nRF52840 matching network

[Benoît]

Hello,

I'm confused regarding the nRF82840 matching network found in the datasheet and dev kit. Is the Pi-filter composed of C3-L1-C4 the 50ohm matching network or should I add another matching network after this one ?

I ask the question because in the nRF52838 dev kit (pca20020) there is a L-filter followed by a T-filter on the RF track. So is the Pi-filter of the 52840 the equivalent of the L-filter of the 52832 or not ?

Thanks for your answer.

[Jørn]

Hello Benoît

Yes the pi filter of the nRF52840 performs the same job as the L filter of the nRF52832. There are differences between the 52840 and the 52832 so a different matching network is needed. So at the node called RF in the reference schematics you would have a 50 Ohm environment.

On the nRF52832 DK (Do you mean pca10040?) C3 and L1 matches the chip to 50 Ohm, and C15 matches the monopole trace-antenna to 50 Ohm. If a different antenna is used it may be necessary to use a pi network to match the antenna to 50 Ohm.

On the nRF52840 DK C3, L1 and C4 matches the chip to 50 Ohm, and C21 matches the antenna to 50 Ohm.

Best regards

Jørn Frøysa