High-efficiency switching surge suppressor protects against transients of 200V and higher

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Linear Technology Corporation (Linear Technology Corporation) introduced a high-efficiency switching surge suppressor LTC7860, the device with overvoltage and overcurrent protection for high-availability system. During normal operation, the LTC7860 continuously turns on an external P-channel MOSFET that delivers the input voltage to the output with very low conduction losses. At input overvoltage conditions, the LTC7860 acts as a high efficiency switching DC/DC regulator by controlling the external MOSFET to protect critical downstream components by limiting output voltage and current.

Built on our popular linear surge suppressors (such as the LTC4363), the LTC7860 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 dumping. The power handling capability of a surge suppressor is limited by the power loss in the protection device. In a linear surge suppressor, the power capability is determined by the size of the transmission MOSFET, while in a switching surge suppressor, the power 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 LTC7860 has an input voltage range of 3.5V to 60V and can be extended to 200V and higher with external circuitry. An external fault timer capacitor is responsible for configuring the finite time spent in overvoltage mode and keeping 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), thus reducing system cost and size.

In the MIL-STD-1275 application, the LTC7860 protects devices that rely on a 28V automotive power bus that can operate up to 100V for 500ms. The LTC7860 is ideal for industrial, avionics and automotive power applications including ISO7637 and positive high voltage distributed power hot swap (Hot SwapTM) systems.

The LTC7860 is available in a thermally enhanced 12-lead MSOP package and is priced at $2.95 each in 1,000-piece quantities. The device is available in four temperature grade versions, with extended and industrial temperature grades operating over the –40°C to 125°C temperature range, and high temperature automotive temperature grades operating over the –40°C to 150°C temperature range. The temperature grade version operates over the –55°C to 150°C temperature range. For more information, please visit

Photo description: High efficiency switching surge suppressor

Performance Summary: LTC7860

· SWITCH-ON mode is 100% duty cycle during normal operation

· PROTECTIVE PWM mode for transients and faults

· Wide operating voltage range: 3.5V to 60V

· Input voltage can be extended to over 200V

· Adjustable fault timer

· Adjustable output voltage clamp

· Adjustable output overcurrent protection

· Adjustable soft start for input surge current limit

· Compatible with MIL-STD-1275 and ISO7637

· Optional reverse input voltage protection to -60V

· Extended and industrial temperature grade versions: –40°C to 125°C operating junction temperature range

· Automotive temperature grade version: –40°C to 150°C Operating junction temperature range

· Military temperature grade version: –55°C to 150°C Operating junction temperature range