CMX469AE2 [ETC]
MODEM ; MODEM\n
| 型号： | CMX469AE2 |
| 厂家： | 
ETC |
| 描述： | MODEM
|
| 文件： | 总16页 (文件大小：476K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
CMX469A
1200/2400/4800 Baud
FFSK/MSK Modem
D/469A/2 May 2001
Provisional Issue
Features
Applications
· Full-Duplex FFSK/MSK Modem with
· Data-Over Radio
Separate Rx and Tx Enable Functions
· Personal/Cordless Telephone
· Radio and General Applications
· Narrowband Coax Data Channels
· Two Way Radio (MPT1327) Signalling
· Portable Data Terminals
· Pin Selectable Data Rates:
1200, 2400 or 4800 Baud
· Pin Selectable Xtal/Clock Inputs:
1.008MHz or 4.032MHz
· Clock Recovery Facility
· Carrier Detect Facility
· Low Power Operation (2.0mA typ. at 3.0V)
1.1
Brief Description
The CMX469A is a single-chip CMOS LSI circuit which operates as a full-duplex 1200, 2400 or
4800 baud FFSK/MSK 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. A common Xtal oscillator with a choice of two clock frequencies (1.008MHz or
4.032MHz) provides baud-rate, transmit frequencies, and Rx and Tx synchronization.
The transmitter and receiver operate entirely independently, including the individual section
powersave functions. The CMX469A 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
contain bandpass filters to optimise signal conditions in each section of the modem. The
CMX469A demonstrates good sensitivity and bit-error-rate under adverse signal conditions. The
Carrier Detect time constant is set by an external capacitor, so that the product's performance
can be optimised in high noise environments. This low-power device operates from a single
supply between 2.7V and 5.5V, requires few external components and is available in a wide
variety of plastic packages.
ã 2001 Consumer Microcircuits Limited
1200/2400/4800 Baud FFSK/MSK Modem
CMX469A
CONTENTS
Section
Page
1.0
1.1
1.2
1.3
1.4
1.5
1.6
1.7
Features and Applications.......................................................................2
Brief Description .......................................................................................2
Block Diagram ...........................................................................................4
Signal List...................................................................................................5
External Components...............................................................................7
General Description..................................................................................8
Application Notes......................................................................................9
Performance Specification.....................................................................10
1.7.1 Electrical Performance..............................................................10
1.7.2 Packaging....................................................................................16
ã 2001 Consumer Microcircuits Limited
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D/469A/2
1200/2400/4800 Baud FFSK/MSK Modem
CMX469A
1.2
Block Diagram
Figure 1 Block Diagram
ã 2001 Consumer Microcircuits Limited
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D/469A/2
1200/2400/4800 Baud FFSK/MSK Modem
CMX469A
1.3
Signal List
CMX469A
E2
D3
P6
Signal
Description
Pin
No.
Pin
No.
Pin
No.
Name
Type
1
1
1
CLOCK/XTAL
I/P
The input to the on-chip inverter, for use with
either a 1.008MHz or a 4.032MHz Xtal or an
external clock. Clock frequency selection is by
means of the CLOCK RATE pin. This affects the
operational data rate of the device. Operation of
any CML microcircuit without a Xtal or clock
input may cause device damage.
2
3
2
3
2
3
XTALN
O/P The output of the on-chip inverter.
Tx SYNC O/P
O/P A squarewave, produced on-chip, to
synchronize the input of logic data and
transmission of the FFSK/MSK signal.
4
5
5
Tx SIGNAL
O/P
O/P When the transmitter is enabled, this pin outputs
the FFSK/MSK signal. With the transmitter
disabled, this pin is set to a high-impedance
state.
5
6
7
8
6
7
Tx DATA I/P
Tx ENABLEN
I/P
The serial logic data to be transmitted is input to
this pin.
I/P
A logic ‘0’ will enable the transmitter. A logic ‘1’ at
this input will put the transmitter into powersave
whilst forcing Tx SYNC OUTPUT to a logic ‘1’
and Tx SIGNAL OUTPUT to a high-impedance
state. This pin is internally pulled to VDD
.
