High-efficiency N-Channel Switch Surge Suppressor Protects Against 150V Transients

Analog Devices Inc. (ADI) announces the Power by LinearTM LTC7862, a high efficiency switching surge suppressor with overvoltage and overcurrent protection for high availability systems. The LTC7862 drives an N-channel power MOSFET stage. During normal operation, the LTC7862 delivers input voltage to the output with very low conduction losses. At input overvoltage conditions, the LTC7862 acts as a high efficiency DC/DC regulator startup switch to protect critical downstream components by limiting output voltage and current.

Built on our popular linear surge suppressors (such as the LTC4363), the LTC7862 provides high efficiency switching protection to extend output current capability and reduce power loss during transients and faults. In a long inductive power bus, a supply voltage surge occurs when the load current changes abruptly. In automotive applications, the energy stored in the alternator inductance will further exacerbate this situation and cause higher and longer duration voltage surges during load dumps. The power handling capability of a surge suppressor is limited by the power loss of the protection circuit. In a linear surge suppressor, the power handling capability is determined by the size of the transfer MOSFET, while in a switching surge suppressor the power handling capability is dependent on the conversion efficiency. Compared to linear solutions, switching surge suppressors have lower power losses, so they can operate with longer input voltage surge times and higher output currents.

The LTC7862's input voltage operates from 4V to 140V (absolute maximum 150V). An external fault timer capacitor is responsible for configuring the settling time in overvoltage mode and maintaining the switching surge suppressor below a safe peak operating temperature when the power loss is at its highest level. The fault timer optimizes component selection for normal mode (rather than overvoltage transients and fault conditions), thereby reducing system cost and size.

In the MIL-STD-1275 application, the LTC7862 provides protection for devices that operate on a 28V automotive power bus that can reach voltages up to 100V for 500ms. The LTC7860 is also suitable for industrial, avionics and automotive power applications (including ISO 7637).

Relevant LTC78 series products

Author：Brittany Antonia （The author of article owns the copyright.）