Dual Tone Multiple Frequency Line Interface

The MC145740 is a silicon gate HCMOS LSI designed for general purpose Dual Tone Multiple Frequency (DTMF) communications, and contains a DTMF signal generator and a receiver for all 16 standard digits.
The generator block has a differential line driver which drives a 600 Ω load with 0 dBm level. The transmit signal level is adjusted in 1 dB steps by the programmable attenuator.
The receiver block has an Auto Gain Control (AGC) amplifier to demodulate 50 dB (typ) dynamic range of DTMF signals to the hexadecimal codes.
The device also includes a serial control interface that permits a CPU to exercise the following built–in features.

• Single Power Supply: 3.6 to 5.5 V
• DTMF Generator and Receiver for All 16 Standard Digits
• 0 dBm Line Driver Into 600 Ω Load
• AGC Amplifier
• Programmable Transmit Attenuator
• Serial Control Interface
• Power Down Mode, Less Than 1 µA