The SC9270C/D 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
and dial-tone rejection. Digital counting techniques are employed in
the decoder 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 latched 3-state bus
interface.