AOT500L
N-Channel Enhancement Mode Field
Effect Transistor
TYPICAL PROTECTION CHARACTERISTICS
2.00
Trench BV
1.50
1.00
0.50
0.00
BVCLAMP
D
+
Vz
-
BVDSS(Z)
R
+
-
30
35
40
45
G
+
V
DS (Volts)
Fig 15: BVCLAMP Characteristic
VPLATEAU
This device uses built-in Gate to Source and Gate to Drain zener
protection. While the Gate-Source zener protects against excessive
VGS conditions, the Gate to Drain protection, clamps the VDS well
below the device breakdown, preventing an avalanche condition
within the MOSFET as a result of voltage over-shoot at the Drain
electrode.
S
-
It is designed to breakdown well before the device breakdown.
During such an event, current flows through the zener clamp, which
is situated internally between the Gate to Drain. This current flows at
BVDSS(Z), building up the VGS internal to the device. When the
current level through the zener reaches approximately 300mA, the
VGS is approximately equal to VGS(PLATEAU), allowing significant
channel conduction and thus clamping the Drain to Source voltage.
The VGS needed to turn the device on is controlled with an internally
lumped gate resistor R approximately equal to 10Ω.
60.00
BVCLAMP25oC
50.00
40.00
30.00
20.00
10.00
0.00
BVCLAMP 100oC
VGS(PLATEAU)= 10Ω x 300mA =3V
It can also be said that the VDS during clamping is equal to:
BVDSS = BVCLAMP + VGS(PLATEAU)
0.00E+00 2.50E-06 5.00E-06 7.50E-06 1.00E-05
Additional power loss associated with the protection circuitry can be
considered negligible when compare to the conduction losses of the
MOSFET itself;
Time in Avalanche (Seconds)
Fig 16: Unclamped Inductive Switching
EX:
PL=30µAmax x 16V=0.48mW (Zener leakage loss)
Fig16: The built-in Gate to Drain clamp prevents the device from
going into Avalanche by setting the clamp voltage well below the
actual breakdown of the device. When the Drain to Gate voltage
approaches the BV clamp, the internal Gate to Source voltage is
charged up and channel conduction occurs, sinking the current
safely through the device. The BVCLAMP is virtually temperature
independent, providing even greater protection during normal
operation.
PL(rds)=102A x 6mΩ=300mW (MOSFET loss)
6/7
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