Signal-Line Overvoltage Protector for Low-Voltage Devices

Protects Low-Voltage Devices Using Sensitive Communication Protocols

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The MAX9940 signal-line overvoltage protector for low-voltage digital communication ports provides protection against high-voltage faults and ESD strikes. The MAX9940 is especially useful for sensitive communication protocols such as Maxim 1-Wire® that cannot afford standard means of fault protection, such as large series resistors or large line capacitances.

The MAX9940 operates from a single supply voltage of +2.2V to +5.5V and consumes only 13µA of quiescent supply current. The EXT port is protected up to 28V. The device features a reaction time of 60ns for fast action during fault conditions and operates over the -40°C to +125°C automotive temperature range.
MAX9940: Block Diagram/Typical Application Circuit MAX9940: Block Diagram/Typical Application Circuit Enlarge+

Key Features

  • 28V Protection on EXT
  • Extended ESD Protection
    • ±4kV IEC 61000-4 Contact on EXT
  • +2.2V to +5.5V Supply Voltage Range
  • 13µA Quiescent Supply Current
  • 60ns Fault Reaction Time
  • Small, 5-Pin SC70
  • -40°C to +125°C Temperature Range


  • Industrial Equipment
  • Notebook Computers
  • Portable Devices
Part NumberFunctionsSignal Path Leakage
Analog Signal Range
Fault Protect.
maxDualmaxSee Notes
MAX9940 1-Line50000 to +5.52.2 to 5.51.1 to 2.2577.528
$0.53 @1k
See All Signal-Line Protectors (6)
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.

MAX9940EVKIT: Evaluation Kit for the MAX9940

Technical Documents

App Note 5299 Selecting the Right CMOS Analog Switch
Tutorial 4671 Improve Sensor Performance and SNR in Pulse Oximeter Designs

Quality and Environmental Data

Product Reliability Reports: MAX9940.pdf 
Lead-Free Package Tin (Sn) Whisker Reports

Additional Resources

Circuit Protection You Might Not Have Thought About

Tools & Models

  • MAX9940 PSPICE Macromodel
  • CAD Symbols and Footprints

  • MAX9940AXK+
  • MAX9940AXK+T
  • Device   Fab Process   Technology   Sample size   Rejects   FIT at 25°C   FIT at 55°C  

    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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