MX COM Inc MX469D3, MX469DW, MX469P Datasheet

DATA BULLETIN

MX469

1200/2400/4800bps MSK Modem

1998 MX-COM, Inc. www.mxcom.com Tel: [phone] 744 5050 Fax: [phone] Doc. # 20480081.010

4800 Bethania Station Road, Winston-Salem, NC 27105-1201 USA All trademarks and service marks are held by their respective companies.

Features Applications



Selectable Data Rates

1200/2400/4800bps



Full-Duplex MSK



RX and TX Bandpass Filters



Clock Recovery and
Carrier Detect Capabilities



Pin Selected Xtal/Clock Inputs

1.008MHz or 4.032MHz



Radio and General Applications



Data-Over-Radio



PMR/Cellular Signaling



Portable Data Terminals



Personal/Cordless Telephone

CLOCK

OSCILLA TOR

DIVIDER

DAT A

LA TCH

DIGITAL

PLL

RECTIFIER

S/N

COMP ARATOR

NOISE FILTER

RECTIFIER

RX FILTER

RX ENABLE

DAT A

FILTER

DIGITAL

FILTER

LIMITER LIMITER

RETRIGGERABLE

MONOST ABLE

TX GENERATOR

XT AL/CLOCK

CLOCK RATE

TX DATA I/P

RX SIGNAL I/P

TX SIGNAL O/P

UNCLOCKED

DAT A O/P

CLOCKED

DAT A O/P

RX SYNC O/P

BANDP ASS O/P

CARRIER DETECT O/P

CARRIER DETECT TIME CONST ANT

TX SYNC O/P

TX FILTER

XT AL

f

.. n

V

DD

V

SS

V

BIAS

4800 BPS SELECT

TX ENABLE

1200/ BPS SELECT2400

The MX469 is a full-duplex pin-selectable 1200/2400/4800bps Minimum Shift Key (MSK) Modem for FM radio
links. The mark and space frequencies are 1200/1800, 1200/2400, and 2400/4800Hz respectively. Tone
frequencies are phase continuous; transitions occur at the zero crossing point. The use of a common Xtal
oscillator with a choice of two clock frequencies (1.008MHz or 4.032MHz) provides data-rate, transmit
frequencies, and RX/TX synchronization. The transmitter and receiver operate entirely independently
including individual section powersave functions.

The MX469 includes on-chip circuitry for Carrier Detect and RX Clock Recovery, both of which are made
available at output pins. RX, TX, and Carrier Detect circuits contain bandpass filters to provide high quality
signals in their respective paths. 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.

The MX469 demonstrates high sensitivity and good bit-error-rate under adverse signal conditions.
This low-power device requires few external components and is available in the following packages:

24-pin SOIC (MX469DW), 22-pin PDIP (MX469P), and 20-pin SOIC (MX469D3).

1200/2400/4800bps MSK Modem 2 MX469

1998 MX-COM, Inc. www.mxcom.com Tel: [phone] 744 5050 Fax: [phone] Doc. # 20480081.010

4800 Bethania Station Road, Winston-Salem, NC 27105-1201 USA All trademarks and service marks are held by their respective companies.

Contents

Section Page

1. Block Diagram................................................................................................................3

2. Signal List.......................................................................................................................4

3. External Components....................................................................................................6

4. General Description.......................................................................................................7

4.1 Timing.................................................................................................................................. 7

4.1.1 1200bps ..................................................................................................................................7

4.1.2 2400bps ..................................................................................................................................8

4.1.3 4800bps ..................................................................................................................................9

5. Application ...................................................................................................................10

5.1 Synchronous Modem Design Considerations ................................................................... 10

5.2 Bit Error Rate..................................................................................................................... 11

6. Performance Specifications........................................................................................12

6.1 Electrical Specifications..................................................................................................... 12

6.1.1 Absolute Maximum Limits.....................................................................................................12

6.1.2 Operating Limits....................................................................................................................12

6.1.3 Operating Characteristics......................................................................................................13

6.1.4 Packages ..............................................................................................................................15

MXCOM, Inc. reserves the right to change specifications at any time and without notice.

1200/2400/4800bps MSK Modem 3 MX469

1998 MX-COM, Inc. www.mxcom.com Tel: [phone] 744 5050 Fax: [phone] Doc. # 20480081.010

4800 Bethania Station Road, Winston-Salem, NC 27105-1201 USA All trademarks and service marks are held by their respective companies.

1. Block Diagram

CLOCK

OSCILLATOR

DIVIDER

DATA

LATCH

DIGITAL

PLL

RECTIFIER

S/N

COMPARATOR

NOISE FILTER

RECTIFIER

RX FILTER

RX ENABLE

DATA

FILTER

DIGITAL

FILTER

LIMITER LIMITER

RETRIGGERABLE

MONOSTABLE

TX GENERATOR

XTAL/CLOCK

CLOCK RATE

TX DATA I/P

RX SIGNAL I/P

TX SIGNAL O/P

UNCLOCKED

DATA O/P

CLOCKED

DATA O/P

RX SYNC O/P

BANDPASS O/P

CARRIER DETECT O/P

CARRIER DETECT TIME CONSTANT

TX SYNC O/P

TX FILTER

XTAL

f

.. n

V

DD

V

SS

V

BIAS

4800 BPS SELECT

TX ENABLE

1200/ BPS SELECT2400

Figure 1: Block Diagram

1200/2400/4800bps MSK Modem 4 MX469

1998 MX-COM, Inc. www.mxcom.com Tel: [phone] 744 5050 Fax: [phone] Doc. # 20480081.010

4800 Bethania Station Road, Winston-Salem, NC 27105-1201 USA All trademarks and service marks are held by their respective companies.

