MAX5921, MAX5939 -48V Hot-Swap Controllers with External RSENSE and High Gate Pulldown Current

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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.

Key Features

Applications/Uses

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

Key Specifications: Hot Swap Controllers

Part Number

Min. V_IN (V)

Max. V_IN (V)

Low Voltage

High Voltage

Voltage Polarity

Type

Fault Condition Control

Number of Channels

Features

RoHS Available

Package

Smallest Available Package (max w/pins) (mm²)

Operating Temp. Range (°C)

Price^**

MAX5921

-20

-80

Yes

Negative

Negative, High-Voltage

Periodic retry

•	500mA gate-pulldown current during short-circuit protection

•	Immune to Input-Voltage Steps and Current Spikes

•	In-Rush Current and Short Circuit Protection

•	Power-Good output (active-high)

•	Power-Good output (active-low)

•	Programmable OV protection

•	Thermal Shutdown

•	UVLO glitch filter

•	Withstands -100V input transients

Yes

SOIC/8

-40 to +85

$1.90 @ 1k

MAX5939

Latched Off

•	500mA gate-pulldown current during short-circuit protection

•	Immune to Input-Voltage Steps and Current Spikes

•	Improved Replacement for LT1640L & LT4250L

•	In-Rush Current and Short Circuit Protection

•	On/Off Control

•	Power-Good output (active-high)

•	Power-Good output (active-low)

$1.90 @ 1k

See All Hot Swap Controllers (44)

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 prices and delivery, please see the price and availability page or contact an authorized distributor.