LM7912CT中文资料
TL H 7340LM79XX Series 3-Terminal Negative Regulators
November1994
LM79XX Series3-Terminal Negative Regulators
General Description
The LM79XX series of3-terminal regulators is available with
fixed output voltages of b5V b8V b12V and b15V
These devices need only one external component a com-
pensation capacitor at the output The LM79XX series is
packaged in the TO-220power package and is capable of
supplying1 5A of output current
These regulators employ internal current limiting safe area
protection and thermal shutdown for protection against vir-
tually all overload conditions
Low ground pin current of the LM79XX series allows output
voltage to be easily boosted above the preset value with a
resistor divider The low quiescent current drain of
these devices with a specified maximum change with line
and load ensures good regulation in the voltage boosted
mode
For applications requiring other voltages see LM137data
sheet
Features
Y Thermal short circuit and safe area protection
Y High ripple rejection
Y1 5A output current
Y4%tolerance on preset output voltage Connection Diagrams
TO-220Package
TL H 7340–14
Front View
Order Number LM7905CT LM7912CT or LM7915CT
See NS Package Number TO3B
Typical Applications
Fixed Regulator
TL H 7340–3
Required if regulator is separated from filter capacitor by
more than3 For value given capacitor must be solid
tantalum 25m F aluminum electrolytic may be substituted
Required for stability For value given capacitor must be
solid tantalum 25m F aluminum electrolytic may be substi-
tuted Values given may be increased without limit
For output capacitance in excess of100m F a high current
diode from input to output(1N4001 etc )will protect the
regulator from momentary input shorts
C1995National Semiconductor Corporation RRD-B30M115 Printed in U S A
Absolute Maximum Ratings (Note 1)
If Military Aerospace specified devices are required please contact the National Semiconductor Sales Office Distributors for availability and specifications Input Voltage (V o e b 5V)
b 25V (V o e b 12V and b 15V)
b 35V
Input-Output Differential (V o e b 5V)
25V (V o e b 12V and b 15V)30V
Power Dissipation (Note 2)
Internally Limited
Operating Junction Temperature Range 0 C to a 125 C
Storage Temperature Range
b 65 C to a 150 C Lead Temperature (Soldering 10se
c )
230 C
Electrical Characteristics Conditions unless otherwise noted I OUT e 500mA C IN e 2 2m F C OUT e 1m F
0 C s T J s a 125 C Power Dissipation s 1 5W
Part Number LM7905C
Units
Output Voltage
b 5V Input Voltage (unless otherwise specified)
b 10V
Symbol Parameter Conditions
Min
Typ
Max
V O
Output Voltage
T J e 25 C
b 4 8b 5 0
b 5 2V 5mA s I OUT s 1A b 4 75
b 5 25
V P s 15W
(b 20s V IN s b 7)V D V O
Line Regulation
T J e 25 C (Note 3)
8
50mV (b 25s V IN s b 7)
V 215
mV (b 12s V IN s b 8)
V D V O
Load Regulation
T J e 25 C (Note 3)5mA s I OUT s 1 5A
15100mV 250mA s I OUT s 750mA 550mV I Q Quiescent Current T J e 25 C 1
2mA D I Q
Quiescent Current With Line
0 5
mA Change
(b 25s V IN s b 7)
V With Load 5mA s I OUT s 1A
0 5
mA V n Output Noise Voltage T A e 25 C 10Hz s f s 100Hz 125
m V Ripple Rejection f e 120Hz
54
66
dB (b 18s V IN s b 8)
V Dropout Voltage
T J e 25 C I OUT e 1A 1 1V I OMAX
Peak Output Current T J e 25 C 2 2A Average Temperature I OUT e 5mA 0 4
mV C
Coefficient of 0C s T J s 100 C
Output Voltage
Typical Applications (Continued)
Variable Output
TL H 7340–2
Improves transient response and ripple rejection Do not increase beyond 50m F V OUT e V SET
R1a R2R2J
Select R2as follows
LM7905CT 300X LM7912CT 750X LM7915CT
1k
2
Electrical Characteristics (Continued)Conditions unless otherwise noted I OUT e 500mA C IN e 2 2m F C OUT e 1m F 0 C s T J s a 125 C Power Dissipation e 1 5W
Part Number LM7912C
LM7915C
Units
Output Voltage
b 12V b 15V Input Voltage (unless otherwise specified)
b 19V
b 23V
Symbol Parameter Conditions
Min
Typ Max Min Typ
Max
V O
Output Voltage
T J e 25 C
b 11 5b 12 0b 12 5b 14 4b 15 0b 15 6
V 5mA s I OUT s 1A b 11 4b 12 6
b 14 25b 15 75
V P s 15W
(b 27s V IN s b 14 5)(b 30s V IN s b 17 5)
V D V O
Line Regulation
T J e 25 C (Note 3)
580
5100
mV (b 30s V IN s b 14 5)
(b 30s V IN s b 17 5)
V 330350mV (b 22s V IN s b 16)
(b 26s V IN s b 20)
V D V O
Load Regulation
T J e 25 C (Note 3)
5mA s I OUT s 1 5A
1520015200mV 250mA s I OUT s 750mA 575575mV I Q Quiescent Current T J e 25 C 1 5
31 5
3mA D I Q
Quiescent Current With Line
0 5
0 5
mA Change
(b 30s V IN s b 14 5)
(b 30s V IN s b 17 5)
V With Load 5mA s I OUT s 1A
0 5
0 5
mA V n Output Noise Voltage T A e 25 C 10Hz s f s 100Hz 300
375
m V Ripple Rejection f e 120Hz
5470
5470
dB (b 25s V IN s b 15)
(b 30s V IN s b 17 5)
V Dropout Voltage
T J e 25 C I OUT e 1A 1 11 1V I OMAX
Peak Output Current T J e 25 C 2 2
2 2
