AN3206

Reference design

Doc ID 17406 Rev 3

7/14

Figure 3.

STM32W Ceramic Balun matching network

Figure 4 shows a PCB layout (layer 1). It is important that the PCB designer notice the

routes between the STM32W and the balun. ST recommends the use of an 0603 inductor to

allow ample space for the traces to go to the balun first with deterministic lengths. Trace

inductance between the inductor and balun is then absorbed into the total shunt inductance,

so it may be predictably offset by reducing the physical component value. The tuned value

on the reference design came out to be 3.3 nH.

Figure 4.

Layer 1 except showing the balun routes

The PCB designer has the option to route the traces to the inductor first and the balun

second, but this has the effect of moving the components further away from the STM32W.