Fairchild KA278RXXC service manual
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KA278RXXC-Series
2A Output Low Dropout Volta ge Regulators
Features
KA278RXXC-series (33/05/51/09/12)
• 2A/3.3V, 5V, 5.1V, 9V, 12V output low dropout voltage
regulator
• TO-220 full-mold package (4pin)
• Overcurrent protection, thermal shutdown
• Overvoltage protection, short circuit protection
• With output disable function
KA278RA05C
• Nominal 5V output without adjusting
• Output adjustable between 1.25V and 32V
• 2A output low dropout voltage regulator
• TO-220 full-mold package (4pin)
• Overcurrent protection, thermal shutdown
• Overvoltage protection, short circuit protection
Internal Block Diagram
Description
The KA278RXXC is a low-dropout voltage regulator suitable for various electronic equipments. It provides
constant voltage power source with TO-220-4 lead full mold
package. The dropout voltage of KA278RXXC is below
0.5V in full rated current(2A). This regulator has various
functions such as a peak current protection, a thermal shut
down, an overvoltage protection .
TO-220F-4L
1
1.Vin 2. Vo 3. GND 4. Vdis - KA278RXXC(33/05/51/09/12)
1.Vin 2. Vo 3. GND 4. Vadj - KA278RA05C
1
Vin
THERMAL SHUTDOWN
BANDGAP REFERENCE
HIGH / LOW OUTPUT
4
Vdis
1.4V
ON / OFF
+
OVERVOLTAGE
PROTECTION
+
SOA PROTECTION
SHORTCIRCUIT
PROTECTION
3
GND
(KA278R33/05/51/09/12C)
©2005 Fairchild Semiconductor Corporation
Q1
R1
R2
Vin
2
1
Vo
THERMAL SHUTDOWN
BANDGAP REFERENCE
OVERVOLTAGE
PROTECTION
-
+
SOA PROTECTION
SHORTCIRCUIT
PROTECTION
3
GND
Q1
2
Vo
Rin
4
Vadj
Rref
(KA278RA05C)
Rev. 1.0.2
KA278RXXC-SERIES
Absolute Maximum Ratings
KA278RXXC, KA278RA05C
Parameter Symbol Value Unit Remark
Input voltage Vin 35 V Disable voltage KA278RXXC 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 -
2
KA278RXXC-SERIES
Electrical Characteristics
(Vin=Note3, Io=1.0A, Ta=25°C , unless otherwise specified)
Parameter Symbol Conditions Min. Typ. Max. Unit
KA278R33C
KA278R05C - 4.88 5 5.12
Output voltage
KA278R51C - 4.98 5.1 5.22
Vo
KA278R09C - 8.78 9 9.22
KA278R12C - 11.7 12 12.3
Load regulation Rload 5mA < Io < 2A - 0.1 2.0 %
Line regulation Rline Note4 - 0.5 2.5 %
Ripple rejection ratio RR Note1 45 55 - dB
Dropout voltage Vdrop Io = 2A - - 0.5 V
Disable voltage high KA278RXXC VdisH Output active 2.0 - - V
Disable voltage low KA278RXXC VdisL Output disabled - - 0.8 V
Disable bias current high KA278RXXC IdisH Vdis = 2.7V - - 20 µA
Disable bias current low KA278RXXC IdisL Vdis = 0.4V - - -0.4 mA
Quiescent current Iq Io = 0A - - 10 mA
Reference voltage KA278RA05C Vref - 1.24 1.27 1.30 V
- 3.22 3.3 3.38
V
Note:
1.These parameters, although guaranteed, are not 100% tested in production.
2. Junction -to -case thermal resistance test environments.
-. Pneumati c heat sink fixture.
-. Clamping pressure 60psi through 12mm diameter cyl inder.
-. Thermal grease applied between PKG and heat sink fixt ure.
