Surge stopper protects always-on 4 to 72V electronics

The LTC4380 saves board space and enables continuous operation through transient voltage or current surges.

The surge stopper protects downstream electronics from input overvoltage up to the MOSFET rating, while also protecting the power supply from output overload. Device current consumption is a mere 8µA in normal operation and 6µA in shutdown mode, prolonging battery run and standby time. The low current allows a large filtering resistor to the device supply pin, enabling operation through automotive cold crank and overvoltage transients above 100V.

During an input voltage surge, such as automotive load dump, the LTC4380 drops the excess voltage across the external MOSFET while clamping its gate and therefore the output to a safe voltage. This enables the use of lower voltage rated electronics downstream, saving costs. The clamp voltage is pin-selectable for 12 and 24V systems, or adjustable with an input Zener diode. During an output overload or short-circuit, the LTC4380 regulates the forward path to a current limit set by a sense resistor. For sustained overvoltage or overcurrent conditions, a MOSFET stress-accelerated timeout ensures safe turn-off of the MOSFET. In contrast, traditional protection circuits may blow a fuse or burn out the TVS, requiring repairs.

The LTC4380 withstands a reversed input, such as an incorrectly inserted battery, to -60V. Adjustable input undervoltage lockout threshold blocks start-up for out-of-range voltages, avoiding deeply discharged batteries. The device also controls inrush current during hot plug of a circuit board’s power supply.

The LTC4380 is available in four options: the LTC4380-1 and LTC4380-2 have a pin-selectable clamp voltage; and the LTC4380-3 and LTC4380-4 have a clamp voltage set with an input Zener diode. After a fault, the LTC4380-1 and LTC4380-3 latch the MOSFET off, while the LTC4380-2 and LTC4380-4 automatically turn on with a 0.1% duty cycle. Specified over the 0 to +70°C commercial, -40 to +85°C industrial and -40 to +125°C automotive temperature ranges, the LTC4380 is offered in 10-pin MSOP and 3x3mm DFN packages. Pricing starts at $2.48 each in 1,000 unit quantities.