7
9
8
BANDPASS
O/P
O/P The output of the Rx Bandpass Filter. This output
impedance is typically 10kW and may require
buffering prior to use.
8
9
10
11
9
Rx ENABLE
I/P
BI
The control of the Rx function
10
V
BIAS
The output of the on-chip analogue bias circuitry.
Held internally at VDD/2, this pin should be
decoupled to VSS by a capacitor (C2). This bias
voltage is maintained under all powersave
conditions.
10
11
12
13
11
12
V
PWR Negative supply rail (GND).
SS
UNCLOCKED
DATA O/P
O/P The recovered asynchronous serial data output
from the receiver.
12
14
13
CLOCKED
DATA O/P
O/P The recovered synchronous serial data output
from the receiver. Data is latched out by the
recovered clock, available at the Rx SYNC O/P.
ã 2001 Consumer Microcircuits Limited
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D/469A/2
1200/2400/4800 Baud FFSK/MSK Modem
CMX469A
CMX469A
D3
E2
P6
Signal
Description
Pin
No.
Pin
No.
Pin
No.
Name
Type
13
14
15
16
15
16
18
19
14
15
17
16
CARRIER
DETECT O/P
O/P When an FFSK/MSK signal is being received
this output is a logic ‘1’.
Rx SIGNAL I/P
Rx SYNC O/P
I/P
The FFSK/MSK signal input for the receiver. This
input should be coupled via a capacitor, C3.
O/P A flywheel squarewave output. This clock will
synchronize to incoming Rx FFSK/MSK data.
1200/2400
BAUD
SELECT
I/P
A logic ‘1’ on this pin selects the 1200 baud
option. Tone frequencies are: one cycle of
1200Hz represents a logic ‘1,’ one-and-a-half
cycles of 1800Hz represents a logic ‘0.’
A logic ‘0’ on this pin selects the 2400 baud
option. Tone frequencies are: one-half cycle of
1200Hz represents a logic ‘1,’ one cycle of
2400Hz represents a logic ‘0.’ This function is
also used, in part, to select the 4800 baud
option. This pin has an internal 1MW pullup
resistor.
17
20
18
4800 BAUD
SELECT
I/P
A logic ‘1’ on this pin combined with a logic ‘0’ on
the 1200/2400 BAUD SELECT pin will select the
4800 baud option (1MW pulldown resistor).
Tone frequencies are: one-half cycle of 2400Hz
represents a logic ‘1,’ one cycle of 4800Hz
represents a logic ‘0.’ Operation at 4800 baud is
only achieved by using a 4.032MHz Xtal or
clock.
18
19
20
21
22
24
19
20
CLOCK RATE
I/P
BI
A logic input to select and allow the use of either
a 1.008MHz or 4.032MHz Xtal/clock. Logic ‘1’ =
4.032MHz, logic ‘0’ = 1.008MHz. This input has
an internal pulldown resistor (1.008MHz).
CARRIER
DETECT TIME
CONSTANT
Part of the carrier detect integration function. The
value of C4 connected to this pin will affect the
carrier detect response time and hence noise
performance.
22
PWR Positive supply rail. A single 2.7 to 5.0 volt
supply is required. This pin should be decoupled
VDD
to VSS by a capacitor (C5).
4, 6,
4, 21
No internal connection, do not use.
17, 23
Notes:
I/P = Input
O/P = Output
BI = Bidirectional
PWR = Power
ã 2001 Consumer Microcircuits Limited
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D/469A/2
1200/2400/4800 Baud FFSK/MSK Modem
CMX469A
1.4
External Components
Component
Value
1.0MW
33.0pF
1.0µF
0.1µF
0.1µF
1.0µF
1.0µF
33.0pF
R1
C1
C2
C3
C4
C5
C6
C7
X1
1.008MHz
or
4.032MHz
Notes:
1. VBIAS may be decoupled to VSS and VDD using C2 and C6 when input signals are referenced to the VBIAS
pin. For input signals referenced to VSS, decouple VBIAS to VSS using C2 only.
2. The performance of the Carrier Detect function will be affected by the nature of the noise spectrum in the
received channel. The value of C4 determines the Carrier Detect Time Constant. A long time constant
results in improved noise immunity but increased response time. C4 may be varied to trade-off response
time for noise immunity.
