Module test circuits
TX3A
1
2
3
Radiometrix
4
5
6
7
2kHz
2.5V
0V
RF out
50
Ω
TXD
Vcc
En
GND
Fig.5: TX3A test circuit
RX3A
1
2
3
Radiometrix
4
5
6
7
8
9
RXD
RF in
50
Ω
AF out
Vcc
RSSI
En
0V (GND)
Fig.6: RX3A test circuit
Applications information
Power supply requirements
Both modules incorporate a built-in regulator which delivers a constant 2.8V to the module
circuitry when the external supply voltage is 2.85V or greater, with 40dB or more of supply
ripple rejection. This ensures constant performance up to the maximum permitted supply rail
and removes the need for external supply decoupling except in cases where the supply rail is
extremely poor (ripple/noise content >0.1V
p-p
).
Note, however, that for supply voltages lower than 2.85V the regulator is effectively
inoperative and supply ripple rejection is considerably reduced. Under these conditions the
ripple/noise on the supply rail should be below 10mV
p-p
to avoid problems. If the quality of the
supply is in doubt, it is recommended that a 10µF low-ESR tantalum or similar capacitor be
added between the module supply pin (Vcc) and ground, together with a 10Ω series feed
resistor between the Vcc pin and the supply rail.
The Enable pin allows the module to be turned on or off under logic control with a constant
DC supply to the Vcc pin. The module current in power-down mode is less than 1µA.
NOTE:
If this facility is used, the logic control signal must have a slew rate of 40mV/µs or
more. Slew rates less than this value may cause erratic operation of the on-board regulator
and therefore the module itself.
Radiometrix Ltd, TX3A & RX3A Data Sheet
page 6
RADIOMETRIX [ RADIOMETRIX LTD ]
