®
ISO
2
-CMOS
MT8870D/MT8870D-1
Integrated DTMF Receiver
Features
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Complete DTMF Receiver
Low power consumption
Internal gain setting amplifier
Adjustable guard time
Central office quality
Power-down mode
Inhibit mode
Backward compatible with
MT8870C/MT8870C-1
ISSUE 3
May1995
Ordering Information
MT8870DE/DE-1 18 Pin Plastic DIP
MT8870DC/DC-1 18 Pin Ceramic DIP
MT8870DS/DS-1 18 Pin SOIC
MT8870DN/DN-1 20 Pin SSOP
MT8870DT/DT-1 20 Pin TSSOP
-40 °C to +85 °C
Description
The MT8870D/MT8870D-1 is a complete DTMF
receiver integrating both the bandsplit filter and
digital decoder functions. The filter section uses
switched capacitor techniques for high and low
group filters; the decoder uses digital counting
techniques to detect and decode all 16 DTMF tone-
pairs into a 4-bit code. External component count is
minimized by on chip provision of a differential input
amplifier, clock oscillator and latched three-state bus
interface.
Applications
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Receiver system for British Telecom (BT) or
CEPT Spec (MT8870D-1)
Paging systems
Repeater systems/mobile radio
Credit card systems
Remote control
Personal computers
Telephone answering machine
VDD
VSS
VRef
INH
PWDN
Bias
Circuit
VRef
Buffer
Q1
Chip Chip
Power Bias
IN +
IN -
GS
Dial
Tone
Filter
High Group
Filter
Zero Crossing
Detectors
Low Group
Filter
Digital
Detection
Algorithm
Code
Converter
and Latch
Q2
Q3
Q4
to all
Chip
Clocks
St
GT
Steering
Logic
OSC1
OSC2
St/GT
ESt
STD
TOE
Figure 1 - Functional Block Diagram
4-11
MITEL [ MITEL NETWORKS CORPORATION ]
