Catch the bus

Texas Instruments

has introduced six full-duplex RS-485 transceivers that allow up to 256 devices on a single RS-485 bus.

With electrostatic discharge (ESD) protection in excess of 15 kV (human body model), the products provide an interface for both RS-485 and RS-422 applications such as industrial and building automation, point-of-sale terminals and networks, data terminal equipment/data communications equipment interfaces, and utility meters.

The SN65HVD33/34/35 and SN65HVD53/54/55 are differential line drivers and receivers, with separate input and output pins for full-duplex (4-wire) bus communication designs. The transceivers are designed for interoperation with ANSI TIA/EIA-485A, TIA/EIA-422-B, ITU-T V.11 and ISO 8482:1993 standard-compliant devices.

All the devices sport slew rate-controlled outputs to avoid unwanted reflections, and higher-accuracy data transmission for signalling rates of 1, 5 and 25 Mbps.

Power supply options include 3.3V operation for the HVD3x family and 5V operation for the HVD5x family. When in the low-current standby mode, the HVD3x supply current typically drops to 22 nA, making these devices useful for power-sensitive applications. The HVD5x family provides strong bus drivers with differential output voltages well above the RS-485/RS-422 requirements. This provides signal margin for applications with interconnection losses or noise immunity concerns.

The SN65HVD3x/5x devices are available now from TI and its authorized distributors. The devices are packaged in a 14-pin small-outline integrated circuit (SOIC) package and are priced at $1.85 for the HVD3x devices and $1.75 for the HVD5x devices in 1,000-unit quantities.