EWM-900-FDTC-HS Radiotronix, EWM-900-FDTC-HS Datasheet - Page 15

• Manufacturer Part Number: EWM-900-FDTC-HS
• Description: RF Modules & Development Tools Head Set
• Manufacturer: Radiotronix

Specifications of EWM-900-FDTC-HS

• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Other names: (HS) EWM-900-FDTC

EWM-900-FDTC Full Duplex Voice/Data Transceiver
Data Sheet
Applications Information
Figure 5 shows the schematic diagram of our evaluation board. All of the transceiver parameters
in the specification sheet were determined on this board.
Power Supply
The transceiver is designed to operate from a 3V DC power supply. Power is provided to the
transceiver on pin 16. This power supply should be noise-free. Noise on the power supply will
degrade the receiver sensitivity, thereby decreasing range.
Ground
It is important to have a good ground system for any wireless design. The ground plane serves as
a base reference for the operation of RF circuitry. All filters are referenced to ground. All
oscillators are referenced to ground. If the ground system design is bad, RF circuitry may not
function correctly. The results may be reduced performance or spurious emissions.
As a rule of thumb, it is best to use a solid fill ground plane to connect all of the ground pins of the
transceiver.
Transmitter Start-Up Time
The start-up time for the transmitter is determined mainly by the loop bandwidth of the PLL loop
filter. When the transmitter is enabled by setting the TXE bit in the mode register to a 1, it can
take up to 20mSec for the transmitter to be on-channel and ready to transmit information.
Transmitter Channel-Change Time
The channel change time for the transmitter is the time it takes for the transmitter to be locked
onto the new channel after programming the TX channel register. For a 1MHz jump, the channel
change time is 11mSec. For a 100kHz jump, the channel change time is 7 mSec.
Transmitter Audio/Data Input Requirements
The TXD/AUDIN pin is connected to the transmit VCO. Voltage changes on this pin will
frequency modulate the VCO.
The input impedance of this pin will vary from module to module as required to set the proper
frequency deviation. Therefore, the pin must be driven by a low impedance source. If the driving
circuit is digital, it must have a push-pull output. If the driving circuit is analog, the signal should
be buffered by an operational amplifier.
A 3V p-p signal present at this pin will result in a +/-25kHz frequency deviation.
There is a 150Hz high-pass response on this pin due to the TX PLL loop filter. Therefore, the
transmitter is not capable of transmitting DC voltage levels. The bandwidth of the signal used to
modulate the transmitter should be between 300Hz and 15kHz. For data applications, the baud
rate should be between 9600 bps and 19.2kbps.
EWM-900-FDTC Data Sheet
Page 11
Revision 1.2 - 2/11/2004