MLP1N06CL Datasheet, PDF (3/6 Pages) Motorola, Inc – VOLTAGE CLAMPED CURRENT LIMITING MOSFET

THE SMARTDISCRETES CONCEPT
From a standard power MOSFET process, several active
and passive elements can be obtained that provide on–chip
protection to the basic power device. Such elements require
only a small increase in silicon area and/or the addition of one
masking layer to the process. The resulting device exhibits
significant improvements in ruggedness and reliability as well
as system cost reduction. The SMARTDISCRETES device
functions can now provide an economical alternative to smart
power ICs for power applications requiring low on–resistance,
high voltage and high current.
These devices are designed for applications that require a
rugged power switching device with short circuit protection
that can be directly interfaced to a microcontroller unit
(MCU). Ideal applications include automotive fuel injector
driver, incandescent lamp driver or other applications where
a high in–rush current or a shorted load condition could occur.
OPERATION IN THE CURRENT LIMIT MODE
The amount of time that an unprotected device can with-
stand the current stress resulting from a shorted load before
its maximum junction temperature is exceeded is dependent
upon a number of factors that include the amount
of heatsinking that is provided, the size or rating of the de-
vice, its initial junction temperature, and the supply voltage.
Without some form of current limiting, a shorted load can
raise a device’s junction temperature beyond the maximum
rated operating temperature in only a few milliseconds.
Even with no heatsink, the MLP1N06CL can withstand a
shorted load powered by an automotive battery (10 to 14
Volts) for almost a second if its initial operating temperature
is under 100°C. For longer periods of operation in the cur-
rent–limited mode, device heatsinking can extend operation
from several seconds to indefinitely depending on the
amount of heatsinking provided.
SHORT CIRCUIT PROTECTION AND THE EFFECT OF
TEMPERATURE
The on–chip circuitry of the MLP1N06CL offers an inte-
grated means of protecting the MOSFET component from
high in–rush current or a shorted load. As shown in the sche-
matic diagram, the current limiting feature is provided by an
NPN transistor and integral resistors R1 and R2. R2 senses
the current through the MOSFET and forward biases the
NPN transistor’s base as the current increases. As the NPN
turns on, it begins to pull gate drive current through R1, drop-
ping the gate drive voltage across it, and thus lowering the
voltage across the gate–to–source of the power MOSFET
and limiting the current. The current limit is temperature de-
pendent as shown in Figure 3, and decreases from about 2.3
Amps at 25°C to about 1.3 Amps at 150°C.
Since the MLP1N06CL continues to conduct current and
dissipate power during a shorted load condition, it is impor-
tant to provide sufficient heatsinking to limit the device junc-
tion temperature to a maximum of 150°C.
The metal current sense resistor R2 adds about 0.4 ohms
to the power MOSFET’s on–resistance, but the effect of tem-
perature on the combination is less than on a standard
MOSFET due to the lower temperature coefficient of R2. The
on–resistance variation with temperature for gate voltages of
4 and 5 Volts is shown in Figure 5.
Back–to–back polysilicon diodes between gate and source
provide ESD protection to greater than 2 kV, HBM. This on–
chip protection feature eliminates the need for an external
Zener diode for systems with potentially heavy line transients.
Motorola TMOS Power MOSFET Transistor Device Data
MLP1N06CL
4
VGS = 5 V
VDS = 7.5 V
3
2
1
0
–50
0
50
100
150
TJ, JUNCTION TEMPERATURE (°C)
Figure 3. ID(lim) Variation With Temperature
4
ID = 1 A
3
2
25°C
TJ = –50°C ^150°C
1
0
0
2
4
6
8
10
VGS, GATE–TO–SOURCE VOLTAGE (VOLTS)
Figure 4. RDS(on) Variation With
Gate–To–Source Voltage
1.25
ID = 1 A
1
VGS = 4 V
0.75
VGS = 5 V
0.5
0.25
–50
0
50
100
150
TJ, JUNCTION TEMPERATURE (°C)
Figure 5. On–Resistance Variation With
Temperature
3