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CML

FX469 Datasheet Preview

FX469 Datasheet

1200/2400/4800 Baud FFSK Modem

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CML Semiconductor Products
PRODUCT INFORMATION
FX469 1200/2400/4800 Baud
FFSK Modem
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
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 DATA I/P
Tx ENABLE
Tx GENERATOR Tx FILTER
CLOCK RATE
XTAL/CLOCK
XTAL
CLOCK
OSCILLATOR
1200/2400 BAUD SELECT
4800 BAUD SELECT
Rx ENABLE
Rx SIGNAL I/P
Rx FILTER
DIVIDER
f .. n
LIMITER
RETRIGGERABLE
MONOSTABLE
DIGITAL
FILTER
DATA
FILTER
Tx SIGNAL O/P
Tx SYNC O/P
VDD
V BIAS
VSS
LIMITER
BANDPASS O/P
UNCLOCKED
DATA O/P
RECTIFIER
NOISE FILTER RECTIFIER
Fig.1 Functional Block Diagram
DIGITAL
PLL
DATA
LATCH
CLOCKED
DATA O/P
Rx SYNC O/P
S/N
COMPARATOR
CARRIER DETECT TIME CONSTANT
CARRIER DETECT O/P
FX469
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.
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.
1




CML

FX469 Datasheet Preview

FX469 Datasheet

1200/2400/4800 Baud FFSK Modem

No Preview Available !

Pin Number Function
FX469
DW LG/LS J/P6
1 1 1 Xtal/Clock : The input to the on-chip inverter, for use with either a 1.008MHz or a 4.032MHz
Xtal or external clock. Clock frequency selection is by the “Clock Rate” input pin. The
selection of this frequency will affect the operational Data Rate of this device. Refer to Baud
Selection information on the next page. Operation of any CML microcircuit without a Xtal or
clock input may cause device damage. To minimise damage in the event of a Xtal/drive
failure. it is recommended that the power rail (VDD) is fitted with a current limiting device
(resistor or fast-reaction fuse).
2 2 2 XtalN : Output of the on-chip inverter.
3 3 3 Tx Sync O/P : A squarewave, produced on-chip, to synchronize the input of logic data and
transmission of the FFSK signal (See Figure 4).
4 5 5 Tx Signal O/P : When the transmitter is enabled, this pin outputs the (140-step pseudo
sinewave) FFSK signal (See Figure 4).
With the transmitter disabled, this output is set to a high-impedance state.
5 7 6 Tx Data I/P : Serial logic data to be transmitted is input to this pin.
6 8 7 Tx EnableN : A logic ‘0’ will enable the transmitter (See Figure 4). A logic ‘1’ at this input will
put the transmitter into powersave whilst forcing “Tx Sync Out” to a logic ‘1’ and “Tx Signal
Out” to a high-impedance state. This pin is internally pulled to VDD.
7 9 8 Bandpass O/P : The output of the Rx Bandpass Filter. This output impedance is typically
10kW and may require buffering prior to use.
8 10 9 Rx Enable : The control of the Rx function. The control of other outputs is given below.
Rx Enable = Rx Function Clock Data O/P Carrier Detect Rx Sync Out
“1”
= Enabled
Enabled
Enabled
Enabled
“0” = Powersave “0”
“0” 1” or “0”
9
11 10
V : The output of the on-chip analogue bias circuitry. Held internally at V /2, this pin
BIAS
DD
should be decoupled to VSS by a capacitor (C2). (See Figure 2.
This bias voltage is maintained under all powersave conditions.
10 12 11 VSS: Negative supply rail (GND).
2


Part Number FX469
Description 1200/2400/4800 Baud FFSK Modem
Maker CML
Total Page 10 Pages
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