Linear Technology’s LT4363 is an over-voltage protection controller that provides over-voltage and over-current 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. Instead, the LT4363 creates a robust, adaptable and 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 builds on Linear’s popular first-generation LT4356 device by extending over-voltage protection capabilities beyond 100 V without sacrificing over-current protection. The IC reacts quickly to over-current and short circuit faults at the load, limiting the current to a safe value set by a sense resistor.
Armed with a 100 V maximum rating and operational capability down to 4 V (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 100 V.
It even survives reversed battery connections to -60 V. 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.
Over-voltage and under-voltage comparator inputs ensure that the LT4363 remains off outside a user-defined voltage range. To limit the thermal stress on the power MOSFET, the device 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 7 μA 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 ICs are offered in 12-pin DFN (4 x 3 mm) and MSOP packages, and a 16-pin SO package with enhanced high-voltage pin spacing.
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