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73K224BL-IGT

V.22bis/V.22/V.21/Bell 212A/103 Single-Chip Modem w/ Integrated Hybrid

TDK Corporation 

73K224BL

V.22bis/V.22/V.21/Bell 212A/103

Single-Chip Modem w/ Integrated Hybrid

DESCRIPTION (continued)

The 73K224BL is pin and software compatible with

the 73K222BL, allowing system upgrades with a

single component change.

The 73K224BL is designed to be a complete

V.22bis compatible modem on a chip. The

complete modem requires only the addition of the

phone line interface, a control microprocessor, and

RS-232 level converter for a typical system. Many

functions were included to simplify implementation

of typical modem designs. In addition to the basic

2400 bit/s QAM, 600/1200 bit/s DPSK and 300

bit/s FSK modulator/demodulator sections, the

device also includes synch/asynch converters,

scrambler/descrambler, call progress tone detect,

DTMF tone generator capabilities and handshake

pattern detectors. Test features such as analog

loop, digital loop, and remote digital loopback are

supported. Internal pattern generators are also

included for self-testing.

FEATURES (continued)

• Adaptive equalization for optimum perform-

ance over all lines

• Programmable transmit attenuation (16 dB,

1 dB steps), selectable receive boost (+18

dB)

• Call progress, carrier, answer tone,

unscrambled mark, S1, and signal quality

monitors

• DTMF, answer and guard tone generators

• Test modes available: ALB, DL, RDL, mark,

space, alternating bit, S1 pattern generation

and detection

• CMOS technology for low power

consumption (typically 100 mW @ 5 V) with

power-down mode (15 mW @ 5 V)

• TTL and CMOS compatible inputs and

outputs

FUNCTIONAL DESCRIPTION

HYBRID AND RELAY DRIVER

To make designs more cost effective and space

efficient, the 73K224BL includes the 2-wire to 4-

wire hybrid with sufficient drive to interface directly

to the telecom coupling transformers. In addition,

an off hook relay driver with 30mA drive capability

is also included to allow use of commonly

available mechanical telecom relays.

QAM MODULATOR/DEMODULATOR

The 73K224BL encodes incoming data into quad-

bits represented by 16 possible signal points with

specific phase and amplitude levels. The base-

band signal is then filtered to reduce intersymbol

interference on the band limited telephone

network. The modulator transmits this encoded

data using either a 1200 Hz (originate mode) or

2400 Hz (answer mode) carrier. The demodulator,

although more complex, essentially reverses this

procedure while also recovering the data clock

from the incoming signal. Adaptive equalization

corrects for varying line conditions by

automatically changing filter parameters to

compensate for line characteristics.

DPSK MODULATOR/DEMODULATOR

The 73K224BL modulates a serial bit stream into

di-bit pairs that are represented by four possible

phase shifts as prescribed by the Bell 212A/V.22

standards. The base-band signal is then filtered to

reduce intersymbol interference on the bandlimited

2-wire PSTN line. Transmission occurs on either a

1200 Hz (originate mode) or 2400 Hz carrier

(answer mode). Demodulation is the reverse of

the modulation process, with the incoming analog

signal eventually decoded into di-bits and

converted back to a serial bit stream. The

demodulator also recovers the clock which was

encoded into the analog signal during modulation.

Demodulation occurs using either a 1200 Hz

carrier (answer mode or ALB originate mode) or a

2400 Hz carrier (originate mode or ALB answer

mode). Adaptive equalization is also used in

DPSK modes for optimum operation with varying

line conditions.

FSK MODULATOR/DEMODULATOR

The FSK modulator produces a frequency

modulated analog output signal using two discrete

frequencies to represent the binary data. The Bell

103 standard frequencies of 1270 and 1070 Hz

2

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