voltage surge suppressor. The device
lead (Fig. 5) and would normally
the plateau (Fig. 6a). Any incoming
voltage surge (Fig. 6b) less than the
load.
?/DIV>
C.
(R
thJA
= 80 K/W for TO-220, and
R
thJA
= 100 K/W for TO-252)
Normal electrostatic handling
precautions for MOS devices
should be adhered to.
Fig. 5. DC surge suppression
Soft Start-Up Circuits
Here the regulator characteristic will
clamp initial current surges which can
occur when power is initially applied
to a load. The device, with its 450 V
capability could, for example, be used
with a DC power supply or with AC
mains to limit the initial high inrush of
current into lamp filaments, thereby
increasing the filament life several
times. It could, therefore, be used
effectively in lighting displays and in
the transportation lighting industries.
Highly Stable Voltage Sources
Another obvious application would be
to use the current regulator as a
Fig. 9.  Normal fusing links in
series with each board
Fig.8. Low cost current regulators
instead of fuses
Fig. 6b. Incoming surge/output surge
across load
Fig. 6a. DC surge suppression
source of a highly stable current to
produce a usable voltage reference
(Fig. 7). This would be effectively
independent of temperature and a low
cost approach. A high voltage
reference is also possible, thanks to
their high breakdown voltages.
Instantaneous "Fuse"
Another application would be
protection against sudden voltage
droops on voltage supply lines to logic
cards in computing systems, resulting
from one component suddenly
shorting to ground. Normal fusing
networks will draw considerable
current during the time it takes for the
fuse to clear. This could cause a
sufficient dip in power rail voltage to
cause malfunctions of the other logic
cards, even with fast-blow fuses (Fig.
8). The current regulator in series with
the logic card restricts the current to
its own operating level (Fig. 9).
Therefore the voltage supply does not
become overloaded and the regulator
remains intact.
The current regulator thus provides an
"instantaneous fusing" function. When
the logic component is replaced, the
regulator   resumes   its   normal
functioning mode.
The obvious advantages to having this
regulator as fuse substitute are:
Prevents a "dip" in the power
supply during a fault condition
Regulator remains intact
Can be easily tied in with logic to
indicate a "down state" board
R = 100 &   V
out
= 3.5 V nominal
R = 50 &
V
out
= 1.75 V nominal
R = 25 &
V
out
= 0.875 V nominal
Fig. 7. Simple voltage source with
high stability
IXC Series
IXYS MOSFETs and IGBTs are covered by 4,835,592    4,931,844
5,049,961
5,237,481
6,162,665
6,404,065 B1    6,683,344
6,727,585
one or moreof the following U.S. patents:    4,850,072    5,017,508
5,063,307
5,381,025
6,259,123 B1
6,534,343
6,710,405B2    6,759,692
4,881,106    5,034,796
5,187,117
5,486,715
6,306,728 B1
6,583,505
6,710,463