MC145442B

This device contains circuitry to protect the inputs against damage due to high static voltages or electric fields; however, it is advised that normal precautions be taken to avoid application of any voltage higher than maximum rated voltages to this highimpedance circuit. For proper operation it is recommended that V_in and V_out be constrained to the range VSS (V_in or V_out) V_DD.

Unused inputs must always be tied to an appropriate logic voltage level (e.g., either V_SS or V_DD).

The MC145442B and MC145443B silicongate CMOS singlechip 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 fullduplex or halfduplex 300baud 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
• LowBand and HighBand BandPass Filters OnChip
• Simplex, HalfDuplex, and FullDuplex Operation
• Originate and Answer Mode
• Analog Loopback Configuration for Self Test
• Hybrid Network Function OnChip
• Carrier Detect Circuit OnChip
• Adjustable Transmit Level and CD Delay Timing
• OnChip Crystal Oscillator (3.579 MHz)
• Single +5 V Power Supply Operation
• Internal MidSupply Generator
• PowerDown Mode
• Pin Compatible with MM74HC943
• Capable of Driving 9 dBm into a 600 Load