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A new RS-420 driver/receiver from Texas Instruments is well-suited for PCs, laptops and V.34 modems that require much higher data rates and longer cable lengths with increased reliability.
TI's new SN75LBC784 quad driver/receiver complies with the ANSI EIA/TIA-423-B standard.
The V.34 modem specification calls for the use of RS-423 communication devices for external modems in order to achieve the data rates without violating the data communications standards.
Backward compatibility can be maintained with existing RS-232 equipment by adding external resistors to meet the RS-232 input resistance specification of 3K to 7K ohms.
With the slew rate control pin shortened to 5V externally, the driver can support transition times to 1.5us, and typical receiver transition times of 20ns. With RS-423-B, the data rate is increased to 120 kbps and transmission distance to 1.2KM. This is achieved by reducing the maximum output signal swing, increasing the driver output current and reducing the receiver input voltage thresholds.
The SN75LBC784 is available now from Texas Instruments and authorized distributors.
SN75LBC784 28-pin wide body SOIC----$2.64
Suggested resale pricing in U.S. dollars per unit in 1K quantity.
SN75LBC784 Data Sheet (SLLS187)
May, 1995, vol. 12, no.4