10.2 Layout Example
In addition to the layout guidelines already given, here are some additional comments for this specific layout example
- The most critical part of the layout that the placement of the pull-up components (R37, R38, R39, and R40) is close to the pin for optimal output power.
- For this layout, most of the loop filter (C1_LF, C2_LF, C3_LF, R2_LF, R3_LF, and R4_LF) are on the back side of the board. However note that C4_LF is on the top side right next to the Vtune pin. In the event that this C4_LF capacitor would be open, it is recommended to move one of loop capacitors in this spot. For instance, if a 3rd order loop filter was used, technically C3_LF would be non-zero and C4_LF would be open. However, for this layout example that is designed for a 4th order loop filter, it would be optimal to make R3_LF = 0 ohm, C3_LF = open, and C4_LF to be whatever C3_LF would have been.