Overvoltage/overcurrent protection controller

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 can also inadvertently be plugged into a device, potentially causing damage from overvoltage or negative supply voltage. The LTC4361 utilises a 2% accurate 5.8V overvoltage threshold to detect an overvoltage event and responds within 1us (max) to isolate the downstream components from the input. Overvoltage protection of up to 80V can be achieved with this ic/mosfet solution without the need of additional external components such as capacitors or transorbs at the input. In addition, the LTC4361 monitors voltage drop across a current sense resistor at the input of the circuit to protect against overcurrent faults. It is targeted for mobile electronics with multiple power supply options like cell phones, MP3/MP4 players, digital cameras that charge via wall and car battery adapters and USB ports. The device controls a low cost external N-channel mosfet so that under normal operation it provides a low loss path from the input to the load. Inrush current limiting is achieved by controlling the voltage slew rate of the gate. If the voltage at the input exceeds the overvoltage threshold of 5.8V, the GATE is pulled low within 1us to protect the load. While the IC operates from supplies between 2.5 and 5.5V, the input pins can withstand 80V transients or DC overvoltages. The LTC4361 features a soft shutdown controlled by the ON pin and 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. Following an overvoltage condition, it automatically restarts with a start-up delay. It is available in two options; the LTC4361-1 latches off after an overcurrent event, where as the LTC4361-2 performs an auto-retry following a 130ms delay. The new LTC4360 overvoltage protection controller is recommended for applications that do not require overcurrent protection. While offering many of the same features as the LTC4361, the two LTC4360 versions are differentiated by pin functions. The LTC4360-1 features soft shutdown control with low shutdown current of 1.5uA, 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 8-lead (2 x 2mm) DFN and SOT-23 packages, and the LTC4360 is offered in a tiny 8-lead SC70 package. Evaluation boards and samples are available online.