Single ground is recommended: SGND. A multilayer such as 4 layers board is recommended so that one solid SGND is dedicated for return current path, referred to the layout example.
Apply multiple different capacitors for different frequency range on decoupling circuits. Each capacitor has different ESL, Capacitance and ESR, and they have different frequency response.
Avoid long traces close to radiation components, and place them into an internal layer, and it is preferred to have grounding shield.
Analog circuits and digital circuits should have separate return to ground; although with a single plane, still try to avoid mixing analog current and digital current.
Do not use a ferrite bead or larger than 3-Ω resistor to connect between V33A and V33D.
Both 3.3VD and 3.3VA should have local decoupling capacitors close to the device power pins, add vias to connect decoupling caps directly to SGND.
Avoid negative current/negative voltage on all pins, so Schottky clamping diodes may be needed to limit the voltage; avoid more than 3.8 V or less than –0.3 V voltage spikes on all pins; add Schottky diodes on the pins which could have voltage spikes during surge test; be aware that a Schottky has relatively higher leakage current, which can affect the voltage sensing at high temperature.
If V33 slew rate is less than 2.5 V/ms the RESET pin should have a 2.21-kΩ resistor between the reset pin and V33D and a 2.2-µF capacitor from RESET to ground. For more details please refer to the UCD3138 Family - Practical Design Guideline. This capacitor must be located close to the device RESET pin.
RSVD (Pin 61) should be connected to BP18 through 1-kΩ resistor.
Configure unused GPIO pins to be inputs or connect them to the ground (DGND or SGND); when an external pull-up resistor is used for GPIO, the pull-up resistor needs to be 1 kΩ or higher.