1. Are there any other resources than RTC/WDT requiring 32kHz LFCLK, not listed in Table 28 of nRF51422 PS (i.e. Radio)?
2. ANT stack requires LFCLK +-50ppm, so +-25ppm 16MHz XOSC should be sufficient, when using synthesized LFCLK/NRF_CLOCK_LFCLKSRC_SYNTH_250_PPM (+-33ppm). Or not?
Ole Morten writes (valid for nRF51822): In general, there should never be a reason to use this clock source, and you should always be able to use RC oscilator (not applicable together with ANT) instead of the synthesized clock.
I have two reasons: limited board space, 32kHz crystal + load capacitors costs. However I'd like a low consumption too.
3. So what's the approx. average current consumption increase when CPU (16MHz HFCLK, maybe 4,4mA/I_CPU,Flash NOT incl. 0,81mA/I_1V2XO16) + SPI (master @500kHz CLK, maybe 0,2mA) + S210 (1 ANT master transmit channel, broadcast @16Hz) is RUNning a) with LFCLK synthesized b) with LFCLK supplied from external 32kHz crystal?
Is that difference roughly equal to 0,8mA (always I_1V2XO16+I_SYNTH32k x I_X32k+some time I_1V2XO1)?
www.thisisant.com/.../ probably takes external 32kHz crystal into account:
nRF51422 - 1 ANT transmit channel, message rate 16Hz 323uA avg, 3uA base
There is apparently no way, how to slow down HFCLK 16MHz to reduce current consumption during processing. Only CPU's switching between RUN and SLEEP with Constant Latency (16MHz XOSC always running) or Low Power sub modes in system ON.
Thanks for answers