Datasheet

MUR480E, MUR4100E
http://onsemi.com
4
t
0
t
1
t
2
t
V
DD
I
D
I
L
BV
DUT
MERCURY
SWITCH
Figure 6. Test Circuit Figure 7. Current−Voltage Waveforms
+V
DD
DUT
40 mH COIL
V
D
I
L
S
1
I
D
The unclamped inductive switching circuit shown in
Figure 6 was used to demonstrate the controlled avalanche
capability of the new “E’’ series Ultrafast rectifiers. A
mercury switch was used instead of an electronic switch to
simulate a noisy environment when the switch was being
opened.
When S
1
is closed at t
0
the current in the inductor I
L
ramps
up linearly; and energy is stored in the coil. At t
1
the switch
is opened and the voltage across the diode under test begins
to rise rapidly, due to di/dt effects, when this induced voltage
reaches the breakdown voltage of the diode, it is clamped at
BV
DUT
and the diode begins to conduct the full load current
which now starts to decay linearly through the diode, and
goes to zero at t
2
.
By solving the loop equation at the point in time when S
1
is opened; and calculating the energy that is transferred to
the diode it can be shown that the total energy transferred is
equal to the energy stored in the inductor plus a finite amount
of energy from the V
DD
power supply while the diode is in
breakdown (from t
1
to t
2
) minus any losses due to finite
component resistances. Assuming the component resistive
elements are small Equation (1) approximates the total
energy transferred to the diode. It can be seen from this
equation that if the V
DD
voltage is low compared to the
breakdown voltage of the device, the amount of energy
contributed by the supply during breakdown is small and the
total energy can be assumed to be nearly equal to the energy
stored in the coil during the time when S
1
was closed,
Equation (2).
The oscilloscope picture in Figure 8, shows the
information obtained for the MUR8100E (similar die
construction as the MUR4100E Series) in this test circuit
conducting a peak current of one ampere at a breakdown
voltage of 1300 V, and using Equation (2) the energy
absorbed by the MUR8100E is approximately 20 mjoules.
Although it is not recommended to design for this
condition, the new “E’’ series provides added protection
against those unforeseen transient viruses that can produce
unexplained random failures in unfriendly environments.
W
AVAL
[
1
2
LI
2
LPK
ǒ
BV
DUT
BV
DUT
–V
DD
Ǔ
W
AVAL
[
1
2
LI
2
LPK
Figure 8. Current−Voltage Waveforms
CHANNEL 2:
I
L
0.5 AMPS/DIV.
CHANNEL 1:
V
DUT
500 VOLTS/DIV.
TIME BASE:
20 ms/DIV.
EQUATION (1):
EQUATION (2):
CH1 CH2 REF REF
CH1
CH2
ACQUISITIONS
SAVEREF SOURCE
1 217:33 HRS
STACK
A
20ms
953 V VERT500V
50mV