3. A 4.032MHz Xtal/clock is required for 4800 Baud operation.
Figure 2 Recommended External Components
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1200/2400/4800 Baud FFSK/MSK Modem
CMX469A
1.5
General Description
The CMX469A has two sections, apart from the Xtal oscillator circuit and clock dividers. These
sections may be independently powersaved.
Transmitter
The transmitter is enabled by taking Tx EnableN low. Serial data applied to Tx Data Input is sampled
internally and an FFSK/MSK sequence is generated. After filtering, this is output at
Tx Signal O/P and the transmit clock derived from this signal is output at Tx Sync O/P.
Receiver
The receiver is enabled by taking Rx Enable high. The signal applied to Rx Signal I/P is filtered and
recovered as serial data from the Unclocked Data O/P. A flywheel synchroniser is used to extract a
clock from the recovered serial data stream. The clock is available at Rx Sync O/P and the retimed
serial data is available at Clocked Data O/P.
The integrated peak values of the Rx amplitude are compared with out-of-band noise levels and used
to make a signal-to-noise assessment, which is available at Carrier Detect O/P.
A Bandpass O/P is also available from the output of the first Rx filter stage, but will require buffering
before use.
ã 2001 Consumer Microcircuits Limited
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D/469A/2
1200/2400/4800 Baud FFSK/MSK Modem
CMX469A
1.6
Application Notes
Rx Enable
The control of the relevant outputs with reference to the Rx Enable input is described below:
Rx Enable
Rx Function
Enabled
Clock Data O/P
Enabled
‘0’
Carrier Detect O/P
Enabled
Rx Sync Out
‘1’
‘0’
Enabled
‘1’ or ‘0’
Powersave
‘1’ or ‘0’
After enabling the Receiver, a time of at least 8 bit periods plus 2ms should be allowed for the Carrier Detect
circuit to stabilise and give a valid output.
Operational Data Rate Configurations
Operational Data Rate Configurations are as described below:
Xtal/Clock
Frequency
1.008MHz
4.032MHz
Clock Rate
‘0’
‘1’
‘0’
‘0’
‘1’
‘1’
‘1’
‘0’
‘1’
‘0’
1200/2400
Select
4800 Select
Baud Rate
‘0’
‘0’
‘0’
‘0’
‘1’
1200
2400
1200
2400
4800
Test Set Up
Figure 3 Suggested CMX469A Test Set-Up
ã 2001 Consumer Microcircuits Limited
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D/469A/2
1200/2400/4800 Baud FFSK/MSK Modem
CMX469A
1.7
Performance Specification
1.7.1 Electrical Performance
Absolute Maximum Ratings
Exceeding these maximum ratings can result in damage to the device.
Min.
Max.
Units
Supply (V - V
Voltage on any pin to V
Current into or out of V and V pins
Current into or out of any other pin
)
-0.3
-0.3
-30
-20
7.0
V
V
mA
mA
DD
SS
V
DD
+ 0.3
SS
+30
+20
DD
SS
D3 Package
Total Allowable Power Dissipation at Tamb = 25°C
... Derating
Storage Temperature
Operating Temperature
Min.
Max.
800
13
+125
+85
Units
mW
mW/°C
°C
-55
-40
°C
E2 Package
Min.
Max.
320
5.3
+125
+85
Units
mW
mW/°C
°C
Total Allowable Power Dissipation at Tamb = 25°C
... Derating
Storage Temperature
-55
-40
Operating Temperature
°C
P6 Package
Min.
Max.
800
13
+125
+85
Units
mW
mW/°C
°C
Total Allowable Power Dissipation at Tamb = 25°C
... Derating
Storage Temperature
-55
-40
Operating Temperature
°C
ã 2001 Consumer Microcircuits Limited
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D/469A/2
1200/2400/4800 Baud FFSK/MSK Modem
CMX469A
Operating Limits
Correct operation of the device outside these limits is not implied.
Notes
Min.
2.7
Max.
