User's Manual Part 2

12
XDL Micro Intergrator’s Guide
Power down pin
Pin 29 is the active low pin used to turn off power to the XDL Micro transceiver. The VIH
(Voltage Input High) minimum is 1.2 V and VIL (Voltage Input Low) maximum is 0.3 V. It
has a 10 K pull-up resistor to VCC. You can leave it unconnected (NC) if you do not want
to turn off the XDL Micro transceiver.
Error codes
The transceiver performs a variety of start-up and run-time tests to ensure optimal
operation. Tests include environmental as well as electrical measurements designed to
avoid damage to the unit while maintaining adequate operation.
A 50 Ω impedance coaxial MMCX style RF connector is provided to attach to an external
antenna system. The MMCX connector offers a positive friction locking mechanism that
is very reliable. In some circumstances it may be required to provide a physical stop to
prevent the MMCX plug from becoming disconnected due to extreme shock or vibration.
The transceiver requires an antenna and feed cable system that is impedance-matched
to 50 Ω. Pacific Crest recommends that you use a high-quality RG-178 or equivalent
coaxial cable for internal wiring of the RF signal from the MMCX connector to the panel
connector. Pacific Crest also recommends you select an antenna that has a low VSWR
(Voltage Standing Wave Ratio) (less than 1.5:1) and which is tuned for operation in the
band of the XDL Micro transceiver.
CAUTION – Incorrect impedance matching of the antenna, connectors, or cable degrades the
performance of the transceiver.
Shielding considerations
The transceiver is designed to operate in proximity to noise-generating circuitry.
However, certain radiated or conducted frequencies may degrade the performance of
the transceiver or make it inoperable. When possible, provide well-grounded shielding
between the transceiver and radiating circuits, such as power supplies, voltage-controlled
oscillators, and crystal oscillators.