Provides high efficiency switching protection function
Analog Devices announces the Power by Linear LTC7862, a new switching surge stopper with overvoltage and overcurrent protection for high availability systems. The LTC7862 drives N-channel MOSFETs and, under normal operation, passes the input voltage through to the output with minimal conduction loss. When an input overvoltage condition occurs, the LTC7862 switches as a DC/DC regulator, limiting the output voltage and current to protect critical downstream components.

The LTC7862 builds on the popular linear surge stopper, such as the LTC4363, by providing high efficiency switching protection to extend output current capability and reduce power loss during transients and faults.

When the load current changes abruptly on a long inductive power bus, the supply voltage can rise momentarily. This situation is further aggravated in automotive applications by the energy stored in the alternator inductance, which can cause higher and extended voltage surges during the load dump period. The power handling performance of a surge stopper is limited by the power dissipation in the protection circuit. In a linear surge stopper, the power performance is determined by the size of the pass MOSFET, whereas in a switching surge stopper, the power performance is determined by the conversion efficiency. Because of the lower power dissipation, a switching surge stopper can operate through longer input voltage surges at higher output currents than a linear solution.

The LTC7862 operates over an input voltage range of 4V to 140V (150V abs max). An external fault timer capacitor can be used to set a limited time spent in overvoltage mode, keeping the switching surge stopper below a safe maximum operating temperature range when power loss is at its highest. The fault timer reduces system cost and size by allowing component selection to be optimized for normal operation mode rather than overvoltage transient or fault conditions.

In MIL-STD-1275 applications, the LTC7862 protects devices operating from a 28V automotive power bus, which can reach voltages as high as 100V and last for up to 500ms. The LTC7862 is also suitable for industrial, avionics, and automotive power applications, including ISO 7637.

The LTC7862 is available in 20-lead 4mm x 5mm QFN and TSSOP packages. It is available in three temperature grades, with operation from -40 to 125°C for the extended and industrial grades and a high temp automotive grade of -40 to 150°C.