MAX3157CAI-T

Overview

The MAX3157CAI-T is a high CMRR RS-485/RS-422 data-communications interface providing ±50V isolation in a hybrid microcircuit. It contains one transmitter and one receiver, operating at data rates up to 250kbps with a typical supply current of 25mA. The device uses external ±50V capacitors to transfer power from the logic side to the isolated side, powered by a single +5V supply (4.75V to 5.25V). It features thermal shutdown for driver overload protection and independently programmable receiver and transmitter output phase. The CAI suffix indicates an industrial temperature range of 0°C to +70°C, housed in a 28-pin SSOP package.

Feature Summary

• Provides ±50V isolation using a hybrid microcircuit design without requiring separate isolated power supplies.
• Features true fail-safe receiver operation that guarantees a logic-high output when inputs are open or shorted while maintaining EIA/TIA-485 compliance.
• Includes pin-selectable full-duplex and half-duplex modes along with independent phase control pins to correct for twisted-pair reversals.
• Integrates thermal shutdown circuitry and short-circuit current limiting to protect drivers against excessive power dissipation.

Applications

• Industrial Controls
• Level Translators
• Telecommunications
• Local Area Networks

Procurement Notes

Verify the specific ordering suffix 'T' corresponds to tape-and-reel packaging if required by assembly equipment. Confirm the 'CAI' designation matches the necessary 0°C to +70°C industrial temperature range for the target environment. Ensure the component is sourced from authorized distributors to guarantee authenticity and traceability, as this is a legacy Maxim Integrated product now under Analog Devices.

Selection Notes

Select the MAX3157CAI-T when a low-cost replacement for opto-isolated transceivers is needed in systems requiring ±50V isolation. This part is suitable for applications where a single +5V supply must power both sides of the interface via charge-pump capacitors. Consider the 250kbps maximum data rate and the 28-pin SSOP footprint during PCB layout planning.

Part Context

The MAX3157 belongs to the Maxim Integrated family of high CMRR RS-485 transceivers with isolation. The 'C' grade denotes the commercial/industrial temperature variant, while the 'E' grade covers extended temperatures. The 'I' suffix specifies the SSOP package type, distinct from the PDIP option. This component serves as a direct functional alternative to traditional optocoupler-based isolation schemes in RS-485 networks.

Replacement Considerations

Refer to the MAX1480 family data sheet for fully integrated isolated RS-485/RS-422 transceivers that do not require external charge-pump capacitors. Verify compatibility with existing board space and capacitor requirements when substituting other isolated transceiver models.