CML Semiconductor Products
PRODUCT INFORMATION
FX469
Features
Selectable Data Rates
1200, 2400 and 4800 Baud
Full-Duplex FFSK
Rx and Tx Bandpass Filters
Clock Recovery and Carrier
Detect Facilities
Rx and Tx Enable Functions
Tx GENERATOR
Tx DATA I/P
Tx ENABLE
CLOCK RATE
Tx FILTER
1200/2400/4800 Baud
FFSK Modem
Publication D/469/6 April 1998
Pin Selected Xtal/Clock Inputs
1.008MHz or 4.032MHz
Radio and General Applications
Data-Over-Radio
PMR and Cellular Signalling
Portable Data Terminals
Personal/Cordless Telephone
Tx SIGNAL O/P
Tx SYNC O/P
V
DD
XTAL/CLOCK
CLOCK
OSCILLATOR
XTAL
1200/2400 BAUD SELECT
4800 BAUD SELECT
BANDPASS O/P
Rx ENABLE
Rx SIGNAL I/P
Rx FILTER
LIMITER
RETRIGGERABLE
MONOSTABLE
DIGITAL
FILTER
DATA
FILTER
LIMITER
UNCLOCKED
DATA O/P
DIVIDER
f
..
V
BIAS
n
V
SS
FX469
RECTIFIER
DIGITAL
PLL
DATA
LATCH
CLOCKED
DATA O/P
Rx SYNC O/P
NOISE FILTER
RECTIFIER
S/N
COMPARATOR
CARRIER DETECT TIME CONSTANT
CARRIER DETECT O/P
Fig.1 Functional Block Diagram
Brief Description
The FX469 is a single-chip CMOS LSI circuit which
operates as a full-duplex pin-selectable 1200, 2400 or
4800 baud FFSK Modem. The mark and space
frequencies are 1200/1800, 1200/2400 and 2400/4800
Hz respectively. Tone frequencies are phase
continuous; transitions occur at the zero crossing point.
Employing a common Xtal oscillator with a choice of
two clock frequencies (1.008MHz or 4.032MHz) to
provide baud-rate, transmit frequencies, and Rx and Tx
synchronization, the transmitter and receiver operate
entirely independently including individual section
powersave functions.
The FX469 includes on chip circuitry for Carrier Detect
and Rx Clock recovery, both of which are made
available as output pins.
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Rx, Tx and Carrier Detect paths each contain a
bandpass filter to ensure the provision of optimum
signal conditions both in the modem and for the Tx
modulation circuitry.
The FX469 demonstrates a high sensitivity and
good bit-error-rate under adverse signal conditions;
the carrier detect time constant is set by an external
capacitor, whose value should be arranged as
required to further enhance this product's performance
in high noise environments.
This low-power device requires few external
components and is available in small outline plastic
(S.O.I.C) and cerdip DIL packages.
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