When using an external 32.768KHz crystal I am unable to meet the 200mV to 1000mV peak to peak amplitude spec in the data sheet. Will this be a problem?

Answer

There are multiple low frequency clock source options that can be used on the BL5340 module:

·        The Internal 32.768 kHz RC oscillator (LFRC)

·        LFXO (32.768kHz crystal oscillator)

·        Low frequency (32.768 kHz) external source

o   A low swing clock

o   A rail-to-rail clock

·        LFSYNTH (32.768kHz Synthesized clock) from HFCLK (LFSYNTH)

The datasheet provides information showing peak-to-peak amplitude for external low swing clock.

Peak to Peak amplitude of 200mV to 1000mV is required when using a low swing, low frequency single rail oscillator. This is sometimes misinterpreted for cases using an external 32.768KHz crystal oscillator. An external 32.768KHz oscillator will typically have a swing of less than 200mV.