Question

What's the minimal BOM filtering for the EFR32 Series 1 Wireless Gecko?

Answer

Silicon Labs reference radio board designs typically use an extensive number of components for RF and VDD filtering to achieve the best possible RF performance at even the highest output power levels. However, a number of these elements can be eliminated from the design while still maintaining an acceptable RF performance. 

Minimal BOM VDD rail filtering:

- VREGVDD: 100nF; 10uF

- AVDD: 10nF; 10uF

- DVDD: 100nF

- IOVDD: 1uF

- DECOUPLE: 1uF

- RFVDD: 220nF

- PAVDD: 220nF

Depending on the RF carrier frequency the following additional filtering capacitors are recommended to be added to the RFVDD and PAVDD nets:

- 10pF for the 2.4GHz applications

- 56-100pF at the high bands below 1GHz (868-915MHz, typically)

- 220-470pF at the lower sub-GHz bands (169-470MHz) 

In the case of having the PA-, RF- and DVDD rails run from the internal on-chip DC-DC converter, the following series inductors (or ferrites) need to be added:

- 22nH on PAVDD at 2.4GHz

- 100-120nH on PA-, and RFVDD at the higher sub-GHz bands

- 220-470nH on PA-, and RFVDD at the lower sub-GHz bands

Additional details can be found in "AN933.1: EFR32 Series 1 Minimal BOM" application note.