Features and Benefits

  • Allows Safe Board Insertion and Removal from a Live -48V Backplane
  • Pin-Compatible with LT1640 and LT4250
  • Circuit Breaker Immunity to Input Voltage Steps and Current Spikes
  • 450mA GATE Pulldown Current During Short-Circuit Condition
  • Exponential GATE Pulldown Current
  • Withstands -100V Input Transients with No External Components
  • Programmable Inrush and Short-Circuit Current Limits
  • Operates from -20V to -80V
  • Programmable Overvoltage Protection
  • Programmable Undervoltage Lockout with Built-In Glitch Filter
  • Overcurrent Fault Integrator
  • Powers Up into a Shorted Load
  • Power-Good Control Output
  • Thermal Shutdown Protects External MOSFET

Product Details

The MAX5921/MAX5939 hot-swap controllers allow a circuit card to be safely hot plugged into a live backplane. The MAX5921/MAX5939 operate from -20V to -80V and are well suited for -48V power systems. These devices are pin compatible with both the LT1640 and LT4250 and provide improved features over these devices.

The MAX5921/MAX5939 provide a controlled turn-on to circuit cards preventing damage to board connectors, board components, and preventing glitches on the power-supply rail. The MAX5921/MAX5939 provide undervoltage, overvoltage, and overcurrent protection. These devices ensure that the input voltage is stable and within tolerance before applying power to the load.

Both the MAX5921 and MAX5939 protect a system against overcurrent and short-circuit conditions by turning off the external MOSFET in the event of a fault condition. The MAX5921/MAX5939 protect against input voltage steps by limiting the load current to a safe level without turning off power to the load.

The device features an open-drain power-good status output, active-low PWRGD or PWRGD for enabling downstream converters (see Selector Guide). A built-in thermal shutdown feature is also included to protect the external MOSFET in case of overheating. The MAX5939 features a latched fault output. The MAX5921 contains built-in autoretry circuitry after a fault condition.

The MAX5921/MAX5939 are available in an 8-pin SO package and operate in the extended -40°C to +85°C temperature range.


  • Base-Station Line Cards
  • Central-Office Line Cards
  • Network Routers and Switches
  • Server Line Cards
  • Telecom Line Cards

Product Lifecycle icon-recommended Production

At least one model within this product family is in production and available for purchase. The product is appropriate for new designs but newer alternatives may exist.

Design Resources

ADI has always placed the highest emphasis on delivering products that meet the maximum levels of quality and reliability. We achieve this by incorporating quality and reliability checks in every scope of product and process design, and in the manufacturing process as well.  "Zero defects" for shipped products is always our goal.

PCN-PDN Information

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(*)The 1Ku list pricing shown is for BUDGETARY USE ONLY, shown in United States dollars (FOB USA per unit for the stated volume), and is subject to change. International prices may differ due to local duties, taxes, fees and exchange rates. For volume-specific price or delivery quotes, please contact your local Analog Devices, Inc. authorized distributor. Pricing displayed for Evaluation Boards and Kits is based on 1-piece pricing.


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