V.21/V.23 Telemeter Modem

The MC145745 is a selectable modem chip compatible with ITU V.21 (300 baud full duplex asynchronous) and V.23 mode 2 (1200 baud half duplex asynchronous). The built–in differential line driver has the capability of driving 0 dBm into a 600 Ω load with a 5 V single power supply. This device also includes a DTMF generator, DTMF receiver, call–progress tone detector, answer tone generator, and a receive timing control circuit.

A low consumption device, the MC145745 integrates various functions in a small package. This modem IC is best suited for telemeter and other applications of this type.

• Conforms to ITU V.21 and V.23 Recommendations

• DTMF Generator and Receiver for all 16 Standard Digits

• Capable of Driving 0 dBm into a 600 Ω Load (VCC = 5 V)

• Automatic Gain Control (AGC) Amplifier for the DTMF Receiver

• Call–Progress Tone Detector

• Four–Wire Serial Data Interface (SCP)

• Programmable Transmission and Carrier Detection Levels

• FSK/DTMF Analog Loopback Self–Test Function

• Crystal Oscillator (3.579545 MHz) and Half Divider Circuit (7.159090 MHz) for External Inputs

• Operates in the Voltage Range of 3.3 – 5.5 V

• Power Down Mode (ICC