-48V Hot-Swap Controllers with External RSENSE

Please check latest availability status for a specific part variant.


The MAX5949A/MAX5949B are hot-swap controllers that allow a circuit card to be safely hot plugged into a live backplane. The MAX5949A/MAX5949B operate from -20V to -80V and are well-suited for -48V power systems. These devices are pin and function compatible with the LT4250 and pin compatible with the LT1640.

The MAX5949A/MAX5949B provide a controlled turn-on to circuit cards preventing glitches on the power-supply rail and damage to board connectors and components. The MAX5949A/MAX5949B provide undervoltage, overvoltage, and overcurrent protection. These devices ensure the input voltage is stable and within tolerance before applying power to the load.

Both the MAX5949A and MAX5949B protect a system against overcurrent and short-circuit conditions by turning off the external MOSFET in the event of a fault condition. The MAX5949A/MAX5949B also provide protection against input voltage steps. During an input voltage step, the MAX5949A/MAX5949B limit the current drawn by the load to a safe level without turning off power to the load.

Both devices feature an open-drain power-good status output (PWRGD-bar for the MAX5949A or PWRGD for the MAX5949B) that can be used to enable downstream converters.

The MAX5949A/MAX5949B are available in an 8-pin SO package. Both devices are specified for the extended -40°C to +85°C temperature range.
MAX5949A, MAX5949B: Typical Operating Circuit MAX5949A, MAX5949B: Typical Operating Circuit Enlarge+

Key Features

  • Allow Safe Board Insertion and Removal from a Live -48V Backplane
  • Pin and Function Compatible with LT4250L (MAX5949A)
  • Pin Compatible with LT1640L (MAX5949A)
  • Pin and Function Compatible with LT4250H (MAX5949B)
  • Pin Compatible with LT1640H (MAX5949B)
  • Circuit-Breaker Immunity to Input Voltage Steps and Current Spikes
  • Withstand -100V Input Transients with No External Components
  • Programmable Inrush and Short-Circuit Current Limits
  • Operate from -20V to -80V
  • Programmable Overvoltage Protection
  • Programmable Undervoltage Lockout
  • Power Up into a Shorted Load
  • Power-Good Control Output


  • -48V Distributed Power Systems
  • Base-Station Line Cards
  • Central-Office Line Cards
  • Central-Office Switching
  • Negative Power-Supply Controls
  • 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
MAX5949 -20-80Current Limit50Latched Off1NegativePin-and-Function Compatible with LT4250
SOIC (N)/8
$2.66 @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.

Quality and Environmental Data

Product Reliability Reports: MAX5949A.pdf 
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.

Quality Management System >
Environmental Management System >


Related Resources