ОПИСАНИЕ

The LT4363 surge stopper protects loads from high voltage transients. It regulates the output during an overvoltage event, by controlling the gate of an external N-channel MOSFET. The output is limited to a safe value allowing the loads to continue functioning. The LT4363 also monitors the voltage drop between the SNS and OUT pins to protect against overcurrent faults. An internal amplifier limits the voltage across the current sense resistor to 50mV. In either fault condition, a timer is started inversely proportional to MOSFET stress. Before the timer expires, the FLT pin pulls low to warn of an impending power down. If the condition persists, the MOSFET is turned off. The LT4363-1 remains off until reset whereas the LT4363-2 restarts after a cool down period.

Two precision comparators can monitor the input supply for overvoltage (OV) and undervoltage (UV) conditions. When the potential is below the UV threshold, the external MOSFET is kept off. If the input supply voltage is above the OV threshold, the MOSFET is not allowed to turn back on. Back-to-back MOSFETs can be used in lieu of a Schottky diode for reverse input protection, reducing voltage drop and power loss. A shutdown pin reduces the quiescent current to less than 7µA during shutdown.

 

ОСОБЕННОСТИ

Withstands Surges Over 100V with VCC Clamp

Wide Operating Voltage Range: 4V to 80V

Adjustable Output Clamp Voltage

Fast Overcurrent Limit: Less Than 5µs

Reverse Input Protection to –60V

Adjustable UV/OV Comparator Thresholds

Low 7µA Shutdown Current

Shutdown Pin Withstands –60V to 100V

Adjustable Fault Timer

Controls N-Channel MOSFET

Less Than 1% Retry Duty Cycle During Faults, LT4363-2

Available in 12-Pin (4mm × 3mm) DFN, 12-Pin

MSOP and 16-Pin SO Packages

 

ПРИЛОЖЕНИЯ

Avionic/Industrial Surge Protection

Hot Swap™/Live Insertion

High Side Switch for Battery Powered Systems

Intrinsic Safety Applications

 

ОПЕРАЦИЯ

The LT4363 is an overvoltage protection regulator that drives an external N-channel MOSFET as the pass transistor. It operates from a wide supply voltage range of 4V to 80V. It can also be pulled below ground potential by up to 60V without damage. The internal charge pump turns on the N-channel MOSFET to supply current to the loads with very little power loss. Two MOSFETs can be connected back to back to replace an inline Schottky diode for reverse input protection.This improves the efficiency and increases the available supply voltage level to the load circuitry.

The LT4363 senses an overcurrent condition by monitoring the voltage across an optional sense resistor placed between the SNS and OUT pins. An active current limit circuit (IA) controls the GATE pin to limit the sense voltage to 50mV, if the OUT pin potential is above 2V. In the case of a severe output short that brings OUT below 2V, the servo sense voltage is reduced to 25mV to reduce the stress on the pass transistor. During current limit, the current charging the TMR capacitor is about 5 times the current during an overvoltage event. The FLT pin pulls low when the TMR voltage reaches 1.275V and the MOSFET is turned off when it reaches 1.375V. The MOSFET turns back on and the FLT pin returns to a high impedance state after TMR has reached the 0.5V threshold for the LT4363-2 version. For the latch-off version, LT4363-1, both the GATE and FLT pins remain low even after TMR has reached the 0.5V threshold. Reset the part in the same way as in overvoltage time-out case.

 

ИНФОРМАЦИЯ О ПРИЛОЖЕНИЯХ

The LT4363 limits the voltage and current delivered to the load during supply transient or output overload events. The total fault timer period is set to ride through short-duration faults, while longer events cause the output to shut off and protect the MOSFET pass device from damage. The MOSFET provides a low resistance path from the input to the load during normal operation, while in fault conditions it operates as a series regulator.