The MAX3157 is a high CMRR RS-485/RS-422 data communications interface providing ±50V isolation in a hybrid microcircuit. A single +5V supply on the logic side powers both sides of the interface, with external ±50V capacitors transferring power from the logic side to the isolated side. Each MAX3157 contains one transmitter and one receiver and is guaranteed to operate at data rates up to 250kbps. Drivers are short-circuit current limited and protected against excessive power dissipation by thermal shutdown circuitry that places the driver outputs into a high-impedance state. 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. The MAX3157 typically draws 25mA of supply current when unloaded or when fully loaded with the driver disabled. Supply current drops to 25µA when the device is placed in shutdown mode. The device is pin selectable between half- and full-duplex mode and also features independently programmable receiver and transmitter output phase through separate pins. The MAX3157 is a low-cost replacement for opto-isolated transceivers. For fully isolated RS-485/RS-422 transceivers, refer to the MAX1480 family data sheet.
The MAX3157 provides a high common‑mode rejection ratio RS‑485/RS‑422 interface with ±50 V isolation in a hybrid microcircuit. It operates from a single +5 V supply and includes built‑in short‑circuit current limiting and thermal shutdown protection. The device supports both half‑ and full‑duplex modes and offers programmable phase control to correct twisted‑pair reversal.
Key features include a fail‑safe receiver that guarantees a logic‑high output when inputs are open or shorted, low‑power shutdown mode drawing only 25 µA, and a wide operating temperature range. The datasheet details absolute maximum ratings, electrical characteristics, switching timings, pin functions, and application guidelines.
| Isolation Voltage | ±50 V |
|---|---|
| Supply Voltage | +5 V (single supply) |
| Maximum Data Rate | 250 kbps |
| Supply Current (no load) | 25 mA |
| Shutdown Current | 25 µA |
| Operating Temperature Range (C‑package) | 0 °C to +70 °C |
| Operating Temperature Range (E‑package) | -40 °C to +85 °C |
The MAX3157 can operate at data rates up to 250 kbps.
It provides ±50 V isolation between the logic side and the isolated side.
The device runs from a single +5 V supply.
In shutdown mode the device draws only about 25 µA.