Single–Chip 300–Baud Modem

The MC145442B and MC145443B silicon–gate CMOS single–chip low–speed modems contain a complete frequency shift keying (FSK) modulator, demodulator, and filter. These devices are compatible with CCITT V.21 (MC145442B) and Bell 103 (MC145443B) specifications. Both devices provide full–duplex or half–duplex 300–baud data communication over a pair of telephone lines. They also include a carrier detect circuit for the demodulator section and a duplexer circuit for direct operation on a telephone line through a simple transformer.

• MC145442B Compatible with CCITT V.21

• MC145443B Compatible with Bell 103

• Low–Band and High–Band Band–Pass Filters On–Chip

• Simplex, Half–Duplex, and Full–Duplex Operation

• Originate and Answer Mode

• Analog Loopback Configuration for Self Test

• Hybrid Network Function On–Chip

• Carrier Detect Circuit On–Chip

• Adjustable Transmit Level and CD Delay Timing

• On–Chip Crystal Oscillator (3.579 MHz)

• Single +5 V Power Supply Operation

• Internal Mid–Supply Generator

• Power–Down Mode

• Pin Compatible with MM74HC943

• Capable of Driving –9 dBm into a 600 Ω Load