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Copyright Microsemi Corp.
Rev 0; 8/26/2010 MicroNote is a trademark of Microsemi Corporation
Zeners and Transient Voltage Suppressors
Can Either Device Be Used For The Same Applications?
This MicroNote will review the differences of Zeners and Transient Voltage
Suppressors (TVSs) for a better understanding of each device and if there are any
applications where they can be combined without serious compromise.
Background History
Zener and TVS semiconductor components have been available for many years. Zener
diodes were the first offered for those applications requiring a shunt (parallel) voltage
regulator starting in the early 1960s. The first generation of silicon p-n junction TVS
devices specifically designed for transient voltage protection followed about ten years
later. The TVS devices were also located in front of the load to be protected and
primarily served as a shunt path to ground for high surge currents that were generated
upstream in the circuit by high-voltage transients such as inductive switching, induced
lightning, and electro-static discharge (ESD) events.
Both of these Zener and TVS semiconductor diode product families primarily use the
avalanche breakdown voltage properties of a silicon p-n junction for their important
features. In that respect, the TVS diode is also sometimes called an “ABD” or Avalanche
Breakdown Diode. Originally the term Zener in semiconductor physics applied only to a
lower voltage reverse breakdown mechanism (typically below 5 volts) involving field
emission or tunneling with relatively high dynamic impedance features as further
described herein. This was named after the initial founder Dr. Clarence Zener for the
lower voltage breakdown mechanism in the late 1950s. However the Zener name now
applies to virtually all voltage regulator diodes including those using avalanche
breakdown up to many hundreds of volts that provide much lower dynamic impedance
qualities (lower change in voltage with increasing current).
Design
Zeners and TVSs are similar in silicon p-n junction diode structures. Both are driven
into reverse breakdown for either regulating or clamping voltage features. However there
can still be notable differences in design and how well they perform for each described
application. This may include how their p-n junctions are fabricated to assure uniformity,
what size p-n junction area is provided, how they may be bonded to adjacent packaging
materials for thermal management, and last but not least how they are electrically tested
or screened for these two product applications. Despite those possible differences, the
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by Kent Walters
Microsemi – Scottsdale, AZ
kwalters@microsemi.com