2. Signal List

Signal Type Description

PDWD3

1 1 1 Xtal/Clock input 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 Table 3. Operation of any
MX•COM IC without a Xtal or clock input may cause
device damage. To minimize damage in the event of a
Xtal/drive failure, it is recommended that a current
limiting device (resistor or fast-reaction fuse) be installed
on the power supply (V

DD

).

22 2

Xtal

output Output of the on-chip inverter.

3 3 3 TX Sync output A squarewave, produced on-chip, to synchronize the

input of logic data and transmission of the MSK signal
(See Figure 3).

5 5 4 TX Signal output When the transmitter is enabled, this pin outputs the

(140-step pseudo sinewave) MSK signal (See Figure 3).
With the transmitter disabled, this output is set to a high-

impedance state.
6 7 5 TX Data input Serial logic data to be transmitted is input to this pin.
78 6

EnableTX

Input A logic ‘0’ will enable the transmitter (See Figure 3). A

logic ‘1’ at this input will put the transmitter into

powersave while forcing “TX Sync Out” to a logic ‘1’ and

“TX Signal Out” to a high-impedance state. This pin is

internally pulled to V

DD

.

8 9 7 Bandpass output The output of the RX Bandpass Filter. This output

impedance is typically 10k and may require buffering

prior to use.
9 10 8 RX Enable Input The control of the RX function. The control of other

outputs is provided in Table 2

10 11 9 V

BIAS

power The output of the on-chip analog bias circuitry. Held

internally at V

DD

/2, this pin should be decoupled to V

SS

by a capacitor (C2). See Figure 2 and RX Enable notes.

This bias voltage is maintained under all powersave

conditions.

11 12 10 V

SS

power Negative supply (GND).

12 13 11 Unclocked Data output The recovered asynchronous serial data output from the

receiver.

13 14 12 Clocked Data output The recovered synchronous serial data output from the

receiver. Data is latched out by the recovered clock,

available at the “RX Sync O/P”. (See Figure 4 and

Figure 6).

14 15 13 Carrier Detect output For 1200 and 2400bps operation only. When an MSK

signal is being received this output is a logic ‘1’. The

Carrier Detect signal should be ignored during 4800bps

operation.

15 16 14 RX Signal input The MSK signal input for the receiver. This input should

be coupled via a capacitor, C3.

1200/2400/4800bps MSK Modem 5 MX469

1998 MX-COM, Inc. www.mxcom.com Tel: [phone] 744 5050 Fax: [phone] Doc. # 20480081.010

4800 Bethania Station Road, Winston-Salem, NC 27105-1201 USA All trademarks and service marks are held by their respective companies.

Signal Type Description

PDWD3

17 18 15 RX Sync output A flywheel squarewave output. This clock will

synchronize to incoming RX MSK data. (See Figure 4

and Figure 6).

16 19 16

1200/

2400BPS

Select

input A logic ‘1’ on this pin selects the 1200bps 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 2400bps option;

tone frequencies are one-half cycle of 1200Hz represents

a logic ‘1’, one cycle of 2400Hz represents a logic ‘0’.

This pin has an internal 1M pull-up resistor.

Operational Data Rate Configurations are illustrated in

Table 3

18 20 17 4800 BPS Select input A logic '1' on this pin combined with a logic '0' on the

1200/2400 BPS Select pin will select the 4800 option

(1M pulldown resistor). Tone frequencies are: one-half

cycle of 2400Hz represents a logic '1', one cycle of

4800Hz represents a logic '0'. This state can only be

achieved using a 4.032MHz Xtal input. Operational Data

Rate Configurations are illustrated in Table 3

19 21 18 Clock Rate input 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).

20 23 19 Carrier Detect

Time Constant

output Part of the carrier detect integration function. The value

of C4 connected to this pin will affect the carrier detect

response time and therefore the noise performance (See

Figure 2, Note 3).

22 24 20 V

DD

power Positive supply. A single 5-volt supply is required.

4,214, 6,

17,

22

N/C No Internal Connection.

Table 1: Signal List

RX Enable = RX Function Clock Data Output Carrier Detect Rx Sync Out

1 = Enabled Enable Enabled Enabled
0 = Powersave 0 0 1 or 0

Table 2: RX Enable Control Functions

XTAL/CLOCK Frequency 1.008MHz 4.032MHz

Clock Rate pin 00111
1200/2400 Select Pin 10100
4800 Select Pin 00001
Data Rate (bps) 1200 2400 1200 2400 4800

Table 3: Operational Data Rate Configuration