11.1.3 Power Management Unit

The ATWILC3000A contains an on-chip switching regulator, which regulates the VBAT supply for supplying to the rest of the device. It is crucial to place and route the components associated with this circuit correctly to ensure proper operation and especially to reduce any radiated noise, which can be picked up by the antenna and can severely reduce the receiver sensitivity. The external components for the PMU consist of two inductors, L5 = 15 nH and L1 = 1 μH and a capacitor, C10 = 10 μF. These components must be placed as close as possible to ATWILC3000A pin #25. The smaller inductor, L5, must be placed closest to pin #25. Current will flow from pin #25, through L5, then L1, and then through C10 to ground and back to the center ground paddle of the ATWILC3000A package.

Place components to have a current loop that is as small as possible. Make sure that there is a ground via to the inner ground plane right next to the ground pin of C10. The ground return path must be extremely low inductance. Failure to provide a short, heavy ground return between the capacitor and the ATWILC3000A ground pad will result in incorrect operation of the on-chip switching regulator. The following figure shows an example placement and routing of these components. In the following figure, the trace which creates the loop is highlighted in red.