-48V Hot-Swap Controllers with External RSENSE and High Gate Pulldown Current

Please check latest availability status for a specific part variant.


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.
MAX5921, MAX5939: Typical Operating Circuit MAX5921, MAX5939: Typical Operating Circuit Enlarge+

Key Features

  • 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


  • Base-Station Line Cards
  • Central-Office Line Cards
  • Network Routers and Switches
  • Server Line Cards
  • Telecom Line Cards
Part NumberVIN
Circuit Breaker/ Current LimitCircuit Breaker/Current Limit Threshold
Fault Condition ControlChannelsPositive/Negative RailFeaturesPackage/PinsBudgetary
minmaxSee Notes
MAX5921 -20-80Current Limit50Periodic Retry1NegativeUndervoltage/Overvoltage Protection
SOIC (N)/8
$2.66 @1k
MAX5939 Latched Off-
SOIC (N)/8
$3.08 @1k
See All Hot Swap Controllers (50)
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.

MAX5921AEVKIT: Evaluation Kit for the MAX5920, MAX5921, and MAX5939

Quality and Environmental Data

Request Reliability Report for: MAX5921 
Lead-Free Package Tin (Sn) Whisker Reports
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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