±50V Isolated, 3.0V to 5.5V, 250kbps, 2 Tx/2 Rx, RS-232 Transceiver

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The MAX3250 is a 3.0V to 5.5V powered, ±50V isolated EIA/TIA-232 and V.28/V.24 communications interface with high data-rate capabilities. The MAX3250 is a dual die part that operates with up to ±50V difference between the RS-232 side and the logic side (ISOCOM to GND). This makes the device ideal for operation in noisy conditions with high common-mode voltages. This feature prevents damage to the device if RS-232 lines are inadvertently short-circuited to a +24V or ±48V power bus.

The MAX3250 is powered by a single 3V to 5.5V supply on the logic side. Power is transferred from the logic side to the isolated side by ±100V external capacitors.

The MAX3250 has two receivers (Rx) and two drivers (Tx) and is guaranteed to run at data rates of 250kbps while maintaining RS-232 output levels. The transceivers have a proprietary low-dropout transmitter output stage, delivering true RS-232 performance from a 3V to 5.5V supply with a dual charge pump. The device features an active-low FAULT open-drain output to signal an excessive isolated-side voltage condition on any of the RS-232 inputs. This output can drive an alarm LED or can be monitored by the processor to prevent operation under these conditions. The receiver outputs are high impedance in shutdown, allowing multiple interfaces (IrDA, RS-232, RS-485) to be connected to the same UART.

The MAX3250 is available in a space-saving 28-pin SSOP package.
MAX3250: Typical Operating Circuit MAX3250: Typical Operating Circuit Enlarge+

Key Features

  • Isolation Breaks Ground Loops Due to High Common-Mode Voltages While Maintaining Data Rate
    • ±50V Isolation
    • 250kbps Guaranteed Data Rate
    • Active-Low FAULT Output Signals Excessive Isolated-Side Voltage
  • Integration of Isolation and RS-232 Saves Space
    • SSOP Package
  • Shutdown Allows Multiple Interfaces (IrDA, RS-232, RS-485) to be Connected to the Same UART
    • High-Impedance Transmitter and Receiver Outputs in Shutdown
    • 20µA Supply Current in Shutdown
  • Inductorless/Transformerless Design Simplifies EMI Compliance
  • Low-Cost Replacement for Opto-Isolated Transceivers
  • Meets EIA/TIA-232 Specifications Down to 3.0V


  • Diagnostic Ports
  • Industrial Control
  • PC-to-Router Connections
  • Point-of-Sale Equipment
  • Programmable Logic Controllers
  • Telecom Equipment

Pricing Notes:
This pricing is BUDGETARY, for comparing similar parts. Prices are in U.S. dollars and subject to change. Quantity pricing may vary substantially and international prices may differ due to local duties, taxes, fees, and exchange rates. For volume-specific and version-specific prices and delivery, please see the price and availability page or contact an authorized distributor.
Product Reliability Reports: MAX3250.pdf 
Device   Fab Process   Technology   Sample size   Rejects   FIT at 25°C   FIT at 55°C   Material Composition  

Note : The failure rates are summarized by technology and mapped to the associated material part numbers. The failure rates are highly dependent on the number of units tested.

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