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YA862C06R View Datasheet(PDF) - Unspecified

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YA862C06R Datasheet PDF : 0 Pages
Low I R Schottky Barrier Diode Series
Mitsuhiro Kakefu
Masaki Ichinose
1. Introduction
Representative of the recent trends towards small-
er size and higher functionality of portable devices and
towards higher speed CPUs for computers, electronic
devices are rapidly becoming smaller in size, lighter in
weight and are achieving higher performance, and it is
essential that their circuit boards and switching power
supplies be made to consume less power, are more
efficient, generate less noise and support higher densi-
ty packaging. Moreover, in order to suppress the surge
voltage that is applied across a diode during switching
and the noise generated by a steep dv/dt characteristic,
snubber circuits, beads and the like are used, but as a
result the number of components increases, leading to
greater cost. In order to achieve better portability, AC
adapters for notebook computers are being miniatur-
ized; however, the trend toward higher power con-
sumption results in higher internal temperatures,
increasing the severity of the environment in which
these semiconductor devices are used. Consequently,
semiconductor devices are strongly required to provide
the characteristics of lower loss, improved suppression
of thermal runaway, higher maximum operating tem-
perature and lower noise. In particular, an improve-
ment in the characteristics of the secondary source
output rectifying diode, which accounts for nearly 50 %
of the loss in a switching power supply, is strongly
desired.
2. Overview
Schottky barrier diodes (SBDs) exhibit the proper-
ties of low forward voltage (VF), soft recovery and low
noise, and are widely used in the secondary source
rectifying circuits of switching power supplies. Fuji
Electric has previously developed a product line of
conventional 20 to 100 V SBDs (low VF type) and 120
to 250 V SBDs [low reverse current (IR) type] as a
diode series available in a variety of packages and
supporting various output voltages and current capaci-
ties in order to be applicable to a wide range of power
supply applications. However, when the conventional
low VF type SBD operates at high temperatures, its IR
Low IR Schottky Barrier Diode Series
Fig.1 Cross-sectional structure of SBD chip
Guard ring
Schottky electrode
(barrier metal)
SiO2
Epitaxial layer
Si substrate
becomes large, and as a result reverse loss increases,
efficiency decreases and thermal runaway may occur,
making it difficult to use this low VF SBD in a small
power supply packages such as an AC adapter.
The newly developed low IR-SBD is considered to
be the ideal diode for secondary source rectification in
a switching power supply, and is especially well suited
for rectification in a high temperature environment.
Figure 1 shows the cross-sectional structure of the SBD
chip. The chip design incorporates a guard ring to
prevent premature breakdown, and the doping density,
specific resistance and thickness of the epitaxial layer
(n- layer), diffusion depth, and barrier metal that have
been optimized to develop a low IR-SBD series that
provides not only low IR, but also breakdown voltages
of 40, 60 and 100 V, comparable to the conventional VF.
Compared to a conventional SBD having the same
breakdown voltage, this product achieves an approxi-
mate single-digit decrease in IR, a large decrease in
reverse loss, a higher temperature at which thermal
runaway occurs, and a higher maximum operating
temperature. Moreover, this new series has a high
avalanche breakdown voltage and is expected to be
capable of withstanding the large surge voltage that
occurs when a power supply is turned on. The new
series is also expected to enable the design of switching
power supply circuits that realize increased efficiency,
smaller size and greater flexibility. Table 1 lists the
absolute maximum ratings and electrical characteris-
tics of this low IR-SBD series and Fig. 2 shows external
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