MT8870DE1 [Microchip]

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. It features low power consumption, internal gain setting amplifier, adjustable guard time, central office quality, power-down mode, inhibit mode, and is backward compatible with MT8870C/MT8870C-1. The device minimizes external component count by providing a differential input amplifier, clock oscillator, and latched three-state bus interface.