Question: What are the recommendations for a PCB Layout for WUSB-NL?
- RF path: Adhere closely to the recommended reference design circuit (Refer TRM, FIGURE-3.1)
- Clock traces: Keep the quartz crystal traces simple and direct. The self-bias resistor should be close to the XTALi and XTALo pins. The oscillation loop, consisting of the series resistor and crystal, should be a simple, small loop. The crystal-loading capacitors should be near the crystal. The ground connection to these capacitors must be good, clean, and quiet. This prevents noise from being injected into the oscillator. It is best to have one ground plane for the entire RF section. Do not keep any unwanted trace below the crystal. The crystal and the associated components should be kept as close as possible to the IC pins (XTALOUT and XTALIN) to keep stray capacitance as minimum.
- Power distribution and decoupling: Capacitors should be located near the VDD pins, as shown in Typical Application on page 13 of the WUSB-NL TRM.
- Antenna placement: When using an antenna, follow the manufacturer's recommendation regarding layout.
- Digital interface: The digital interface should be routed with a solid ground reference, to have a good return path you need a good grounding between RF and MCU that can help reduce noise 'seen' at the antenna, thus improving performance.