The MT8870 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 latch three-state bus interface.
