Datasheet CMX469AP6, CMX469AE2, CMX469AD3 Datasheet (Consumer Microcircuits Limited)

CMX469A

1200/2400/4800 Baud

FFSK/MSK Modem

 2001 Consumer Microcircuits Limited

D/469A/2 May 2001 Provisional Issue

Features Applications

•• Full-Duplex FFSK/MSK Modem with

Separate Rx and Tx Enable Functions

•• Data-Over Radio

•• Personal/Cordless Telephone

•• Pin Selectable Data Rates:

1200, 2400 or 4800 Baud

•• Radio and General Applications

•• Narrowband Coax Data Channels

•• Pin Selectable Xtal/Clock Inputs:

1.008MHz or 4.032MHz

•• Two Way Radio (MPT1327) Signalling

•• Portable Data Terminals

•• 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.

1200/2400/4800 Baud FFSK/MSK Modem CMX469A

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CONTENTS

Section

Page

1.0 Features and Applications.......................................................................2

1.1 Brief Description .......................................................................................2

1.2 Block Diagram ...........................................................................................4

1.3 Signal List...................................................................................................5

1.4 External Components...............................................................................7

1.5 General Description..................................................................................8

1.6 Application Notes......................................................................................9

1.7 Performance Specification.....................................................................10

1.7.1 Electrical Performance..............................................................10

1.7.2 Packaging....................................................................................16

1200/2400/4800 Baud FFSK/MSK Modem CMX469A

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1.2 Block Diagram

Figure 1 Block Diagram

1200/2400/4800 Baud FFSK/MSK Modem CMX469A

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1.3 Signal List

CMX469A

D3 E2 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 2 2 XTALN O/P The output of the on-chip inverter.
3 3 3 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 7 6 Tx DATA I/P I/P The serial logic data to be transmitted is input to

this pin.
6 8 7 Tx ENABLEN 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 V

DD

.

7 9 8 BANDPASS

O/P

O/P The output of the Rx Bandpass Filter. This output

impedance is typically 10k

Ω and may require

buffering prior to use.
8 10 9 Rx ENABLE I/P The control of the Rx function
9 11 10 V

BIAS

BI The output of the on-chip analogue bias circuitry.

Held internally at V

DD

/2, this pin should be

decoupled to V

SS

by a capacitor (C2). This bias
voltage is maintained under all powersave
conditions.

10 12 11 V

SS

PWR Negative supply rail (GND).

11 13 12 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.

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CMX469A

D3 E2 P6 Signal Description

Pin
No.

Pin
No.

Pin
No.

Name Type

13 15 14 CARRIER

DETECT O/P

O/P When an FFSK/MSK signal is being received

this output is a logic ‘1’.

14 16 15 Rx SIGNAL I/P I/P The FFSK/MSK signal input for the receiver. This

input should be coupled via a capacitor, C3.

15 18 17 Rx SYNC O/P O/P A flywheel squarewave output. This clock will

synchronize to incoming Rx FFSK/MSK data.

16 19 16 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 1M

Ω 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 (1M

Ω 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 21 19 CLOCK RATE I/P 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).

19 22 20 CARRIER

DETECT TIME

CONSTANT

BI 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.

20 24 22

V

DD

PWR Positive supply rail. A single 2.7 to 5.0 volt

supply is required. This pin should be decoupled
to V

SS

by a capacitor (C5).

4, 6,

17, 23

4, 21

No internal connection, do not use.

Notes: I/P = Input O/P = Output BI = Bidirectional PWR = Power

1200/2400/4800 Baud FFSK/MSK Modem CMX469A

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1.4 External Components

Component Value

R1

1.0MΩ
C1 33.0pF
C2 1.0µF
C3 0.1µF
C4 0.1µF
C5 1.0µF
C6 1.0µF
C7 33.0pF
X1 1.008MHz

or

4.032MHz

Notes:

1. V

BIAS

may be decoupled to VSS and VDD using C2 and C6 when input signals are referenced to the V

BIAS

pin. For input signals referenced to V

SS

, decouple V

BIAS

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

1200/2400/4800 Baud FFSK/MSK Modem CMX469A

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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.

