Consumer Microcircuits Limited FX614P3, FX614D4 Datasheet

CML Semiconductor Products
Bell 202 Compatible Modem FX614
1997 Consumer Microcircuits Limited
D/614/4 October 1997
Advance Information
1.0 Features
•• 1200bits/sec 1/2 Duplex Bell 202 compatible Modem with:
150bits/sec Back Channel
•• Optional 1200bits/sec Data Retiming Facility
•• 3.0 to 5.5V Supply; 1.0mA at 3V
'Zero-Power' Mode; 1
µµA
•• Optional Line Equalisation
•• -40°C to +85°C Operating
Temperature
•• 16-pin SOIC and DIL Packages
•• 3.58MHz Xtal/Clock Rate
1.1 Brief Description
The FX614 is a low power CMOS integrated circuit for the reception or transmission of asynchronous 1200bits/sec data and is suitable for use in Bell 202 type systems. It is also capable of generating the 5bits/sec or 150bits/sec 'back channel'.
The device incorporates an optional Tx and Rx data retiming function that removes the need for a UART in the associated
µC when operating at 1200bits/sec. An optional line equaliser is incorporated into the receive path,
this is controlled by an external logic level. The FX614 may be used in a wide range of telephone telemetry systems. With a low operating voltage of
3.0V, a very low current 'sleep' mode (1
µA) and an operating current of 1mA the device is ideal for portable,
terminal and line powered applications. A 3.58MHz standard Xtal/Clock rate is required and the device operates from a 3.0V to 5.5V supply. Both SOIC (D4) and Plastic DIL (P3) 16-pin package types are available.
Bell 202 Compatible Modem FX614
1997 Consumer Microcircuits Limited 2 D/614/4
CONTENTS
Section Page
1.0 Features ......................................................................................................1
1.1 Brief Description.........................................................................................1
1.2 Block Diagram ............................................................................................3
1.3 Signal List...................................................................................................3
1.4 External Components.................................................................................5
1.5 General Description....................................................................................5
1.5.1 Xtal Osc and Clock Dividers.......................................................5
1.5.2 Mode Control Logic ....................................................................6
1.5.3 Rx Input Amplifier.......................................................................6
1.5.4 Receive Filter and Equaliser.......................................................6
1.5.5 Energy Detector ..........................................................................7
1.5.6 FSK Demodulator ................................................................ ........7
1.5.7 FSK Modulator and Transmit Filter ................................ ............7
1.5.8 Rx Data Retiming ........................................................................9
1.5.9 Tx Data Retiming ................................................................ .......10
1.6 Application Notes.....................................................................................12
1.6.1 Line Interface.............................................................................12
1.7 Performance Specification.......................................................................13
1.7.1 Electrical Performance..............................................................13
1.7.2 Packaging..................................................................................16
Bell 202 Compatible Modem FX614
1997 Consumer Microcircuits Limited 3 D/614/4
1.2 Block Diagram
Figure 1 Block Diagram
1.3 Signal List
FX614
D4/P3
Signal Description
Pin No. Name Type
1 XTALN O/P The output of the on-chip Xtal oscillator inverter. 2 XTAL/CLOCK I/P The input to the on-chip Xtal oscillator inverter. 3 M0 I/P A logic level input for setting the mode of the
device. See section 1.5.2.
4 M1 I/P A logic level input for setting the mode of the
device. See section 1.5.2. 5 RXIN I/P Input to the Rx input amplifier. 6 RXFB O/P Output of the Rx input amplifier, and the input to
the Rx filter. 7 TXOP O/P The output of the FSK generator.
8 V
SS
Power The negative supply rail (ground).
Bell 202 Compatible Modem FX614
1997 Consumer Microcircuits Limited 4 D/614/4
FX614
D4/P3
Signal Description
Pin No. Name Type
9 V
BIAS
O/P Internally generated bias voltage, held at VDD/2
when the device is not in 'Zero-Power' mode.
Should be decoupled to VSS by a capacitor
mounted close to the device pins.
10 RXEQ I/P A logic level input for enabling/disabling the
equaliser in the receive filter. See section 1.5.4.
11 TXD I/P A logic level input for either the raw input to the
FSK Modulator or data to be re-timed depending
on the state of the M0, M1 and CLK inputs. See
section 1.5.9.
12 CLK I/P A logic level input which may be used to clock
data bits in or out of the FSK Data Retiming
block.
13 RXD O/P A logic level output carrying either the raw
output of the FSK Demodulator or re-timed
characters depending on the state of the M0, M1
and CLK inputs. See section 1.5.8.
14 DET O/P A logic level output of the on-chip Energy Detect
circuit.
15 RDYN O/P "Ready for data transfer" output of the on-chip
data retiming circuit. This open-drain active low
output may be used as an Interrupt
Request/Wake-up input to the associated
µC.
An external pull-up resistor should be connected
between this output and VDD.
16 V
DD
Power The positive supply rail. Levels and thresholds
within the device are proportional to this voltage.
Should be decoupled to VSS by a capacitor
mounted close to the device pins.
Notes: I/P = Input
O/P = Output
This device is capable of detecting and decoding small amplitude signals. To achieve this V
DD
and V
BIAS
decoupling and protecting the receive path from extraneous in-band signals are very important. It is recommended that the decoupling capacitors are placed so that connections between them and the device pins are as short as practicable. A ground plane protecting the receive path will help attenuate interfering signals.
Bell 202 Compatible Modem FX614
1997 Consumer Microcircuits Limited 5 D/614/4
1.4 External Components
R1
100k
C1, C2 18pF
X1 3.579545MHz C3
0.1
µF
C4
0.1
µF
Resistors
±5%, capacitors ±10% unless otherwise stated.
Figure 2 Recommended External Components for Typical Application
1.5 General Description
1.5.1 Xtal Osc and Clock Dividers
Frequency and timing accuracy of the FX614 is determined by a 3.579545MHz clock present at the XTAL/CLOCK pin. This may be generated by the on-chip oscillator inverter using the external components C1, C2 and X1 of Figure 2, or may be supplied from an external source to the XTAL/CLOCK input. If supplied from an external source, C1, C2 and X1 should not be fitted.
The on-chip oscillator is turned off in the 'Zero-Power' mode. If the clock is provided by an external source which is not always running, then the 'Zero-Power' mode must be
set when the clock is not available. Failure to observe this rule may cause a significant rise in the supply current drawn by FX614 as well as generating undefined states of the RXD, DET and RDYN outputs.
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