M-8880 Datasheet, PDF (1/13 Pages) Clare, Inc. – M-8880 DTMF Transceiver

M-8880 DTMF Transceiver
· Advanced CMOS technology for low power consump-
tion and increased noise immunity
· Complete DTMF transmitter/receiver in a single chip
· Standard 6500/6800 series microprocessor port
· Central office quality and performance
· Adjustable guard time
· Automatic tone burst mode
· Call progress mode
· Single +5 Volt power supply
· 20-pin DIP and SOIC packages
· 2 MHz microprocessor port operation
· Inexpensive 3.58 MHz crystal
· No continuous f2 clock required, only strobe
· Applications include: paging systems, repeater sys-
tems/mobile radio, interconnect dialers, PBX systems,
computer systems, fax machines, pay telephones,
credit card verification
The M-8880 is a complete DTMF Transmitter/Receiver that fea-
tures adjustable guard time, automatic tone burst mode, call
progress mode, and a fully compatible 6500/6800 microproces-
sor interface. The receiver portion is based on the industry stan-
dard M-8870 DTMF Receiver, while the transmitter uses a
switched-capacitor digital-to-analog converter for
low-distortion, highly accurate DTMF signaling. Tone bursts can
be transmitted with precise timing by making use of the auto-
matic tone burst mode. To analyze call progress tones, a call
progress filter can be selected by an external microprocessor.
Figure 1 Pin Diagram
Functional Description
M-8880 functions consist of a high-performance DTMF receiver
with an internal gain setting amplifier and a DTMF generator that
contains a tone burst counter for generating precise tone bursts
and pauses. The call progress mode, when selected, allows the
detection of call progress tones. A standard 6500/6800 series
microprocessor interface allows access to an internal status
register, two control registers, and two data registers.
Input Configuration
The input arrangement consists of a differential input opera-
tional amplifier and bias sources (V_REF) for biasing the amplifier
inputs at V_DD/2. Provisions are made for the connection of a
feedback resistor to the op-amp output (GS) for gain adjust-
40-406-00012, Rev. G
Figure 2 Block Diagram
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