Over-voltage protection regulator replaces bulky protection circuitry

Milpitas, Calif. — Linear Technology Corp. has introduced an over-voltage protection regulator with over-current protection and inrush current limiting for high-availability systems. The LT4356 targets applications where electronic systems must deal with high-voltage surges of short duration such as load dump in automobiles. Applications include automotive, industrial and avionics as well as positive high-voltage distributed power Hot Swap systems.

The LT4356 device offers a wide input operating range of 4-V to 80-V, which enables continuous operation during cold crank conditions where the battery voltage can be as low as 4 V, said Linear. With its high input voltage rating, the LT4356 can handle transient voltages of 100 V and higher, and provides reverse input protection to -30 V without damage to itself or the load.

The LT4356 replaces bulky protection circuitry with a simple IC and FET solution, said Linear. It provides a well-regulated output during an over-voltage transient, allowing continued operation through the event. Front-end protection permits the use of lower cost DC/DC regulators downstream. During an over-voltage event, the LT4356 regulates the output to a user-defined voltage by controlling the gate of an external N-Channel MOSFET. Inrush current limiting is achieved by controlling the voltage slew rate of the gate.

The LT4356 monitors voltage drop across a current sense resistor at the input of the circuit to protect against over-current faults. For either an over-voltage or over-current fault condition, an integrated fault timer ensures safe shutdown of the MOSFET if the fault persists.

An auxiliary amplifier is provided for additional design flexibility. It may be used as a voltage detection comparator or a low drop out (LDO) linear regulator controller. The LT4356 is available in two options defined by the function of the shutdown pin. For the LT4356-1, shutdown of the IC reduces the quiescent current to 5 uA. For the LT4356-2, the auxiliary amplifier and internal reference remain active to ensure a keep-alive supply voltage for vital functions while the main system is shutdown. Quiescent current is reduced to 50 uA during shutdown.

Specified over the full commercial, industrial and automotive temperature ranges (-40°C to 125°C), the LT4356 is offered in 12-pin DFN (4 x 3 mm) and 10-pin MSOP packages. Evaluation kits are available from the factory.

Pricing: Starts at $1.98 each for 1,000-piece quantities.
Availability: Production quantities are available.
Product information: LT4356

Linear Technology Corp. , 1-408-432-1900,

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