nrf52810 LFSYNT current consumption

[Erwin v. H.]

We are developing a bluetooth product that operates on a battery where every uA counts and I have a couple of questions about current consumption in System On Low Power mode without an external low speed crystal.

1) What is the current consumption of the LFSYNT clock for a nRF52810?

Is that the same as shown in the picture below (copied from the nRF52832 datasheet):

Or will this be higher or lower for a nRF52810?

2) Are these calculations also true for a nRF52810: Current-consumption?

3) If either the LFSYNT clock is used or the LFRC will they remain running in System On mode Low Power, and therefor increase the power consumption? 

Thanks in advance, 

Erwin

[ovrebekk]

Hi

Synthesizing the LF clock from the HF clock is very inefficient in terms of power consumption. In addition to the ~100uA drawn by the LF circuitry itself, you need to factor in the run current of the HF clock, which is even higher (typically 200-500uA, depending on the HF clock source and type). 

Are you sure it is LFSYNT you are considering, and not LFXO?

LFXO is the external LF clock option, which allows you to reduce the current draw significantly while also providing a highly accurate LF clock. 

You can use the system in system ON low power mode regardless of the LF source (LFRC, LFXO or LFSYNT), but even in the "low power" state the total power consumption will depend on which peripherals and modules you have enabled. Any peripheral that requires a high frequency clock source (such as the LFSYNT feature) will significantly increase the current consumption. 

Best regards
Torbjørn

[Erwin v. H.]

Dear Torbjørn

We where considering it (due to BOM) until we found out that the LFSYNT cost that much current extra on the nRF52832, can you confirm that this current consumption is also correct for a nRF52810?

 

What about my question  regarding the LFRC circuit, do the calculations mentioned in my original post (Current-consumption) also apply to a nRF52810? Again this is for our BOM a better option.

Best regards,

Erwin

[ovrebekk]

Hi Erwin

I can confirm that the nRF52810 has similar current consumption to the nRF52832, for all of the RC options (external, synt and RC). I will ask internally if we can update the nRF52810 specification to include this information. 

The nRF52810 should be very similar to the calculations you link to, yes. 

Best regards
Torbjørn