®
ISO
2
-CMOS
MT8840
Data Over Voice Modem
Features
•
•
•
•
•
•
•
•
•
•
Performs ASK (amplitude shift keyed)
modulation and demodulation
32 kHz carrier frequency
Up to 2 kbit/s full duplex data transfer rate
On-chip oscillator
On-chip tone caller for alerting functions
Adjustable tone caller frequencies
Selectable self-loop test mode
5V/2.5mA power supply
ISO
2
-CMOS and switched capacitor
technologies
18 Pin DIP
MT8840AE
MT8840AS
ISSUE 4
November 1990
Ordering Information
18 Pin Plastic DIP
18 Pin SOIC
0°C to +85°C
Description
The MT8840 is a carrier over voice modem which
allows simultaneous transfer of voice and data over
a single pair of wires. Data is transferred on an
amplitude shift keyed (ASK) 32 kHz carrier. On-chip
filters remove voice frequency signals from the
received composite voice and data signal prior to
demodulation. The modulating signal is a bit stream
with a typical data rate of 2 kbit/s. In addition, the
device contains a two tone warbler which functions
as a telephone ringer. The device is fabricated in
MITEL’s
double-poly
ISO
2
-CMOS
technology
utilizing switched-capacitor techniques.
Applications
•
•
•
Simultaneous data and voice communication in
PABXs
2 kbit/s data modem
"Smart" telephone sets
OSC1
OSC2
CK32
ETC MTC FATC
Timing
and
Control
Tone
Caller
TCO
TxDI
Modulator
TX Bandpass
Filter
TX Post-
Filter
RxDO
Demodulator
AGC
RX Bandpass
Filter
RX Pre-
Filter
R
O
U
T
I
N
G
TxO
RxE
RxI
DET
CRx
V
DD
V
SS
V
Ref
LOOP
Figure 1 - Functional Block Diagram
5-3
MITEL [ MITEL NETWORKS CORPORATION ]
