POWER AND LINEAR IC SOLUTIONS

New Device Stops High Voltage Surges

Even short duration, high voltage power spikes threaten the electronics in automotive and industrial applications although they may only last from a few µs to hundreds of ms. Critical electronic subsystems must survive these transients, rejecting surges, spikes and transients; in many applications, they must also operate reliably throughout such events.

Linear Technology has developed a new means of blocking surges, spikes and transients commonly found in automotive and industrial systems. The LT4356 eliminates the need for bulky filtering components while isolating low-voltage circuitry from damage. The regulating action eliminates the need for high-voltage rated components downstream of the LT4356, allowing use of inexpensive low-voltage components.

The LT4356 surge stopper implements a series-pass regulator with an external N-channel MOSFET, as can be seen in the diagram of a typical application circuit. Under normal conditions, the LT4356 drives the MOSFET fully on so that input power passes directly through to the load circuitry with little loss. If the input voltage rises beyond a set threshold, the LT4356 begins regulating the output at a safe level.

The oscilloscope trace in the second illustration shows the load dump response. When the input surges to 80V, the output regulates to a safe level. After the surge has dissipated, the LT4356 returns to normal operation or disconnects the output if the fault persists.




In addition to voltage regulation, the LT4356 offers overcurrent and reverse input protection and a ‘micropower' shutdown state that reduces supply current to about 7μA. The LT4356 limits inrush current at turn-on by soft-starting the MOSFET.

The LT4356 tolerates down to -60V on its input and can drive a second reverse-blocking MOSFET to stop the reverse voltage passing through to the load. The LT4356's wide operating voltage range, from 4V minimum to 100V absolute maximum, enables it to operate in systems where the input voltage may sag on the low side as well as surge on the high side of nominal.

The LT4356 surge stopper offers solid front-end protection for electronic control systems. Compared to blocking diodes and filter inductors, it absorbs less board space and reduces heat dissipation and voltage loss. Its higher efficiency and wider usable voltage range allow designers to incorporate more functionality into space-constrained products.

Features

• Front-end protection
• Compact, low heat dissipation
• High efficiency
• Wide operating voltage: 4V to 100V
• Tolerates <-60V reverse input voltage

Applications

• Protection from transients, surges, spikes
• Overcurrent protection, reverse input protection

For further information, including the Linear Technology LT4356 Datasheet and information on how to obtain Demo Board Samples, please click here