CD22859

Semiconductor T UCT ROD ACEMEN 47 P E 7 T L OLE REP 00-442-7 OBS ENDED 8 M ns 1 .com COM pplicatio @harris E R NOSheet tapp ral A Data February 1999 Cent ail: cen l l a m C e or CD22859 File Number 1257.4 Monolithic Silicon COS/MOS Dual-Tone Multifrequency Tone Generator [ /Title The CD22859 is a CMOS dual-tone multifrequency (DTMF) (CD22 tone generator for use in dual-tone telephone dialing systems. The device can easily be interfaced to a standard 859) push-button telephone keyboard to provide enabling /Suboperation directly with the telephone lines. ject (Monol The CD22859 generates standard DTMF sinusoidal dialing tones from an on-chip reference crystal oscillator. The ithic reference oscillator uses an inexpensive 3.579545MHz color SiliTV crystal to create highly stable and accurate tones. The con sinusoidal tones are digitally synthesized by a stair-step approximation. COS/ MOS One of four low-frequency band row tones and one of four Dual- high-frequency band column tones are selected by driving one of the four row inputs and one of the four column inputs Tone Multi- low. Simultaneous selection of more than one row input and/or more than one column input will inhibit tone fregeneration, or generate a single-tone sinusoid. These quency operating modes are described in the functional truth table. Tone Gener- Control logic is included to allow easy interface to standard K500-type telephones. Two CMOS outputs (TX, RX) capable ator) of driving external pnp receiver and tr...