3. KA278R33C : Vin = 5V
KA278R05C : Vin = 7V
KA278R09C : Vin = 11V
KA278R12C : Vin = 15V
4. KA278R33C : Vin =4 to 10V
KA278R05C, KA278R51C : Vin=6 to 12V
KA278R09C : Vin=10 to 25V
KA278R12C : Vin = 13V to 29V
3
KA278RXXC-SERIES
Typical Performance Characteristics
KA278R33C
5.25
4.50
3.75
8
RL=
RL=3.3Ω
0 2 4 6 8 10
Output voltage Vo(V)
3.00
2.25
1.50
0.75
0
Input voltage Vin (V)
Figure 1. Output Voltage vs. Input Voltage
5.25
4.50
3.75
3.00
2.25
1.50
Output vol tage Vo(V)
0.75
0
0
0.5
1.5
122.5
Disable voltage Vdis (V)
100
80
60
40
20
Quiesce nt current Iq(mA)
0
0 5 10 15 20
Input voltage Vin(V)
RL=
∞
Figure 2. Quiescent Current vs. Input Voltage
3.36
3.34
3.32
3.30
3.28
3.26
Output voltage Vo(V)
3.24
3
3.22
-25
02550
TEMPERATURE Tj(oC)
75
100
125
Figure 3. Output Voltage vs. Disable Voltage
10
8
6
4
2
Quiescent current Iq(mA)
0
02550
-25
75
100
Junction temperature Tj(oC)
Figure 5. Quiescent Current vs. Temperature(Tj)
4
125
Figure 4. Out p ut Voltage vs. Temperature( Tj)
0.70
0.65
0.60
0.55
0.50
0.45
0.40
Drop out voltage Vdrop [V]
0.35
0.30
-25 0 25 50 75 100 125
Junction Temp Tj [
2.0A
!!!!
]
Figure 6. Dropout Voltage vs.Junction Temperature
KA278RXXC-SERIES
Typical Performance Characteristics
20
(W)
D
15
10
5
Power dissipation P
0
-25
02550
TEMPERATURE Tj(oC)
Figure 7. Power Dissipation vs. Temperature(Tj)
4.75
4.50
4.25
75
100
125
(Continued)
100
100
100
80
80
80
60
60
60
40
40
40
20
20
20
Relative output voltage(%)
Relative output voltage(%)
Relative output voltage(%)
0
0
0
01.02.0
01.02.0
01.02.0
3.0
3.0
3.0
4.0
4.0
4.0
Output Current(A)
Output Current(A)
5.0
5.0
5.0
6.0
6.0
6.0
Figure 8. Overcurren t Pro tection Character i st ics
(Typical Value)
4.00
3.75
Output peak current Iop (A)
3.50
0123456
Input-output differential voltage Vin-Vo (V)
Figure 9. Output Peak Currenrt vs.
Input-Output Differential Voltage
5
KA278RXXC-SERIES
Typical Performance Characteristics
KA278R05C
7
6
5
4
3
2
Output voltage Vo(V)
1
0
0
Figure 1. Output Voltage vs. Input Voltage
7
6
5
4
3
2
Output voltage Vo(V)
1
8
RL=
RL=2.5
Ω
51015
Input voltage Vin (V)
(Continued)
120
100
80
60
40
20
Quiesc en t cu rr en t Iq (mA)
0
0 5 10 15 20
Input voltage Vin(V)
RL=
∞
Figure 2. Quiescent Current vs. Input Voltage
5.06
5.04
5.02
5.00
4.98
4.96
Output voltage Vo(V)
4.94
0
0.5
0
1.5
122.5
3
Disable voltage Vdis (V)
Figure 3. Output Voltage vs. Disable Voltage
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)
4.92
-25
02550
TEMPERATURE Tj(oC)
75
100
125
Figure 4. Output Voltage vs. Temperature(Tj)
0.70
0.65
0.60
0.55
0.50
0.45
0.40
Drop out voltage Vdrop [V]
0.35
0.30
-25 0 25 50 75 100 125
Junction Temp Tj [
2.0A
!!!!
]
Figure 6. Dropout Voltage vs.Junction Temperature
6
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