52Mbps Precision Delay RS485 Fail-Safe Transceivers

The LTC1686/LTC1687 are high speed, precision delay, full-duplex RS485 transceivers that can operate at data rates as high as 52Mbps. The devices also meet the requirements of RS422.

A unique architecture provides very stable propagation delays and low skew over a wide common mode and ambient temperature range.

The driver and receiver feature three-state outputs, with disabled driver outputs maintaining high impedance over the entire common mode range. A short-circuit feature detects shorted outputs and substantially reduces driver output current. A similar feature also protects the receiver output from short circuits. Thermal shutdown circuitry protects from excessive power dissipation.

The receiver has a fail-safe feature that guarantees a high output state when the inputs are shorted or are left floating. The LTC1686/LTC1687 RS485 transceivers guarantee receiver fail-safe operation over the entire common mode range (–7V to 12V). Receiver input resistance remains ≥22k when the device is unpowered or disabled.

The LTC1686/LTC1687 operate from a single 5V supply and draw only 7mA of supply current.

Applications

* High Speed RS485/RS422 Full Duplex Transceivers

* Level Translator

* Backplane Transceiver

* STS-1/OC-1 Data Transceiver

* Signal Repeaters

* Precision Propagation Delay Over Temperature: Receiver/Driver: 18.5ns ±3.5ns

* High Data Rate: 52Mbps

* Low tPLH/tPHL Skew: Receiver/Driver: 500ps Typ

* –7V to 12V RS485 Input Common Mode Range

* Guaranteed Fail-Safe Operation Over the Entire Common Mode Range

* High Input Resistance: ≥22k, Even When Unpowered

* Short-Circuit Protected

* Thermal Shutdown Protected

* Driver Maintains High Impedance in Three-State or with Power Off

* Single 5V Supply

* Pin Compatible with LTC490/LTC491

* 45dB CMRR at 26MHz