ER400TRS Datasheet, PDF (5/7 Pages) List of Unclassifed Manufacturers – LPRS Prelimina ry Data Sheet

LPRS Prelimina ry Data Sheet
Easy -Radio ER400TRS Transceiver
ready to receive (default) or transmit. It would normally be left in this powered state ready to receive
data.
4. During power up the Busy Output line goes high.
5. Contact the Sales Office for special ‘fast’ versions that can incorporate internal ‘duty cycling’ to
further reduce quiescent power consumption for battery powered applications.
6. Serial data rate up to 38.4k standard but 76.8k available on request.
Notes
RSSI Output
The transceiver has a built in RSSI (Received Signal Strength Indicator) that provides an analogue output
voltage that is inversely proportional to the RF energy present within the pass band of the receiver. It ranges
from 0 Volt (maximum signal, –50dBm) to 1.2 Volts (minimum signal, -105bBm) and has a slope of
approximately 50dB/Volt. This analogue output signal should only be connected to a high impedance load
(>100k Ohms) and can be used to provide a measure of the signal strength and any interfering signals
(noise) within band during the installation and operation of systems.
433MHz
1.3
1.2
1.1
1
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
-105 -100 -95 -90 -85 -80 -75 -70 -65 -60 -55 -50
dBm
PCB Layout
Figure 4 RSSI Output
The Ground (0 Volt) pins of the transceiver should be connected to a substantial ground plane (large area of
PCB copper) connected to 0 Volt. It is suggested that a double-sided PCB be used with one layer being the
ground plane.
Power Supply
The supply used to power the transceiver should be ‘clean’ and free from ripple and noise (<20mV p-p total).
It is suggested that 100nF ceramic capacitors be used to de-couple the supply close to the power pins of the
transceiver. The use of ‘switch mode’ power supplies should be avoided as they can generate both
conducted and radiated high frequency noise that can be very difficult to eliminate. This noise may
considerably reduce the performance of any radio device that is connected or adjacent to the supply.
Antennas
The transceiver can be used with the various common types of antenna that match the 50 Ohm RF
Input/Output such as a monopole (whip), helical or PCB/Wire loop antennas.
Monopole antennas are resonant with a length corresponding to one quarter of the electrical wavelength
(λ/4). They are very easy to implement and can simply be a ‘piece of wire’ or PCB track which at 434MHz
should be 16.4 cms in length. This should be straight, in ‘free space’ (kept well away from all other circuitry)
and should be connected directly to the Antenna pin of the transceiver. If the antenna is remote it should be
connected via a 50 Ohm coaxial feeder cable or transmission line. A 50 Ohm transmission line can be
constructed on FR4 board material by using a 3mm wide PCB track over a ground plane. This should be
kept as short as possible.
Helical antennas are also resonant and generally chosen for their more compact dimensions. They are more
difficult to optimise than monopole antennas and are critical with regard to surrounding objects that can
Easy-Radio ER400TS-RS 1.3
Copyright LPRS 2002. Iss. 1-3 September 2003
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