NRX0 Datasheet, PDF (6/8 Pages) Radiometrix Ltd – 27MHz HF Narrow Band FM TX & RX

Applications information
Power supply requirements
Both modules have built-in regulators which deliver a constant 2.8V (4V in 50mW and 100mW version) to
the module circuitry when the external supply voltage is 2.9V or greater (4.1V in 50mW and 100mW
version), with 40dB or more of supply ripple rejection. This ensures constant performance up to the
maximum permitted rail, and removes the need for external supply decoupling except in cases where the
supply rail is extremely poor (ripple/noise content >100mV_pk-pk).
Continuous operation of 100mW version above 9V supply is not recommended.
The Enable pin allows the TX module to be turned on or off under 3V logic control with a constant DC supply
to the Vcc pin. The module current in power-down mode is less than 1µA.
The Enable pin should be tied directly to the Vcc pin if this facility is not required.
NTX0 modulation requirements
The module is factory-set to produce the specified FM deviation with a TXD input to pin 7 of 3V amplitude,
i.e. 0V “low”, 3V “high
If the data input level is greater than 3V, a resistor must be added in series with the TXD input to limit the
modulating input voltage to a maximum of 3V on pin 7. TXD input resistance is 100kΩ to ground, giving
typical required resistor values as follows:
Vcc
≤3V
3.3V
5V
9V
Series resistor
-
10 kΩ
68kΩ
220kΩ
NRX0 Received Signal Strength Indicator (RSSI)
The NRX0 receiver incorporates a wide range RSSI which measures the strength of an incoming signal over
a range of 55dB or more. This allows assessment of link quality and available margin and is useful when
performing range tests.
The output on pin 3 of the module has a standing DC bias of <0.5V with no signal, rising to 2V at maximum
indication.
Typical RSSI characteristic is as shown below:
Fig.6: Typical RSSI response curve
Radiometrix Ltd.,
NTX0/NRX0 data sheet
Page 6