User's Manual Part 2
11
XDL Micro Intergrator’s Guide
Electrical Considerations
Power supply
The transceiver has a power supply connection on pins 18, 23, 24, 25, 26, 27, and 28 of the
interface connector. If there is a potential for a ground path current loop due to incorrect
power application, Pacific Crest recommends that you insert a fusible link in the signal
ground to protect the transceiver.
The XDL Micro transceiver is designed to operate with an unregulated DC voltage level at
3.6 ±0.4V. The power supply must be capable of sourcing 2 A.
Data interface
The transceiver has one serial port. It is a data port that has a simple 3-wire CMOS
electrical interface with signals for transmitting data to, and receiving data from, the
transceiver, and for providing a reference ground for the Tx (pin 3) and Rx (pin 14) signals.
Note– Pacific Crest defines Tx and Rx as a DTE port. That is, an external device transmits
data to the radio modem’s Tx pin (pin 3) and receives data from the radio modem’s Rx pin
(pin 14).
CMOS input/output protection circuitry
The Tx signal terminates into a CMOS input port on the transceiver and should be driven
externally or pulled to ground through a 10 kΩ resistor. The absolute maximum voltage
applied to the Tx signal is -0.3 v to 3.3 V.
The Rx signal is CMOS outputs. Note that loading the RX signal increases the power
consumption of the transceiver and these should be limited to no more than 2.5 mA in
order to maintain performance across the temperature range.
CAUTION – Internal circuitry protects the inputs and outputs against damage caused by
high static voltages or electric fields. However, normal precautions are necessary to avoid
application of any voltage higher than the maximum-rated voltages.
NC pins
Pins 2, 4, 6, 8, 10, 12, 13, and 15 through 17 must be left with no connection.