FM T
RANSMITTER
& R
ECEIVER
M
ODULES
. (2
ND
G
ENERATION
)
RX2 receiver:
FM-TX2-XXX
FM-RX2-XXX
fig. 3: RX2 block diagram
Pin description
RF in
(
pin 1)
50
Ω
RF input from the antenna,
it is DC isolate internally. (see
antenna section of RX2
applications note for suggested
antenna/feeds).
RF GND
(
pin 2)
RF ground pin, internally
connected to the module screen
and pin 4 (0V). This pin should
be connected to the RF return
path (e.g. coax braid, main PCB
ground plane etc.)
fig. 4: physical dimensions
CD
(
pin 3)
The Carrier Detect may be used to drive an external PNP transistor to obtain a logic
level carrier detect signal, see test circuit / applications note. If not required it should
be connected to pin 5 (Vcc).
0volt
(pin 4)
Supply ground connection, connected to pin 1 and screen.
Vcc
(pin 5)
+ve supply pin. +3.0V to +6.0V @ <17mA . The supply must be clean < 2mV
P-P
ripple. A
10
µ
F de-coupling capacitor and 10
Ω
series resistor is recommended if a clean supply is
not available.
AF
(pin 6)
This is a buffered and filtered analogue output from the FM demodulator. It has a
standing DC bias of 1.2V and 400mV
P-P
base band signal. It is useful as a test point or
to drive linear decoders. Load impedance should be > 2k
Ω
and < 100pF.
RXD
(pin 7)
This digital output from the internal data slicer is a squared version of the signal on
pin 6 (AF). It may be used to drive external decoders. The data is true data, i.e. as fed
to the transmitter. Load impedance should be > 1k
Ω
and < 1nF
DS000022
Rev D
July ‘99
©1999
REG No 277 4001, ENGLAND.
Page 3
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