MLP1N06CL

3

Motorola TMOS Power MOSFET Transistor Device Data

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

u p o n a n u m b e r o f f a c t o r s t h a t i n c l u d e t h e a m o u n t

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.

Figure 3. ID(lim) Variation With Temperature

–50

0

50

100

150

4

1

0

3

2

TJ, JUNCTION TEMPERATURE (°C)

VGS = 5 V

VDS = 7.5 V

Figure 4. RDS(on) Variation With

Gate–To–Source Voltage

0

2

4

6

8

4

1

0

3

2

VGS, GATE–TO–SOURCE VOLTAGE (VOLTS)

10

25

°C

150

°C

ID = 1 A

TJ = –50°C

Figure 5. On–Resistance Variation With

Temperature

–50

0

50

100

150

1.25

0.5

0.25

1

0.75

TJ, JUNCTION TEMPERATURE (°C)

ID = 1 A

VGS = 4 V

VGS = 5 V