MC33375 Datasheet, PDF (9/12 Pages) ON Semiconductor – LOW DROPOUT MICROPOWER VOLTAGE REGULATOR

MC33375
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
280
Free Air
240
Mounted
Vertically
200
Minimum
160
Size Pad
120
2.50
P_D(max) for T_A = 50°C
1.25
2.0 oz. Copper
L
0.83
ÎÎÎÎ _L
0.63
ÎÎÎÎÎÎÎÎ_0.50
80
0.42
R_θJA
40
0.35
0
5.0
10
15
20
25
30
L, LENGTH OF COPPER (mm)
Figure 25. SOP–8 Thermal Resistance and Maximum
Power Dissipation versus P.C.B. Copper Length
170
3.2
150
P_D(max) for T_A = 50°C
2.8
130
2.4
110
90
70
R_θJA
Graph Represents Symmetrical Layout 2.0
ÎÎÎÎÎÎÎ _{2.0 oz.}
L _Copper
ÎÎÎÎÎÎÎÎÎÎÎÎÎÎ _L
1.6
1.2
3.0 mm
50
0.8
30
0.4
0
10
20
30
40
50
L, LENGTH OF COPPER (mm)
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