MAX3250EAI+

Overview

The MAX3250EAI+ is a dual-die, ±50V isolated RS-232 transceiver operating on a single 3.0V to 5.5V logic supply. It provides two drivers and two receivers with a guaranteed data rate of 250kbps. Power transfers across the isolation barrier via external ±100V capacitors (C1, C2). The device features an open-drain FAULT output that triggers when the voltage difference between GND and ISOCOM exceeds 55V. It operates within a temperature range of -40°C to +85°C and is housed in a 28-pin SSOP package.

Feature Summary

• ±50V Isolation Capability: Breaks ground loops caused by high common-mode voltages while maintaining data integrity.
• Integrated Fault Detection: Includes a FAULT pin that signals excessive isolated-side voltage conditions to prevent damage.
• Low-Power Shutdown Mode: Reduces supply current to 20µA and places outputs in a high-impedance state for system power management.
• Inductorless Design: Eliminates transformers or inductors, simplifying EMI compliance and reducing component count.

Applications

• Industrial Control Systems
• Programmable Logic Controllers (PLCs)
• Point-of-Sale Equipment
• PC-to-Router Connections
• Diagnostic Ports

Procurement Notes

Verify the specific suffix 'EAI+' confirms the extended industrial temperature range (-40°C to +85°C) and lead-free/RoHS compliance. Confirm the package type matches the required 28-pin SSOP footprint. Ensure external capacitor ratings meet the specified minimums for proper isolation performance.

Selection Notes

Select this component when high common-mode noise rejection is required without using optocouplers. Verify that the application requires only two drivers and two receivers. Ensure the PCB layout can accommodate the necessary 20mil air gap between logic and isolated sides to maintain the ±50V isolation rating.

Part Context

This part belongs to the MAX3250 family of isolated RS-232 transceivers. The 'E' suffix denotes the extended temperature range variant, while 'AI' specifies the 28-pin SSOP package. The '+' indicates RoHS-compliant manufacturing. It serves as a direct replacement for traditional opto-isolated interfaces in space-constrained designs.

Replacement Considerations

Direct functional replacements include other Maxim Integrated isolated RS-232 transceivers such as the MAX3251 or MAX3252, which offer similar isolation and interface counts but may differ in pinout or specific electrical characteristics.

FAQ

How does the MAX3250 handle power transfer across the isolation barrier?

Power is transferred from the logic side to the isolated side using external ±100V capacitors (C1 and C2). The device drives AC waveforms into these capacitors, which are rectified on the isolated side to generate the internal ISOVCC supply.

What is the function of the SHDN pin?

The SHDN (Shutdown) pin controls the low-power mode. Driving it low enters shutdown, reducing supply current to 20µA and placing receiver/transmitter outputs in a high-impedance state. Driving it high enables normal operation.

What happens if the voltage difference between GND and ISOCOM exceeds 50V?

If the differential voltage exceeds the limit, the FAULT output goes active (low) to signal an overvoltage condition. This allows the processor to monitor the status and prevent potential damage or erroneous operation.