AN4630 Datasheet, PDF (25/33 Pages) STMicroelectronics – PCB design guidelines for the BlueNRG and BlueNRG-MS devices

AN4630
Design recommendations when using
WLCSP34 package
Figure 20: WLCSP34 ground connection (INNER3 layer view)
To guarantee the RF performances with the DC-DC converter ON it is important to have an
effective filtering between VBAT1 and SMPS_GND pins. This filtering is obtained using
some filtering capacitors are shown in Figure 21: "Focus on power supply pins". The C6
and C8 capacitors between the VBAT1 and the SMPS_GND have to be put as close as
possible to the WLCSP. The width of the connection tracks has to be increased as much as
possible. The TOP layer or the INNER2 layer has to be used to route these tracks.
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