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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 Clock Data O/P Carrier Detect O/P Rx Sync Out

‘1’ Enabled Enabled Enabled Enabled
‘0’ Powersave ‘0’ ‘1’ or ‘0’ ‘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’

‘0’ ‘1’ ‘1’ ‘1’

1200/2400
Select

‘1’

‘0’ ‘1’ ‘0’ ‘0’

4800 Select ‘0’

‘0’ ‘0’ ‘0’ ‘1’

Baud Rate 1200

2400 1200 2400 4800

Test Set Up

Figure 3 Suggested CMX469A Test Set-Up

1200/2400/4800 Baud FFSK/MSK Modem CMX469A

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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 (VDD - VSS) -0.3 7.0 V
Voltage on any pin to V

SS

-0.3 V

DD

+ 0.3 V

Current into or out of VDD and V

SS

pins -30 +30 mA

Current into or out of any other pin -20 +20 mA

D3 Package

Min. Max. Units

Total Allowable Power Dissipation at Tamb = 25°C

800 mW

... Derating

13 mW/°C
Storage Temperature -55 +125 °C
Operating Temperature -40 +85 °C

E2 Package

Min. Max. Units

Total Allowable Power Dissipation at Tamb = 25°C

320 mW
... Derating

5.3 mW/°C
Storage Temperature -55 +125 °C
Operating Temperature -40 +85 °C

P6 Package

Min. Max. Units

Total Allowable Power Dissipation at Tamb = 25°C

800 mW

... Derating

13 mW/°C
Storage Temperature -55 +125 °C
Operating Temperature -40 +85 °C

1200/2400/4800 Baud FFSK/MSK Modem CMX469A

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Operating Limits

Correct operation of the device outside these limits is not implied.

Notes Min. Max. Units

Supply (VDD - VSS)

2.7 5.5 V

Operating Temperature

-40 +85 °C

Xtal Frequency 1 4.028 4.036 MHz
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

DD

= 3.0V to 5.5V at Tamb = −40°C to +85°C,

Xtal/Clock Frequency = 4.032MHz, Bit Rate = 1200 baud, Rx Input Level = 300mVrms.

Notes Min. Typ. Max. Units

Static Values

IDD Rx Enabled, Tx Disabled (VDD = 5.0V) 2 - 3.6 - mA
I

DD

Rx and Tx Enabled (VDD = 5.0V) 2 - 4.5 - mA

I

DD

Rx and Tx Disabled (VDD = 5.0V) 2 - 650 - µA

I

DD

Rx Enabled, Tx Disabled (VDD = 3.0V) 2 - 1.5 - mA

I

DD

Rx and Tx Enabled (VDD = 3.0V) 2 - 2.0 - mA

I

DD

Rx and Tx Disabled (VDD = 3.0V) 2 - 300 - µA

Logic ‘1’ Level

1 70% - - V

DD

Logic ‘0’ Level

1 - - 30% V

DD

Digital Output Impedance

- 4.0 -

kΩ

Analogue and Digital Input Impedance

100 - -

kΩ

Tx Output Impedance (V

DD

= 5.0V)

- 0.6 1.0

kΩ

Dynamic Values
Receiver

Signal Input Dynamic Range SNR = 50dB

3, 4 100 230 1000 mVrms

Bit Error Rate at SNR = 12dB

4, 5

1200 Baud

- 2.5 - 10-4

2400 Baud

- 1.5 - 10

-3

4800 Baud

- 1.5 - 10

-3

Bit Error Rate at SNR = 20dB 4, 5
1200/2400/4800 Baud

- <1.0 - 10

-8

Receiver Synchronization at SNR = 12dB
probability of bit 16 being correct 7 - 0.995 -

1200/2400/4800 Baud FFSK/MSK Modem CMX469A

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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

0.995

with 230mVrms Noise and No Signal 9

0.05

Transmitter Output

Tx Output Level 1 - 775 - mVrms
Output Level Variation for 1200/1800Hz
or 1200/2400Hz or 2400/4800Hz

