The Linear Technology LTC4361 2.5- to 5.5-V overvoltage and overcurrent protection controller is designed to safeguard low-voltage, portable electronics from damaging input voltage transients and current surges. Overvoltage events can occur due to power adapter failure or faults, or when hot-plugging an ac adapter into the power input of the device. The wrong power adapter also can inadvertently be plugged into a device, potentially causing damage from overvoltage or negative supply voltage.

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The LTC4361 uses a 2% accurate 5.8-V overvoltage threshold to detect an overvoltage event and responds within 1 µs (maximum) to isolate the downstream components from the input. Overvoltage protection of up to 80 V can be achieved with this IC/MOSFET solution without the need for additional external components such as capacitors or transorbs at the input. Also, the LTC4361 monitors voltage drop across a current sense resistor at the input of the circuit to protect against overcurrent faults.

The device targets mobile electronics with multiple power-supply options like cell phones, media players, and digital cameras that charge via wall and car battery adapters and USB ports. It controls a low-cost external N-channel MOSFET so it provides a low loss path from the input to the load under normal operation. Controlling the voltage slew rate of the gate also limits the inrush current. If the voltage at the input exceeds the overvoltage threshold of 5.8 V, the gate is pulled low within 1 µs to protect the load.

While the IC operates from supplies between 2.5 and 5.5 V, the input pins can withstand 80-V transients or dc overvoltages. It features a soft shutdown controlled by the ON pin. Also, it provides a gate drive output for an optional external P-channel MOSFET for reverse voltage protection. A power-good output pin indicates gate turn-on. After an overvoltage condition, the LTC4361 automatically restarts without a startup delay. Available in two options, the LTC4361-1 latches off after an overcurrent event, while the LTC4361-2 performs an auto-retry following a 130-ms delay.

Meanwhile, the LTC4360 overvoltage protection controller targets applications that don’t require overcurrent protection. It offers many of the same features as the LTC4361, yet the two versions of the LTC4360 are differentiated by pin functions. The LTC4360-1 features soft shutdown control with low shutdown current of 1.5 µA, while the LTC4360-2 can drive an optional external P-channel MOSFET for negative voltage protection.

Specified over the full commercial and industrial temperature ranges, the LTC4361 is offered in eight-lead (2 by 2 mm) dual-flat no-lead (DFN) and SOT-23 packages, and the LTC4360 comes in a tiny eight-lead SC70 package. Evaluation boards and samples are available online. The LTC4360 costs $1.15 each and the LTC4361 costs $1.40 each, both in 1000-piece lots. Both are available in production quantities.

Linear Technology Corp.