AN957 Datasheet, PDF (5/13 Pages) List of Unclassifed Manufacturers – Measuring HEXFETCharacteristics

Index
AN-957 (v.Int)
7. R_DS(on)
This is the drain-source resistance at 25°C with V_GS = 10V. Since R_DS(on) is temperature-dependent, it is important to minimize
heating of the junction during the test. A pulse test is therefore used to measure this parameter. The test is set up in the following
manner:
1. Connect the device as follows: gate to “B”, drain to “C”, source to “E”.
2. Set the MAX PEAK VOLTS to 15 V.
3. Set the SERIES RESISTOR to 0.3 Ohms.
4. The POLARITY switch should be set to NPN.
5. The MODE switch should be set to “NORM”.
6. Set the STEP AMPLITUDE to 1V.
7. Set NUMBER OF STEPS to 10.
8. Set OFFSET MULT to 0.
9. The CURRENT LIMIT should be set to 500 mA.
10.The STEP MULTIPLIER button should be OUT—that is, 0.1X not
selected.
11.On the PULSED STEPS selector, the 80 microsec button should be IN
(or the 300 microsec, if the 80 is not available).
12.On the RATE selector, the 0.5X button should be IN.
13.Set VERTICAL CURRENT/DIV at 1 amp/div (IRF630). This scale
should be chosen according to the on-resistance of the device being
tested
14.Set the CONNECTION SELECTOR to the “STEP GEN” position in
the “EMITTER GROUNDED” sector.
15.Connect the device using the LEFT/RIGHT switch and raise the
VARIABLE COLLECTOR SUPPLY voltage until the desired value of
drain current is obtained. R_DS(on) is obtained from the trace by reading
the peak values of current and voltage (see Figures 7and 8).
R_DS(on) = VDS/ID.
Logic level devices would have different settings for 6, 7 and 8 so that the
on-resistance is measured at the specified gate voltage
PER
V
1
E
R
T
A
DIV
500 PER
H
O
R
Z
mV
DIV
Figure 7. Drain-source resistance, pulsed mode
PER
V
1
E
R
T
A
DIV
500 PER
H
O
R
Z
mV
DIV
8. V_SD
Figure 8. Drain-source resistance
This is the source-drain voltage at rated current with VGS = 0. It is the forward voltage drop of the body-drain diode when
carrying rated current. If pulsed mode testing is required, use high current test fixture.
1. Connect the device as follows: gate to “B”, drain to “C”, source to “E”.
2. Set the MAX PEAK VOLTS to 15V.
3. Set the SERIES RESISTOR at 1.4 ohms or a value sufficiently low
that rated current can be obtained.
4. Set POLARITY to PNP.
5. Set MODE to "NORM".
6. The 80 microsec button of the PULSED STEPS selector should be IN
(or the 300 microsec, if the 80 is not available).
7. The CONNECTION SELECTOR should be set to the "SHORT"
position in the “EMITTER GROUNDED” sector.
8. HORIZONTAL VOLTS/DIV should be on 200 mV/div.
9. VERTICAL CURRENT DIV should be on 1 amp/div.
10.The DISPLAY button should be set to invert.
PER
V
1
E
R
T
A
DIV
200 PER
H
O
R
Z
mV
DIV
To Order
Figure 9. Source-drain voltage (diode)