MT8870DE Very Large Scale Integrated Circuits Ics Complete DTMF Receiver

  Features

   • 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

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 tonepairs 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

• 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

Figure 1 - Functional Block Diagram

Figure 2 - Pin Connections

Functional Description​ 

   The MT8870D/MT8870D-1 monolithic DTMF receiver

offers small size, low power consumption and high

performance. Its architecture consists of a bandsplit

filter section, which separates the high and low group

tones, followed by a digital counting section which

verifies the frequency and duration of the received

tones before passing the corresponding code to the output bus.