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KA278R12
Low Dropout Voltage Regulator
Features
•
•
•
•
•
2A / 12V Output low dropout voltage regulator
TO220 Full-Mold package (4PIN)
Overcurrent protection, Thermal shutdown
Overvoltage protection, Short-Circuit protection
With output disable function
Description
The KA278R12 is a low-dropout voltage regulator suitable
for various electronic equipments. It provide constant
voltage power source with TO-220F-4 lead full mold
package. Dropout voltage of KA278R12 is below 0.5V in
full rated current(2A). This regulator has various function
such as peak current protection, thermal shut down,
overvoltage protection and output disable function.
TO-220F-4L
1
1. Vin 2. Vo 3. GND 4. Vdis
Internal Block Diagram
Vin
1
Q1
2
Vo
THERMAL SHUTDOWN
OVERVOLTAGE
PROTECTION
BANDGAP REFERENCE
-
+
R1
SOA PROTECTION
HIGH / LOW
Vdis
4
-
+
OUTPUT
ON / OFF
1.4V
SHORT-CIRCUIT
SHORTCIRCUIT
PROTECTION
R2
3
GND
Rev. 1.0.2
©2001 Fairchild Semiconductor Corporation
KA278R12
Absolute Maximum Ratings
Parameter
Input Voltage
Disable Voltage
Output Current
Power Dissipation 1
Power Dissipation 2
Junction Temperature
Operating Temperature
Thermal Resistance, Junction-to Case (Note2)
Thermal Resistance, Junction-to-Air (Note2)
Thermal Shutdown Temperature
Symbol
Vin
Vdis
Io
Pd1
Pd2
Tj
Topr
Rθjc
Rθja
Ttsd
Value
35
35
2.0
1.5
15
150
-20~80
2.9
48.51
150
Unit
V
V
A
W
W
°C
°C
°C/W
°C/W
°C
Remark
-
-
-
No Heatsink
With Heatsink
-
-
-
-
-
Electrical Characteristics
(Vin=15V, Io=1.0A, Ta=25°C , unless otherwise specified)
Parameter
Output Voltage
Load Regulation
Line Regulation
Ripple Rejection Ratio
Dropout Voltage
Disable Voltage High
Disable Voltage Low
Disable Bias Current High
Disable Bias Current Low
Quiescent Current
Symbol
Vo
Rload
Rline
RR
Vdrop
VdisH
VdisL
IdisH
IdisL
Iq
5mA < Io < 2A
13V < Vin < 29V
note1
Io = 2A
Output Active
Output Disabled
Vdis = 2.7V
Vdis = 0.4V
Io = 0A
Conditions
-
Min.
11.7
-
-
45
-
2.0
-
-
-
-
Typ.
12
0.1
0.5
55
-
-
-
-
-
-
Max.
12.3
2.0
2.5
-
0.5
-
0.8
20
-0.4
10
Unit
V
%
%
dB
V
V
V
µA
mA
mA
Note:
1. These parameters, although guaranteed, are not 100% tested in production.
2. Junction -to -case thermal resistance test enviroments.
-. Pneumatic heat sink fixture.
-. Clamping pressure 60psi through 12mm diameter cylinder.
-. Thermal grease applied between PKG and heat sink fixture
2
KA278R12
Typical Perfomance Characteristics
50
Output voltage Vo(V)
Quiescent current Iq(mA)
15.0
12.5
RL=
40
10.0
RL=
6Ω
8
30
7.5
5.0
2.5
0
0
5
10
15
20
25
20
RL=
0
0
5
10
8
10
15
20
25
Input voltage Vin (V)
Input voltage Vin (V)
Figure 1. Output Voltage vs. Input Voltage
Figure 2. Quiescent Current vs. Input Voltage
Output voltage Vo(V)
12.5
10.0
7.5
5.0
2.5
0
0
0.5
1
1.5
2
2.5
3
Output voltage Vo(V)
15.0
12.04
12.02
12.00
11.98
11.96
11.94
11.92
-25
0
Disable voltage Vdis (V)
75
25
50
TEMPERATURE Tj(
o
C)
100
125
Figure 3. Output Voltage vs. Disable Voltage
Figure 4. Output Voltage vs. Temperature(Tj)
Quiescent current Iq(mA)
Dropout voltage Vdrop(V)
10
8
0.6
0.5
0.4
Io=2A
0.3
1.5A
0.2
1.0A
0.1
0.5A
0
-25
0
25
50
6
4
2
0
-25
0
25
50
75
100
o
125
75
100
o
125
Junction temperature Tj( C)
Junction temperature Tj( C)
Figure 5. Quiescent Current vs. Temperature(Tj)
Figure 6. Dropout Voltage vs. Junction Temperature
3
KA278R12
Typical Perfomance Characteristics
(Continued)
20
100
Power dissipation P
D
(W)
Relative output voltage(%)
80
60
15
10
40
5
20
0
-25
0
0
75
25
50
100
o
TEMPERATURE Ta(°C)
TEMPERATURE Tj( C)
125
0
1.0
2.0
3.0
4.0
5.0
6.0
Output Current(A)
Figure 7. Power Dissipation vs. Temperature(Ta)
Figure 8. Overcurrent Protection Characteristics
(Typical Value)
4
KA278R12
Typical Application
Vin
1
+
Vo
2
+
3
GND
4
Vdis
Disable Signal
Figure 1. Application Circuit
• Ci is required if regulator is located an appreciable distance from power supply filter.
• Co improves stability and transient response.(Co > 47µF)
5
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