Littelfuse unveil ultra-low capacitance protection thyristor

3rd September 2013
Nat Bowers

Littelfuse has introduced an ultra-low capacitance protection thyristor, the SDP Series SIDACtor Protection Thyristor in the SOT23-6 package, providing robust overvoltage protection for broadband/xDSL telecommunications equipment with minimal effects on connection speed and reach. Patent-pending silicon crowbar technology allows for 45 percent lower capacitance than clamping devices like transient voltage suppressor diodes.

The SDP Series SIDACtor Protection Thyristor also provides faster response to surges, ensuring lower overshoot voltages and improved electrostatic discharge, lightning and power fault protection. It is designed for the tertiary or line driver side protection position in VDSL2, ADSL2, ADSL2+ telecommunications applications and general I/O protection functions. Its small-footprint package is well-suited for high density card designs.

Crowbar devices operate as shunt devices in response to a surge that exceeds the breakover voltage. After switching on, they offer a very low impedance path that diverts transient energy away from the load. In contrast, clamping devices limit the transient voltage to a set value. When the applied voltage reaches the device’s breakdown value, it switches to a much lower resistance value to minimize the transient energy the circuit will experience.

Betty Li, Global Product Manager for the SIDACtor Protection Thyristor product line, comments: “The SDP Series SOT23-6 is the lowest off-state capacitance crowbarring component on the market and provides the industry’s quickest surge suppression response. It allows circuit designers to provide much faster suppression response to surges than clamping devices while maintaining signal integrity.”


• Helps prevent xDSL driver chip failures by providing a crowbar response to surge events with a maximum threshold of 29V at 250V/µs,
• Provides robust surge protection performance up to 30A while maintaining low off-state capacitance for better AC protection,
• Responds quickly to surges, preventing damage caused by the coupling of transient events across the small signal transformer.


SDP SOT23-6 SIDACtor Protection Thyristors are available on reels in quantities of 3,000. Samples are available now for bulk orders; sample requests can be placed through authorized Littelfuse distributors worldwide.

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