5.5
Units
V
Supply (V - V
)
SS
DD
Operating Temperature
Xtal Frequency
-40
4.028
+85
4.036
°C
MHz
1
Note 1: A Xtal frequency of 1.008MHz (1200/2400 baud only) or 4.032MHz is required for correct
operation. A frequency tolerance of ±0.1% is recommended, but ultimately the tolerance selected will
depend upon system requirements.
Operating Characteristics
For the following conditions unless otherwise specified:
V
DD
= 2.7V at Tamb = 25°C and V = 3.0V to 5.5V at Tamb = - 40°C to +85°C,
DD
Xtal/Clock Frequency = 4.032MHz, Bit Rate = 1200 baud, Rx Input Level = 300mVrms.
Notes
Min.
Typ.
Max.
Units
Static Values
I
I
I
Rx Enabled, Tx Disabled (V
= 5.0V)
= 5.0V)
= 5.0V)
2
2
2
-
-
-
3.6
4.5
650
-
-
-
mA
mA
µA
DD
DD
DD
DD
DD
DD
Rx and Tx Enabled
Rx and Tx Disabled
(V
(V
I
I
I
Rx Enabled, Tx Disabled (V
= 3.0V)
= 3.0V)
= 3.0V)
2
2
2
-
-
-
1.5
2.0
300
-
-
-
mA
mA
µA
DD
DD
DD
DD
DD
DD
Rx and Tx Enabled
Rx and Tx Disabled
(V
(V
Logic ‘1’ Level
Logic ‘0’ Level
Digital Output Impedance
Analogue and Digital Input Impedance
1
1
70%
-
-
100
-
-
-
-
30%
-
V
V
kW
kW
kW
DD
DD
4.0
-
0.6
-
Tx Output Impedance (V
= 5.0V)
1.0
DD
Dynamic Values
Receiver
Signal Input Dynamic Range SNR = 50dB
Bit Error Rate at SNR = 12dB
1200 Baud
3, 4
4, 5
100
230
1000
mVrms
-
-
-
2.5
1.5
1.5
-
-
10-4
10-3
10-3
2400 Baud
4800 Baud
-
Bit Error Rate at SNR = 20dB
1200/2400/4800 Baud
Receiver Synchronization at SNR = 12dB
probability of bit 16 being correct
4, 5
7
-
-
<1.0
-
-
10-8
0.995
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D/469A/2
1200/2400/4800 Baud FFSK/MSK Modem
CMX469A
Notes
Min.
Typ.
Max.
Units
Carrier Detect
3
Sensitivity
1, 7, 8
-
-
150
mVrms
Probabilty of CD being High after bit 16:
with SNR = 12dB
9
9
0.995
0.05
with 230mVrms Noise and No Signal
Transmitter Output
Tx Output Level
Output Level Variation for 1200/1800Hz
or 1200/2400Hz or 2400/4800Hz
1
-
775
-
-
mVrms
dB
0
+/-1.0
Output Distortion
3rd Harmonic Distortion
10
10
-
-
3.0
2.0
5.0
3.0
%
%
Isochronous Distortion
1200Hz - 1800Hz/1800Hz - 1200Hz
1200Hz - 2400Hz/2400Hz - 1200Hz
2400Hz - 4800Hz/4800Hz - 2400Hz
-
-
-
25.0
20.0
10.0
40.0
30.0
20.0
µs
µs
µs
Logic ‘1’ Carrier Frequency 1200 Baud
6
6
6
6
6
6
-
-
-
-
-
-
1200
1200
2400
1800
2400
4800
-
-
-
-
-
-
Hz
Hz
Hz
Hz
Hz
Hz
2400 Baud
4800 Baud
Logic ‘0’ Carrier Frequency 1200 Baud
2400 Baud
4800 Baud
Notes:
1. Measured at V = 5.0 volts. Signal levels and thresholds are proportional to V
DD
DD.
2. Excludes any current drawn by external components, but includes current drawn by the crystal
components.
3. See Figure 6 (Typical Variation of BER with Input Signal Level).
4. SNR = Signal-to-Noise Ratio in the Bit-Rate Bandwidth.
5. See Figure 7 (Typical Rx BER vs Signal-to-Noise Ratio).
6. Dependent upon Xtal tolerance.
7. With an alternating (1010...) pattern.
8. Measured with a 150mVrms input signal (no noise).
9. A signal level of 230mVrms is used in C.D. probability measurements. Noise bandwidth is 5kHz
(1200/2400 baud operation) or 8kHz (4800 baud operation). See Section 1.4, Note 2 for details
on optimising noise immunity.
