Linear announces overvoltage protection controller for high-availability electronic systems

by K C Krishnadas, TechOnline India - January 18, 2012

The LT4363 controller builds on Linear’s first-generation LT4356 device by extending overvoltage protection capabilities beyond 100V without sacrificing overcurrent protection.

Linear Technology has introduced the LT4363, an overvoltage protection controller providing overvoltage and overcurrent protection to high-availability electronic systems.

Supply voltages surge whenever currents flowing through long inductive power buses change abruptly. Also, automotive batteries experience a condition known as load-dump, where the voltage can stay elevated for many milliseconds. Traditional protection circuitry relies on bulky inductors, capacitors, fuses, and transient voltage suppressors, while the LT4363 creates an adaptable, space-efficient design with simple control of an N-channel MOSFET. Only the controller and the MOSFET suffer the high voltage surge; downstream components can afford lower voltage ratings, thereby saving costs.

The LT4363 controller builds on Linear’s LT4356 device by extending overvoltage protection capabilities beyond 100V without sacrificing overcurrent protection. The LTC4363 reacts quickly to overcurrent and short-circuit faults at the load, limiting the current to a safe value set by a sense resistor.

Armed with a 100V maximum rating and operational capability down to 4V (cold-crank), the LT4363 makes for an ideal barrier against badly behaving supplies. A simple clamp on the controller supply extends protection beyond the native 100V. It even survives reversed battery connections to -60V.



During voltage surges, the output is regulated to a voltage set by a resistive divider, allowing the load to operate safely and smoothly through transient events. Overvoltage and undervoltage comparator inputs ensure that the LT4363 remains off outside a user-defined voltage range. To limit the thermal stress on the power MOSFET, the LT4363 uses a VDS–accelerated fault timer. If the fault persists, a warning is issued before the MOSFET is shut off. By limiting the MOSFET gate slew-rate with a resistive-capacitive (RC) network, the controller can be adapted for inrush control in Hot Swap™ applications. In the shutdown state the LT4363 sips just 7µA of supply current, preserving battery life. A built-in thermal shutdown occurs around 150°C.

The LT4363 is available in two options: the LT4363-1 latches off after a fault, whereas the LT4363-2 will retry after a long cool-down period. Specified over the full commercial and industrial temperature ranges, the LT4363 is offered in 12-pin DFN (4mm x 3mm) and MSOP packages, and a 16-pin SO package with enhanced high-voltage pin spacing. Pricing begins at $2.48 each for 1,000-piece quantities and the device is now available in production quantities.

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Summary of Features: LT4363

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)
12-Lead MSOP, (4mm x 3mm) DFN &
16-Lead SO Packages

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