefan,

Thanks for response,

Now I have taken RTC timer instead of normal timer, so I reduced around 250 uA.

[Stefan Birnir Sverrisson]

That is great. RTC is much better than TIMER in terms of current consumption.