Diode controller provides negative input protection and low current operation

June 01, 2012 // By Paul Buckley
Linear Technology Corporation has introduced a high voltage ideal diode controller that offers a simple low loss replacement to Schottky diodes, along with key features targeted for automotive, avionics as well as solar applications.

The LTC4359 operates across a wide 4 V to 80 V supply range and withstands input voltages between -40 V to 100 V without damage. Operating current is a low 150 µA, and a shutdown control input enables the LTC4359 to be in a low current shutdown mode, drawing 13 µA. In addition, the LTC4359 is guaranteed for operation across the -40 to 125°C ambient temperature range.

The features enable the LTC4359 to protect loads in harsh automotive environments such as during load dump, cold crank, two-battery jumps, and reverse battery connections. When combined with the LT4363 high voltage Surge Stopper, the LTC4359 provides solid front-end protection from overvoltage, overcurrent and reverse battery. Solar systems also benefit from the low operating current of this device, where the LTC4359 can be used to provide a low loss path that isolates the solar panel from the load.

The LTC4359 controls an external N-channel MOSFET to perform the function of a low forward voltage diode. This provides a lower loss path compared to Schottky diodes and in high power applications provides a more efficient solution and preserves precious board space by reducing the need for heat sinking. In addition, control of back-to-back MOSFETs is available to prevent current flowing from input to output during shutdown. The LTC4359 controls the forward voltage drop across the MOSFET to ensure smooth current delivery without oscillation, even under light loads. If a power source fails or is shorted, a fast <1 µs turn-off minimizes reverse current transients.

The LTC4359 single ideal diode controller can also be used in applications where multiple power supplies are paralleled to provide redundancy. In N+1 redundant systems, an additional supply is added to safeguard the system in the event one of the supplies fail. ORing the supplies together allow disconnection from the power bus for an input failure or hard short. Additionally, the LTC4359 can be used with a reservoir capacitance to