User's Manual Part 1

TDL 450i Intergrator’s Guide 13
Electrical Considerations
Power Supply
The TDL 450i transceiver has a power supply connection on Pin 18 and Pins 23 to 28 of the interface
connector. Pins 1, 5,7, 9,30 and Pins 19 to 22 are connections to both power ground and serial interface
signal grounds. Note that these pins are tied to a common point on the TDL 450i transceiver. If there is a
potential for a ground path current loop due to improper power application, we recommend a fusible link
be inserted in the signal ground to protect the TDL 450i transceiver.
TDL 450i transceiver modems are designed to operate with unregulated DC voltage levels between 3.6 and
4VDC. The power supply must be capable of sourcing 2A.
Data Interface
TDL 450i transceiver provides one data port, which has a simple 3-wire CMOS electrical interface with
signals for transmitting data to and receiving data from the TDL 450i transceiver, and for providing a
reference ground for the TX (Pin 3) and RX (Pin 14) signals.
Note: We define TX and RX as a DTE port. In other words, 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 TDL 450i 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 signals are CMOS outputs. Note that loading the RX signals increases the power consumption of the
TDL 450i transceiver and these should be limited to no more than 2.5 mA each 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.