MT88L70

® ISO2-CMOS MT88L70 3 Volt Integrated DTMF Receiver Features 2.7 - 3.6 volt operation Complete DTMF receiver Low power consumption Internal gain setting amplifier Adjustable guard time Central office quality Power-down mode Inhibit mode ISSUE 2 May 1995 Functionally compatible with Mitel’s MT8870D Applications Paging systems Repeater systems/mobile radio Credit card systems Remote control Personal computers Telephone answering machine PWDN IN + IN GS m o .c U 4 t e e h S a t a .D w w w Description VDD VSS VRef INH Bias Circuit VRef Buffer Chip Chip Power Bias High Group Filter Digital Detection Algorithm Code Converter and Latch Dial Tone Filter Zero Crossing Detectors Low Group Filter to all Chip Clocks St GT Steering Logic OSC1 OSC2 St/GT ESt STD Ordering Information MT88L70AC 18 Pin Ceramic DIP MT88L70AE 18 Pin Plastic DIP MT88L70AS 18 Pin SOIC MT88L70AN 20 Pin SSOP MT88L70AT 20 Pin TSSOP -40 °C to + 85 °C The MT88L70 is a complete 3 Volt, 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. Q1 Figure 1 - Functional Block Diagram m o .c U 4 t e e h S a at .D w...