Hot-selling and scarce CD22859E Monolithic Silicon COS/MOS Dual-Tone Multifrequency Tone Generator DIP spot stock

Product Descriptions

The CD22859 is a CMOS dual-tone multifrequency (DTMF) tone generator for use in dual-tone telephone dialing systems. The device can easily be interfaced to a standard push-button telephone keyboard to provide enabling operation directly with the telephone lines.

The CD22859 generates standard DTMF sinusoidal dialing tones from an on-chip reference crystal oscillator. The reference oscillator uses an inexpensive 3.579545MHz color TV crystal to create highly stable and accurate tones. The sinusoidal tones are digitally synthesized by a stair-step approximation.

One of four low-frequency band row tones and one of four high-frequency band column tones are selected by driving one of the four row inputs and one of the four column inputs low. Simultaneous selection of more than one row input and/or more than one column input will inhibit tone generation, or generate a single-tone sinusoid. These operating modes are described in the functional truth table.

Control logic is included to allow easy interface to standard K500-type telephones. Two CMOS outputs (TX, RX) capable of driving external pnp receiver and transmitter muting transistors are provided. A low input to the CD pin inhibits tone generation, turns off the reference oscillator and causes TX and RX outputs to go to logic ‘0’. During tone generation mode, CD = 1 and TX, RX = logic 1.

The row, column and CD inputs are provided with pull-up resistors to allow the use of SPST switch matrixes.

Product Features

• Mute Drivers On-Chip

• Device Power can Either be Regulated DC or Telephone Loop Current

• Use of an Inexpensive 3.579545MHz TV Crystal Provide High Accuracy and Stability for all Frequencies

Product Applications

• For Use In Dual-tone Telephone Dialing Systems

Product Photos

For more product information, please download the PDF