MAX3158CAI+

Overview

The MAX3158CAI+ is a high CMRR RS-485/RS-422 data-communications interface providing ±60V isolation in a hybrid microcircuit. It operates on a single +5V supply and supports data rates up to 250kbps. The device contains one transmitter and one receiver, with drivers featuring short-circuit current limiting and thermal shutdown protection. Typical supply current is 25mA when unloaded, dropping to 25µA in shutdown mode. It is housed in a 28-pin SSOP package and operates within a temperature range of 0°C to +70°C.

Feature Summary

• Provides ±60V isolation between logic and cable grounds using external capacitors for power transfer.
• Features fail-safe circuitry that guarantees a logic-high receiver output when inputs are open or shorted.
• Includes independently programmable receiver and transmitter output phase pins to correct for twisted-pair reversal.
• Supports pin-selectable half-duplex and full-duplex operation modes.

Applications

• Industrial Controls
• Telecommunications
• Local Area Networks

Procurement Notes

Verify the component matches the specific commercial grade (C) operating range of 0°C to +70°C and the 28-pin SSOP package configuration. Confirm the presence of the '+' suffix indicates lead-free compliance as per standard manufacturer conventions. Ensure the source provides valid traceability documentation for this Analog Devices / Maxim Integrated product.

Selection Notes

Select this component when an isolated RS-485 or RS-422 interface is required with high common-mode rejection capabilities. It serves as a low-cost alternative to opto-isolated transceivers. Consider the 250kbps maximum data rate and the need for external charge-pump capacitors when designing the circuit layout.

Part Context

The MAX3158CAI+ belongs to the MAX3158 family of high CMRR RS-485 transceivers. The 'C' designation specifies the commercial temperature range, while 'AI' denotes the 28-pin SSOP package. This part is designed to replace older opto-isolated solutions in industrial communication networks requiring galvanic isolation.

Replacement Considerations

Refer to the MAX1480 family data sheet for fully isolated RS-485/RS-422 transceiver alternatives. Other variants in the MAX3158 series include the MAX3158EAI+ for extended temperature ranges and the MAX3158CPI+ in a PDIP package.

FAQ

How does the MAX3158 handle driver overload?

Drivers are protected against excessive power dissipation by thermal shutdown circuitry that places the driver outputs into a high-impedance state if the die temperature becomes excessive.

What is the function of the H/F pin?

The H/F pin selects between half- and full-duplex modes. Connecting it to ISOVCC selects half-duplex, while connecting it to ISOCOM selects full-duplex.

How is the fail-safe feature implemented?

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