0

-

+/-1.0

dB

Output Distortion 10 - 3.0 5.0 %
3rd Harmonic Distortion 10 - 2.0 3.0 %
Isochronous Distortion
1200Hz - 1800Hz/1800Hz - 1200Hz

- 25.0 40.0 µs

1200Hz - 2400Hz/2400Hz - 1200Hz

- 20.0 30.0 µs

2400Hz - 4800Hz/4800Hz - 2400Hz

- 10.0 20.0 µs

Logic ‘1’ Carrier Frequency 1200 Baud 6 - 1200 - Hz
2400 Baud 6 - 1200 - Hz
4800 Baud 6 - 2400 - Hz
Logic ‘0’ Carrier Frequency 1200 Baud 6 - 1800 - Hz
2400 Baud 6 - 2400 - Hz
4800 Baud 6 - 4800 - Hz

Notes:

1.

Measured at V

DD

= 5.0 volts. Signal levels and thresholds are proportional to V

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.

1200/2400/4800 Baud FFSK/MSK Modem CMX469A

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Interface Timing Diagrams

Tx

ENABLE

Tx

SYNC

Tx DA TA

2400 BAUD

Tx OUTPUT

1200 BAUD

Tx OUTPUT

OPEN CIRCUIT

OPEN CIRCUIT

OPEN CIRCUIT

OPEN CIRCUIT

DC = Don't Care
DV = Data Valid

DV

DC

DV

DC

DV

DC DC

t

ESET

t

TxD

t

DSETDSET

t

DH

t

TDR

t

TDR

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
1200 BAUD

Rx

SIGNAL I/P

2400/4800 BAUD

Rx

SYNC O/P

(1200Hz)

CLOCKED

DA TA O/P

1

1

0

0

LOGIC '1'

t

ID

t

RDR

Undetermined

State

LOGIC '0'

LOGIC '1' LOGIC '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

1200/2400/4800 Baud FFSK/MSK Modem CMX469A

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1.7.1 Electrical Performance (continued)

Interface Timings Notes Min. Typ. Max. Units

t

ESET

Tx Delay, Signal to Disable Time 2 2.0 - 800 µs

t

DSET

Data Set-Up Time 1 2.0 - - µs

t

DH

Data Hold Time 2.0 - - µs

t

TXD

Tx Delay to O/P Time - 1.2 - µs

t

TDR

Tx Data Rate Period 2 - 833 - µs

t

RDR

Rx Data Rate Period 2 800 - 865 µs

Undetermined State (see Figure 5) - - 2.0 µs

t

ID

Internal Rx Delay - 1.5 - ms

Notes: 1. Consider the Xtal/Clock tolerance.

2. 1200 Baud example.

150 200 300

500

700 80

0

INPUT SIGNAL LEVEL (mVrms)

BITERRORRATE

250

100

50

1 x 10

-5

1 x 10

-4

1 x 10

-3

1 x 10

-2

1 x 10

-1

1

0

d

B

S

N

R

*

1

2

d

B

S

N

R

*

2

0

d

B

S

N

R

*

* BIT RATE BANDWIDTH

Figure 6 Typical Variation of Bit Error Rate with Input Level

1200/2400/4800 Baud FFSK/MSK Modem CMX469A

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Figure 7 Typical Rx Bit Error Rate vs Signal-to-Noise Ratio

1200/2400/4800 Baud FFSK/MSK Modem CMX469A

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1.7.2 Packaging

Figure 8 D3 Mechanical Outline: Order as part no. CMX469AD3

Figure 9 E2 Mechanical Outline: Order as part no. CMX469AE2

1200/2400/4800 Baud FFSK/MSK Modem CMX469A

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
MALDON - ESSEX
CM9 6WG - ENGLAND

Telephone: [phone]
Telefax: [phone]
e-mail: [e-mail]
http://www.cmlmicro.co.uk

Figure 12 P6 Mechanical Outline: Order as part no. CMX469AP6