Active solid-state devices (e.g. – transistors – solid-state diode – Field effect device – Having insulated electrode
Reexamination Certificate
2002-01-02
2003-02-04
Chaudhuri, Olik (Department: 2813)
Active solid-state devices (e.g., transistors, solid-state diode
Field effect device
Having insulated electrode
C257S341000
Reexamination Certificate
active
06515330
ABSTRACT:
CROSS-REFERENCES TO RELATED APPLICATIONS
NOT APPLICABLE
BACKGROUND OF THE INVENTION
This invention relates generally to power semiconductor devices, and more particularly the invention relates to a power semiconductor current limiting device and a method of making same.
It is known to protect electrical circuits against high input currents by means of a current limiter. A current limiting device works in series with an electrical circuit, contributing a low serial resistance, R
on
, below a given specification. When the circuit is overloaded or malfunctioning, such as output short circuit, resulting in a high current mode outside of normal operation, the current limiting device serves to clamp the current flowing through the circuit, I
lim
, within a given allowance, &Dgr;I
lim
, until the voltage across the current limiting device exceeds its specified operating limit, V
br
. When made by the method taught in the present application, the device provides low R
on
, high I
lim
, low &Dgr;I
lim
, and high V
br
with a wide range of desired I
lim
that is easy to adjust by controlling certain implant energy or dose.
FIG. 1
shows these critical parameters in graphical form.
The present invention is directed to a current limiting device having improved current-voltage characteristics including a lower R
on
, higher I
lim
, lower±&Dgr;I
lim
, and higher V
br
.
BRIEF SUMMARY OF THE INVENTION
In accordance with the invention, a vertical MOS current limiting device has a modified dopant implant. More particularly, in one embodiment serial resistance, R
on
, can be controlled by a shallow P dopant implant and the current limit, I
lim
, can be controlled by a deeper P-dopant implant. The current limiting function is achieved by the overlap of depletion regions by biasing the P-dopant implanted regions.
The invention and objects and features thereof will be more readily apparent from the following detailed description and appended claims when taken with the drawings.
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Christiansen, Bob, “Synchronous Rectification Improves with Age,” PCIM, Aug., 1998, 6 pp.
Chang Paul
Chern Geeng-Chuan
Chiang Ching-Lang
Hurtz Gary M.
Rodov Vladimir
APD Semiconductor, Inc.
Chaudhuri Olik
Townsend and Townsend / and Crew LLP
Vesperman William C.
Woodward Henry K.
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