Adverting event, current is big

[zcmm]

  Dear all  
          I use QFAB QFN48 schematic with internal LDO setup,but my board have not 32.768KHZ.

the Pre_processing current is big when in adverting .Why?

[Dave_couling]

I have seen something like this back when I worked with a CC2540. It was the DCDC circuit switching on, cause a fast voltage different and thus current rush. If you say you're not using the DCDC perhaps its related to RC Calibration? Though you should see peaks this high.

[Susheel Nuguru]

This is interesting, Agree with Dave's comment. Any updates from you zcmm?

[Dave_couling]

I have started seeing this issue with the rev 3 Silicon chips. I do not use an external LDO. I run in internal LDO mode. At the rising edge of pre-processing during any RF event I see 19.5mA current spikes. I haven't been able to determine root cause yet. Any update on this?

[Susheel Nuguru]

Only thing i can think of is the RC calibration like you mentioned, but that should not happen with every advertising event.

[Kenneth]

I expect this to be a short current spike of few us when internal regulators and internal circuitry power ON. This should easily be handled by adding 1uF to 4.7uF decoupling capacitor on VDD, the current may be high, but the time is very short. For instance the 47nF capacitor on DEC2 needs to be charged when powering ON, so you need some decoupling on VDD to handle this. If that doesn't work, please share the schematic so we can take a closer look.