MM74HC942

If Military/Aerospace specified devices are required, please contact the National Semiconductor Sales  ffice/Distributors for availability and specifications.

Supply Voltage (V_CC) ..............-0.5 to +7.0V
Supply Voltage (V^_BB) ..............+0.5 to -7.0V
DC Input Voltage (V_IN) VBB.........-1.5 to V_CC+1.5V
DC Output Voltage (V_OUT) V_BB.........-0.5 to V_CC+0.5V
Clamp Diode Current (I_IK, I_OK)............ ±20 mA
DC Output Current, per pin (I_OUT) ...........±5 mA
DC V_CC or GND Current, per pin (I_CC) .........±50 mA
Storage Temperature Range (T_STG) ..- 65 °C to + 150 °C
Power Dissipation (P_D)
(Note 3) ........................600 mW
S.O. Package only ...................500 mW
Lead Temp. (T_L)
(Soldering 10 seconds)................. 260 °C

The MM74HC942 is a full duplex low speed modem. It provides a 300 baud bidirectional serial interface for data communication over telephone lines and other narrow bandwidth channels. It is Bell 103 compatible.

The MM74HC942 utilizes advanced silicon-gate CMOS technology. Switched capacitor techniques are used to perform analog signal processing.

MODULATOR SECTION
The modulator contains a frequency synthesizer and a sine wave synthesizer. MM74HC942 produces a phase coherent frequency shift keyed (FSK) output.

LINE DRIVER AND HYBRID SECTION
The line driver and hybrid MM74HC942 are designed to facilitate connection to a 600X phone line. They can perform two-to-fourwire    conversion and drive the line at a maximum of 0 dBm.

DEMODULATOR SECTION
The demodulator MM74HC942 incorporates anti-aliasing filters, a receive filter, limiter, discriminator, and carrier detect circuit. The nine pole receive filter provides 60 dB of transmitted tone rejection. The discriminator is fully balanced for stable operation.