Fairchild Semiconductor KA278R12 Datasheet
KA278R12
Low Dropout Voltage Regulator
www.fairchildsemi.com
Features
• 2A / 12V Output low dropout voltage regulator
• TO220 Full-Mold package (4PIN)
• Overcurrent protection, T hermal shutdow n
• Overvoltag e protection, Short-Circuit protection
• With output disable function
Internal Block Diagram
1
Vin
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. Dr opout voltage of K A278R12 is belo w 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
Q1
2
Vo
THERMAL SHUTDOWN
BANDGAP REFERENCE
HIGH / LOW OUTPUT
4
Vdis
1.4V
©2001 Fairchild Semiconductor Corporation
+
ON / OFF
OVERVOLTAGE
PROTECTION
+
SOA PROTECTION
SHORT-CIRCUIT
SHORTCIRCUIT
PROTECTION
3
GND
R1
R2
Rev. 1.0.2
KA278R12
Absolute Maximum Ratings
Parameter Symbol Value Unit Remark
Input Voltage Vin 35 V Disable Voltage Vdis 35 V Output Current Io 2.0 A Power Dissipation 1 Pd1 1.5 W No Heatsink
Power Dissipation 2 Pd2 15 W With Heatsink
Junction Temperature Tj 150 °C-
Operating Temperature Topr -20~80 °C-
Thermal Resistance, Junction-to Case (Note2) Rθjc 2.9 °C/W -
Thermal Resistance, Junction-to-Air (Note2) Rθja 48.51 °C/W -
Thermal Shutdown Temperature Ttsd 150 °C-
Electrical Characteristics
(Vin=15V, Io=1.0A, Ta=25°C , unless otherwise specified)
Parameter Symbol Conditions Min. Typ. Max. Unit
Output Voltage Vo - 11.7 12 12.3 V
Load Regulation Rload 5mA < Io < 2A - 0.1 2.0 %
Line Regulation Rline 13V < Vin < 29V - 0.5 2.5 %
Ripple Rejection Ratio RR note1 45 55 - dB
Dropout Voltage Vdrop Io = 2A - - 0.5 V
Disable Voltage High VdisH Output Active 2.0 - - V
Disable Voltage Low VdisL Output Disabled - - 0.8 V
Disable Bias Current High IdisH Vdis = 2.7V - - 20 µA
Disable Bias Current Low IdisL Vdis = 0.4V - - -0.4 mA
Quiescent Current Iq Io = 0A - - 10 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 cyl inder.
-. Thermal gr ease applied be tween PKG and h eat sink fixtur e
2
Typical Perfomance Characteristics
15.0
Output voltage Vo(V)
12.5
10.0
7.5
5.0
2.5
RL=
8
RL= 6Ω
KA278R12
50
40
30
20
10
Quiescent current Iq(mA)
RL=
8
0
51015
0
20 25
Input voltage Vin (V)
Figure 1. Output Voltage vs. Input Voltage
15.0
12.5
10.0
7.5
5.0
Output voltage Vo(V)
2.5
0
0
0.5
122.5
1.5
3
Disable voltage Vdis (V)
Figure 3. Output Voltage vs. Disable Voltage
0
5101520 25
0
Input voltage Vin (V)
Figure 2. Quiescent Current vs. Input Voltage
12.04
12.02
12.00
11.98
11.96
Output voltage Vo(V)
11.94
11.92
02550
-25
75
100
125
TEMPERATURE Tj(oC)
Figure 4. Output Voltage vs. Temper at ure(Tj)
10
8
6
4
2
Quiescent current Iq (mA)
0
02550
-25
75
100
125
Junction temperature Tj(oC)
Figure 5. Quiescent Current vs. Temperature(Tj)
0.6
0.5
0.4
0.3
0.2
Dropout voltage Vdrop (V)
0.1
0
02550
-25
Io=2A
1.5A
1.0A
0.5A
75
100
125
Junction temperature Tj(oC)
Figure 6. Dropout Voltage vs. Junction Temperature
3
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