Bidirectional circuit breaker protects against current and voltage faults

March 03, 2017 // By Nick Flaherty
Linear Technology has launched a circuit protection controller that provides safe voltage and current levels for 2.5V to 60V electronics in battery-powered automotive, industrial and portable systems.

The LTC4368 replaces fuses, transient voltage suppressors and discrete circuitry for shielding electronics from damaging overcurrent and over-, under- and reverse-voltage conditions. It controls back-to-back N-channel MOSFETs to provide a low loss current path during normal operation, turning them off for overcurrent faults in the forward or reverse direction and provides symmetric forward and reverse current thresholds to protect batteries from excessive charge and discharge currents. The LTC4368-2 circuit breaker trips off when reverse current is detected to prevent backfeeding and hold up the output.

The LTC4368 quickly disconnects the load from input voltages exceeding an adjustable and precise overvoltage threshold, and an adjustable undervoltage lockout disables operation for low input voltages, avoiding deeply discharged batteries. Reverse supply protection isolates the load from batteries inserted with incorrect polarity, eliminating a diode in the power path while the 2.5V operation and lack of a diode drop provide sufficient margin for riding through automotive cold crank conditions. Device current consumption is just 80µA in normal operation and 5µA in shutdown mode, prolonging battery run and standby time and it also controls inrush current while hot plugging a circuit board power supply.

The LTC4368 is available in two options: the LTC4368-1 provides a 50mV reverse circuit breaker sense threshold, whereas the LTC4368-2 has a 3mV reverse threshold. After an overcurrent fault, a pin configuration determines if the MOSFETs are latched off or turned on after a delay. Specified over the 0°C to 70°C commercial, −40°C to 85°C industrial, and −40°C to 125°C automotive temperature ranges, the LTC4368 is offered in 10-pin MSOP and 3mm x 3mm DFN packages. 1,000-piece pricing starts at $1.99 each. Device samples and evaluation circuit boards are available online.

For more information, visit  www.linear.com/product/LTC4368.