MAX3085ECSA+T

Overview

The MAX3085ECSA+T is a half-duplex RS-485/RS-422 transceiver manufactured by Analog Devices Inc./Maxim Integrated. It contains one driver and one receiver, operating within a supply voltage range of 4.75V to 5.25V. The device supports data transmission rates up to 500kbps with enhanced slew-rate limiting to minimize EMI. It features ±15kV electrostatic discharge (ESD) protection on all transmitter outputs and receiver inputs using the Human Body Model. The receiver incorporates fail-safe circuitry that guarantees a logic-high output when inputs are open or shorted. Designed for industrial environments, it operates across an extended temperature range from -40°C to +85°C.

Feature Summary

• Enhanced ESD protection rated at ±15kV on I/O pins
• Fail-safe receiver ensures logic-high output during idle bus conditions
• Slew-rate limiting reduces signal reflections and electromagnetic interference
• Supports up to 256 transceivers on a single bus via 1/8-unit-load input impedance

Applications

• RS-422 and RS-485 communication networks
• Industrial control local area networks
• EMI-sensitive applications requiring controlled signal rise times
• Level translation between microprocessors and serial buses

Procurement Notes

Verify the component authenticity through official manufacturer channels or authorized distributors. Confirm the specific suffix 'C' indicates the commercial-to-industrial temperature grade (-40°C to +85°C) and 'SA+' denotes the SOIC-8 surface mount package with lead-free compliance. Ensure the ordering code matches the exact datasheet specifications before finalizing procurement orders.

Selection Notes

Select this model for applications requiring half-duplex communication with data rates up to 500kbps. It is suitable where robust ESD protection and fail-safe operation are critical. Compare against MAX3082E for lower speed requirements or MAX3088E for higher speeds up to 10Mbps. Ensure the system design accommodates the 1/8-unit-load receiver impedance to support multiple nodes on the bus.

Part Context

This component belongs to the MAX3080E–MAX3089E family of high-speed transceivers. The MAX3085E variant specifically targets the 500kbps performance tier, bridging the gap between the 115kbps MAX3082E and the 10Mbps MAX3088E. All devices in this series share common architectural features such as thermal shutdown and low-power standby modes, differing primarily in slew-rate limits and duplex configuration capabilities.

Replacement Considerations

The MAX3085E is pin-compatible with industry-standard parts like the SN75176. Verify that any replacement maintains the same half-duplex functionality and 500kbps slew-rate limitations. Ensure the substitute component also offers ±15kV ESD protection and compatible supply voltage ranges to guarantee direct interchangeability in existing designs.

FAQ

What is the fail-safe behavior of the MAX3085E receiver?

The receiver guarantees a logic-high output if the differential input voltage (A-B) is greater than or equal to -50mV. This occurs when inputs are open, shorted, or connected to a terminated line with all drivers disabled.

How does the MAX3085E handle electromagnetic interference?

It utilizes enhanced slew-rate limiting to reduce the rate of change of the output signals. This minimizes electromagnetic emissions (EMI) and decreases reflections caused by improperly terminated cables.

What is the maximum number of transceivers supported on the bus?

The device features a 1/8-unit-load receiver input impedance, allowing up to 256 transceivers to be connected simultaneously on the same bus.