10. For an unmodulated carrier.
ã 2001 Consumer Microcircuits Limited
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D/469A/2
1200/2400/4800 Baud FFSK/MSK Modem
CMX469A
Interface Timing Diagrams
tESET
Tx
ENABLE
Tx
SYNC
t DH
tTDR
tTDR
tDSET
DC
DV
=
=
Don't Care
Data Valid
Tx DATA
DC
DC
DC
DC
DV
DV
DV
tTxD
OPEN CIRCUIT
OPEN CIRCUIT
OPEN CIRCUIT
OPEN CIRCUIT
1200 BAUD
Tx OUTPUT
2400 BAUD
Tx OUTPUT
TX DATA must be valid at the time of the rising edge of TX SYNC.
Therefore the optimum time to change TX DATA is on the falling edge of TX SYNC.
Figure 4 Transmitter Timing
Rx
SIGNAL I/P
2400/4800 BAUD
LOGIC '0'
LOGIC '1'
Rx
SIGNAL I/P
1200 BAUD
tID
1
Rx
SYNC O/P
(1200Hz)
0
Undetermined
State
t RDR
1
CLOCKED
DATA O/P
LOGIC '1'
LOGIC '0'
0
The optimum time to sample the CLOCKED DATA O/P is on the falling edge of RX SYNC O/P.
Figure 5 Receiver Timing
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1200/2400/4800 Baud FFSK/MSK Modem
CMX469A
1.7.1 Electrical Performance (continued)
Interface Timings
Notes
Min.
2.0
2.0
2.0
-
Typ.
Max.
Units
tESET
tDSET
tDH
Tx Delay, Signal to Disable Time
Data Set-Up Time
2
1
-
-
800
µs
µs
µs
µs
µs
µs
µs
ms
-
-
Data Hold Time
-
tTXD
tTDR
tRDR
Tx Delay to O/P Time
Tx Data Rate Period
1.2
833
-
-
2
2
-
-
Rx Data Rate Period
Undetermined State (see Figure 5)
Internal Rx Delay
800
-
865
2.0
-
-
tID
-
1.5
Notes:
1. Consider the Xtal/Clock tolerance.
2. 1200 Baud example.
1
1
1
x
x
x
10-1
*
BIT RATE BANDWIDTH
10 -2
10-3
2
0
d
B
S
N
R
1
1
x
x
10-4
10-5
500
150
200
250
300
700
800
100
50
INPUT SIGNAL LEVEL (mVrms)
Figure 6 Typical Variation of Bit Error Rate with Input Level
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1200/2400/4800 Baud FFSK/MSK Modem
CMX469A
Figure 7 Typical Rx Bit Error Rate vs Signal-to-Noise Ratio
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D/469A/2
1200/2400/4800 Baud FFSK/MSK Modem
CMX469A
1.7.2 Packaging
Figure 8 D3 Mechanical Outline: Order as part no. CMX469AD3
Figure 9 E2 Mechanical Outline: Order as part no. CMX469AE2
ã 2001 Consumer Microcircuits Limited
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D/469A/2
1200/2400/4800 Baud FFSK/MSK Modem
CMX469A
Figure 12 P6 Mechanical Outline: Order as part no. CMX469AP6
Handling precautions: This product includes input protection, however, precautions should be taken to prevent device damage from
electro-static discharge. CML does not assume any responsibility for the use of any circuitry described. No IPR or circuit patent
licences are implied. CML reserves the right at any time without notice to change the said circuitry and this product specification.
CML has a policy of testing every product shipped using calibrated test equipment to ensure compliance with this product
specification. Specific testing of all circuit parameters is not necessarily performed.
Oval Park - LANGFORD Telephone: +44 (0)1621 875500
Telefax:
e-mail:
+44 (0)1621 875600
sales@cmlmicro.co.uk
http://www.cmlmicro.co.uk
MALDON - ESSEX
CM9 6WG - ENGLAND
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