A Average Temperature I OUT e 5mA b 0 8
b 1 0
mV C
Coefficient of 0C s T J s 100 C
Output Voltage
Note 1 Absolute Maximum Ratings indicate limits beyond which damage to the device may occur Operating Ratings indicate conditions for which the device is intended to be functional but do not guarantee Specific Performance limits For guaranteed specifications and test conditions see the Electrical Characteristics Note 2 Refer to Typical Performance Characteristics and Design Considerations for details
Note 3 Regulation is measured at a constant junction temperature by pulse testing with a low duty cycle Changes in output voltage due to heating effects must be taken into account
Typical Applications (Continued)
Dual Trimmed Supply
TL H 7340–4
3
Design Considerations
The LM79XX fixed voltage regulator series has thermal
overload protection from excessive power dissipation inter-
nal short circuit protection which limits the circuit’s maxi-
mum current and output transistor safe-area compensation
for reducing the output current as the voltage across the
pass transistor is increased
Although the internal power dissipation is limited the junc-
tion temperature must be kept below the maximum speci-
fied temperature(125 C)in order to meet data sheet specifi-cations To calculate the maximum junction temperature or
heat sink required the following thermal resistance values
should be used
Typ Max Typ Max Package i JC i JC i JA i JA
C W C W C W C W
TO-2203 05 06040
P D MAX e T J Max b T A
i JC a i CA
or
T J Max T A
i JA
i CA e i CS a i SA(without heat sink) Solving for T J
T J e T A a P D(i JC a i CA)or
e T A a P D i JA(without heat sink)
Where
T J e Junction Temperature
T A e Ambient Temperature
P D e Power Dissipation
i JA e Junction-to-Ambient Thermal Resistance
i JC e Junction-to-Case Thermal Resistance
i CA e Case-to-Ambient Thermal Resistance
i CS e Case-to-Heat Sink Thermal Resistance
i SA e Heat Sink-to-Ambient Thermal Resistance
Typical Applications(Continued)
Bypass capacitors are necessary for stable operation of the
LM79XX series of regulators over the input voltage and out-
put current ranges Output bypass capacitors will improve
the transient response by the regulator
The bypass capacitors (2 2m F on the input 1 0m F on the
output)should be ceramic or solid tantalum which have
good high frequency characteristics If aluminum electrolyt-
ics are used their values should be10m F or larger The
bypass capacitors should be mounted with the shortest
leads and if possible directly across the regulator termi-
nals
High Stability1Amp Regulator
TL H 7340–5
Load and line regulation k0 01%temperature stability s0 2%
Determine Zener current
Solid tantalum
Select resistors to set output voltage 2ppm C tracking suggested
4
Typical Applications (Continued)
Current Source
I OUT e 1mA a
5V R1
TL H 7340–7
Light Controller Using Silicon Photo Cell
TL H 7340–8
Lamp brightness increase until i I e i Q ( 1mA)a 5V R1
Necessary only if raw supply filter capacitor is more than 2 from LM7905CT
5
Typical Applications(Continued)
High-Sensitivity Light Controller
TL H 7340–9
Lamp brightness increases until i i e5V R1(I i can be set as low as1m A)
Necessary only if raw supply filter capacitor is more than2 from LM7905
g15V 1Amp Tracking Regulators
TL H 7340–1
(b15)(a15)
Load Regulation at D I L e1A40mV2mV
Output Ripple C IN e3000m F I L e1A100m Vrms100m Vrms
Temperature Stability50mV50mV
Output Noise10Hz s f s10kHz150m Vrms150m Vrms
Resistor tolerance of R4and R5determine matching of(a)and(b)
outputs
Necessary only if raw supply filter capacitors are more than3 from regu-
lators
6
Schematic Diagrams
b 5V
T L H 7340–12
7
Schematic Diagrams (Continued)
b 12V a n d b 15V
T L H 7340–13
8
9
L M 79X X S e r i e s 3-T e r m i n a l N e g a t i v e R e g u l a t o r s
Physical Dimensions inches (millimeters)
TO-220Outline Package (T)
Order Number LM7905CT LM7912CT or LM7915CT
NS Package Number T03B
LIFE SUPPORT POLICY
NATIONAL’S PRODUCTS ARE NOT AUTHORIZED FOR USE AS CRITICAL COMPONENTS IN LIFE SUPPORT DEVICES OR SYSTEMS WITHOUT THE EXPRESS WRITTEN APPROVAL OF THE PRESIDENT OF NATIONAL SEMICONDUCTOR CORPORATION As used herein 1 Life support devices or systems are devices or 2 A critical component is any component of a life systems which (a)are intended for surgical implant support device or system whose failure to perform can into the body or (b)support or sustain life and whose be reasonably expected to cause the failure of the life failure to perform when properly used in accordance support device or system or to affect its safety or with instructions for use provided in the labeling can effectiveness
be reasonably expected to result in a significant injury to the user
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