MAX3157EAI+

Overview

The MAX3157EAI+ is a high CMRR RS-485/RS-422 data-communications interface providing ±50V isolation in a hybrid microcircuit. It operates on a single +5V supply, typically drawing 25mA when active and dropping to 25µA in shutdown mode. The device supports data rates up to 250kbps and features pin-selectable half- or full-duplex operation. It includes fail-safe receiver circuitry, thermal shutdown protection, and independently programmable output phases. Operating temperature range is -40°C to +85°C, housed in a 28-pin SSOP package.

Feature Summary

• Provides ±50V isolation using external capacitors for power transfer from the logic side.
• Features true fail-safe receiver that guarantees a logic-high output when inputs are open or shorted.
• Includes thermal shutdown circuitry to protect drivers against excessive power dissipation.
• Supports independent phase control for both transmitter and receiver outputs.

Applications

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

Procurement Notes

Verify the specific suffix 'EAI+' corresponds to the extended temperature range (-40°C to +85°C) and SSOP package configuration. Confirm RoHS compliance status through official manufacturer documentation prior to integration. Ensure ordering details match the exact part number to avoid functional discrepancies related to packaging or environmental ratings.

Selection Notes

Select this component for applications requiring galvanic isolation between logic and communication lines without optical components. Consider the 250kbps maximum data rate and ±50V isolation limits. Evaluate the need for half- versus full-duplex modes based on system architecture. Verify that the external capacitor requirements for the charge pump fit within the design constraints.

Part Context

The MAX3157 series serves as a low-cost replacement for opto-isolated transceivers in RS-485 and RS-422 networks. The 'E' designation indicates an industrial temperature range, while 'AI' specifies the 28-pin SSOP surface-mount package. This variant integrates driver and receiver functions into a single hybrid microcircuit for simplified board layout.

Replacement Considerations

Public confirmed substitute part numbers: MAX3157CAI+, MAX3157CPI+, MAX3157EPI+. These variants share identical electrical specifications but differ in operating temperature ranges and physical package types (PDIP vs. SSOP).

FAQ

How is the half/full-duplex mode selected?

The H/F pin selects the mode. Connecting it to ISOCOM enables full-duplex operation, while connecting it to ISOVCC selects half-duplex mode.

What happens if the receiver inputs are left open?

The fail-safe feature guarantees a logic-high receiver output if the inputs are open, shorted, or connected to a terminated line with all drivers disabled.

How does the device handle driver overload?

Thermal shutdown circuitry protects the drivers by placing them into a high-impedance state if the die temperature becomes excessive, typically around +150°C.