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RF83//RF83C/RF83L/RF83CL ASK/OOK Receiver V2.0

 

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14.2. Shutdown Function

Duty-cycled operation of the RF83/RF83C (often referred to as polling) is achieved by turning the

RF83/FR83C on and off via the SHUT pin. The shutdown function is controlled by a logic state applied to

the SHUT pin. When VSHUT is high, the device goes into low-power standby mode. This pin is pulled high

internally; it must be externally pulled low to enable the receiver.

14.3. Power Supply Bypass Capacitors

VDDBB and VDDRF should be connected together directly at the IC pins. Supply bypass capacitors are

strongly recommended. They should be connected to VDDBB and VDDRF and should have the shortest

possible lead lengths. For best performance, connect VSSRF to VSSBB at the power supply only (that is,

14.4. Increasing Selectivity with an Optional BandPass Filter

For applications located in high ambient noise environments, a fixed value band-pass network may be

connected between the ANT pin and VSSRF to provide additional receive selectivity and input overload

protection. A minimum input configuration is included in figure 2a. it provides some filtering and

necessary overload protection.

14.5. Data Squelching

During quiet periods (no signal) the data output (DO pin) transitions randomly with noise. Most decoders

can discriminate between this random noise and actual data but for some system it does present a problem.

There are three possible approaches to reducing this output noise:

1) Analog squelch to raise the demodulator threshold

2) Digital squelch to disable the output when data is not present

3) Output filter to filter the (high frequency) noise glitches on the data output pin.

The simplest solution is add analog squelch by introducing a small offset, or squelch voltage, on the CTH

pin so that noise does not trigger the internal comparator. Usually 20mV to 30mV is sufficient, and may be

desired offset polarity. Since the RF83/RF83C has receiver AGC noise at the internal comparator input is

always the same, set by the AGC. The squelch offset requirement does not change as the local noise strength

changes from installation to installation. Introducing squelch will reduce sensitivity and also reduce range.

Only introduce an amount of offset sufficient to quiet the output. Typical squelch resistor values range from

6.8MΩ to 10MΩ.

14.6. Wake-Up Function

For RF83, The WAKEB output signal can be used to reduce system power consumption by enabling the

rest of a system when an RF signal is present. The WAKEB is an output logic signal which goes active low

when the IC detects a constant RF carrier. The wake-up function is unavailable when the IC is in shutdown

mode.