Reference Manual

Table Of Contents

Design notes Power supply design

Digi XBee® 3 RF Module Hardware Reference Manual

Power supply design

A poor power supply can lead to poor device performance, especially if you do not keep the supply

voltage within tolerance or if it is excessively noisy. To help reduce noise, place a 1.0 µF and 8.2 pF

capacitor as near as possible to the VCC connection on the XBee 3 (pad 2 for micro and surface-

mount, and pin 1 for through-hole). Adding a 10 µF decoupling capacitor is also recommended. If you

are using a switching regulator for the power supply, switch the frequencies above 500 kHz. Limit the

power supply ripple to a maximum 50 mV peak to peak. For best results, place the lower capacitance

capacitors closest to the XBee 3 device.

Note XBee 3 parts with an early revision of the microcontroller unit (MCU) may experience an issue

recovering from brownouts under rare conditions. See Brownout issue for details on how to avoid this

issue.

Board layout

We design XBee 3 modules to be self-sufficient and have minimal sensitivity to nearby processors,

crystals or other printed circuit board (PCB) components. Keep power and ground traces thicker than

signal traces and make sure that they are able to comfortably support the maximum current

specifications. There are no other special PCB design considerations to integrate XBee 3 modules,

with the exception of antennas.

Antenna performance

Antenna location is important for optimal performance. The following suggestions help you achieve

optimal antenna performance. Point the antenna up vertically (upright). Antennas radiate and receive

the best signal perpendicular to the direction they point, so a vertical antenna's omnidirectional

radiation pattern is strongest across the horizon.

Position the antennas away from metal objects whenever possible. Metal objects between the

transmitter and receiver can block the radiation path or reduce the transmission distance. Objects

that are often overlooked include:

n Metal poles

n Metal studs

n Structure beams

n Concrete, which is usually reinforced with metal rods

If you place the device inside a metal enclosure, use an external antenna. Common objects that have

metal enclosures include:

n Vehicles

n Elevators

n Ventilation ducts

n Refrigerators

n Microwave ovens

n Batteries

n Tall electrolytic capacitors

Use the following additional guidelines for optimal antenna performance: