Fault-Protected, High-Voltage, Signal Line Protector

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The MAX4505 is a single signal-line protector featuring a fault-protected input and rail-to-rail signal handling capability. The input is protected from overvoltage faults up to ±36V with power on or ±40V with power off. During a fault condition, the input terminal becomes an open circuit and only nanoamperes of leakage current flow from the source, while the switch output (AOUT) furnishes typically 19mA from the appropriate polarity supply to the load. This ensures an unambiguous rail-to-rail output when a fault begins and ends.

The MAX4505 protects both unipolar and bipolar analog signals using either unipolar (+9V to +36V) or bipolar (±8V to ±18V) power supplies. The device has no logic control inputs; the protector is always on when the supplies are on. On-resistance is 100Ω max, and on-leakage is less than 0.5nA at TA = +25°C. The MAX4505 is available in 5-pin SOT23 and 8-pin µMAX® packages.
MAX4505: Typical Operating Circuit MAX4505: Typical Operating Circuit Enlarge+

Key Features

  • Overvoltage Protection
    • ±40V with Power Off
    • ±36V with Power On
  • Open Signal Paths with Power Off
  • Output Clamps to Either Rail with an Input Overvoltage
  • 100Ω max On-Resistance
  • 10ns Overvoltage Turn-On Delay
  • No Latchup During Power Sequencing
  • Rail-to-Rail Signal Handling
  • 500Ω Output Clamp Resistance During Overvoltage
  • Tiny 5-Pin SOT23 Package


  • Automated Test Equipment (ATE)
  • Data Acquisition
  • Hot-Insertion Boards/Systems
  • Process Control Systems
  • Redundant/Backup Systems
  • Sensitive Instruments

See parametric specs for Signal-Line Protectors (6)

Part NumberFunctionsSignal Path Leakage
Fault Protect.
(max)(Dual)(max)(See Notes)
MAX4505 1-Line20109.0 to 36.08 to 1810040
$1.59 @1k

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.

Technical Documents

App Note 5299 Selecting the Right CMOS Analog Switch
App Note 745 Fault-Tolerant Analog Switches
Product Reliability Reports: MAX4505.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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