MC33375

http://onsemi.com

9

THERMAL PROTECTION

Internal thermal limiting circuitry is provided to protect

the integrated circuit in the event that the maximum junction

temperature is exceeded. When activated, typically at

150

°C, the output is disabled. There is no hysteresis built

into the thermal protection. As a result the output will appear

to be oscillating during thermal limit. The output will turn

off until the temperature drops below the 150

°C then the

output turns on again. The process will repeat if the junction

increases above the threshold. This will continue until the

existing conditions allow the junction to operate below the

temperature threshold.

Thermal limit is not a substitute for proper

heatsinking.

The internal current limit will typically limit current to

450 mA. If during current limit the junction exceeds 150

°C,

the thermal protection will protect the device also. Current

limit is not a substitute for proper heatsinking.

OUTPUT NOISE

In many applications it is desirable to reduce the noise

present at the output. Reducing the regulator bandwidth by

increasing the size of the output capacitor will reduce the

noise on the MC33375.

ON/OFF PIN

When this pin is pulled low, the MC33375 is off. This pin

should not be left floating. The pin should be pulled high for

the MC33375 to operate.

Figure 24. SOT–223 Thermal Resistance and Maximum

Power Dissipation versus P.C.B. Copper Length

40

80

120

160

200

280

0.35

0.42

0.50

0.63

0.83

2.50

010

20

30

25

15

5.0

L, LENGTH OF COPPER (mm)

Minimum

Size Pad

2.0 oz. Copper

L

L

Free Air

Mounted

Vertically

240

1.25

Figure 25. SOP–8 Thermal Resistance and Maximum

Power Dissipation versus P.C.B. Copper Length

30

50

70

90

110

170

0.4

0.8

1.2

1.6

3.2

020

40

50

30

10

L, LENGTH OF COPPER (mm)

L

L

130

2.0

150

2.4

2.8

Graph Represents Symmetrical Layout

2.0 oz.

Copper

3.0 mm