Current consumption difference - nrf5340 running at 128MHz vs 64MHz

RE: Current consumption difference - nrf5340 running at 128MHz vs 64MHz

Stian Røed Hafskjold — Fri, 26 Aug 2022 13:09:11 GMT

Hi, there's some more information here: https://infocenter.nordicsemi.com/topic/ps_nrf5340/chapters/pmu/doc/pmu.html?cp=3_0_0_3_0#topic

So basically what you need to do is to configure the clock to 64MHz before the CPU goes to sleep. The easiest option, if you want to run the CPU at 128MHz during CPU intensive tasks, algorithms, etc, is to toggle the frequency before and after these specific algorithms. If you always want 128MHz when the CPU is running, the best option is probably to modify the idle thread to toggle back to 64MHz before WFE.

RE: Current consumption difference - nrf5340 running at 128MHz vs 64MHz

sshenoy105 — Tue, 23 Aug 2022 17:51:12 GMT

thanks for the response.. what are our options given this is going to affect our battery life significantly ? and running at 64MHz is not really the option we want to use

RE: Current consumption difference - nrf5340 running at 128MHz vs 64MHz

Stian Røed Hafskjold — Tue, 23 Aug 2022 15:02:42 GMT

I was just looking through the electrical specs and found that this is in fact a known issue:

I_{ON_IDLE3}

System ON, wake on any event, power-fail comparator enabled

1.3

I_{ON_IDLE3,128MHz}

System ON, wake on any event, power-fail comparator enabled, clock=HFINT128M

785

https://infocenter.nordicsemi.com/topic/ps_nrf5340/chapters/current_consumption/doc/current_consumption.html?cp=3_0_0_3_3_0_0#unique_2095571962

I'm also getting around 700 uA when enabling 128MHz, so I would say that your 400 uA base current is actually lower than expected. It could be due to chip to chip variation, or different voltage or regulator settings, etc.

RE: Current consumption difference - nrf5340 running at 128MHz vs 64MHz

Stian Røed Hafskjold — Tue, 23 Aug 2022 14:57:20 GMT

Hi, I'm able to reproduce what you are seeing here. It looks to me like the clock tree is always on when the clock source is configured to be 128MHz. I will have to run this through the HW designers, and see if this is intentional or not, and if there is a workaround. Will keep you updated.

Best regards,
Stian