LM2940/LM2940C
1A Low Dropout Regulator
General Description
The LM2940/LM2940C positive voltage regulator features
the ability to source 1A of output current with a dropout volt-
age of typically 0.5V and a maximum of 1V over the entire
temperature range. Furthermore, a quiescent current reduc-
tion circuit has been included which reduces the ground cur-
rent when the differential between the input voltage and the
output voltage exceeds approximately 3V. The quiescent
current with 1A of output current and an input-output differ-
ential of 5V is therefore only 30 mA. Higher quiescent cur-
rents only exist when the regulator is in the dropout mode
(V
IN
−V
OUT
≤3V).
Designed also for vehicular applications, the LM2940/
LM2940C and all regulated circuitry are protected from re-
verse battery installations or 2-battery jumps. During line
transients, such as load dump when the input voltage can
momentarily exceed the specified maximum operating volt-
age, the regulator will automatically shut down to protect
both the internal circuits and the load. The LM2940/
LM2940C cannot be harmed by temporary mirror-image in-
sertion. Familiar regulator features such as short circuit and
thermal overload protection are also provided.
Features
nDropout voltage typically 0.5V @I
O
=1A
nOutput current in excess of 1A
nOutput voltage trimmed before assembly
nReverse battery protection
nInternal short circuit current limit
nMirror image insertion protection
nP
+
Product Enhancement tested
Typical Application
Ordering Information
Temperature
Range Output Voltage Package
5.0 8.0 9.0 10 12 15
0˚C ≤TJ≤125˚C LM2940CT-5.0 LM2940CT-9.0 LM2940CT-12 LM2940CT-15 TO-220
LM2940CS-5.0 LM2940CS-9.0 LM2940CS-12 LM2940CS-15 TO-263
−40˚C ≤TJ≤125˚C LM2940T-5.0 LM2940T-8.0 LM2940T-9.0 LM2940T-10 LM2940T-12 TO-220
LM2940S-5.0 LM2940S-8.0 LM2940S-9.0 LM2940S-10 LM2940S-12 TO-263
−40˚C ≤TJ≤85˚C LM2940IMP-5.0 LM2940IMP-8.0 LM2940IMP-9.0 LM2940IMP-10 LM2940IMP-12 LM2940IMP-15 SOT-223
LM2940IMPX-5.0 LM2940IMPX-8.0 LM2940IMPX-9.0 LM2940IMPX-10 LM2940IMPX-12 LM2940IMPX-15 SOT-223
in Tape
and Reel
SOT-223 Package
Marking L53B L54B L0EB L55B L56B L70B
The physical size of the SOT-223 is too small to contain the full device part number. The package markings indicated are what will appear on the actual device.
Temperature
Range Output Voltage Package
5.0 8.0 12 15
−55˚C ≤TJ≤125˚C LM2940J-5.0/883
5962-8958701EA LM2940J-8.0/883
5962-9088301QEA LM2940J-12/883
5962-9088401QEA LM2940J-15/883
5962-9088501QEA J16A
LM2940WG5.0/883
5962-8958701XA WG16A
For information on military temperature range products, please go to the Mil/Aero Web Site at http://www.national.com/appinfo/milaero/index.html.
DS008822-3
*Required if regulator is located far from power supply filter.
**COUT must be at least 22 µF to maintain stability. May be increased without bound to maintain regulation during transients. Locate as close as possible
to the regulator. This capacitor must be rated over the same operating temperature range as the regulator and the ESR is critical; see curve.
July 2000
LM2940/LM2940C 1A Low Dropout Regulator
© 2000 National Semiconductor Corporation DS008822 www.national.com
Connection Diagrams
(TO-220) Plastic Package
DS008822-2
Front View
Order Number LM2940CT-5.0, LM2940CT-9.0,
LM2940CT-12, LM2940CT-15, LM2940T-5.0,
LM2940T-8.0, LM2940T-9.0,
LM2940T-10 or LM2940T-12
See NS Package Number TO3B
3-Lead SOT-223
DS008822-42
Front View
Order Part Number LM2940IMP-5.0,
LM2940IMP-8.0, LM2940IMP-9.0,
LM2940IMP-10, LM2940IMP-12 or LM2940IMP-15
See NS Package Number MP04A
16-Lead Dual-in-Line Package (J)
DS008822-43
Top View
Order Number LM2940J-5.0/883 (5962-8958701EA),
LM2940J-8.0/883 (5962-9088301QEA),
LM2940J-12/883 (5962-9088401QEA),
LM2940J-15/883 (5962-9088501QEA)
See NS Package Number J16A
16-Lead Ceramic Surface-Mount Package (WG)
DS008822-44
Top View
Order Number LM2940WG5.0/883 (5962-8958701XA)
See NS Package Number WG16A
(TO-263) Surface-Mount Package
DS008822-11
Top View
DS008822-12
Side View
Order Number LM2940CS-5.0, LM2940CS-9.0,
LM2940CS-12, LM2940CS-15,
LM2940S-5.0, LM2940S-8.0,
LM2940S-9.0, LM2940S-10 or LM2940S-12
See NS Package Number TS3B
LM2940/LM2940C
www.national.com 2
Absolute Maximum Ratings (Note 1)
If Military/Aerospace specified devices are required,
please contact the National Semiconductor Sales Office/
Distributors for availability and specifications.
LM2940S, T, MP ≤100 ms 60V
LM2940CS, T ≤1 ms 45V
Internal Power Dissipation
(Note 2) Internally Limited
Maximum Junction Temperature 150˚C
Storage Temperature Range −65˚C ≤T
J
≤+150˚C
Lead Temperature, Time for Wave Soldering
TO-220 (T) Package 260˚C, 10s
TO-263 (S) Package 260˚C, 4s
SOT-223 (MP) Package 260˚C, 4s
ESD Susceptibility (Note 3) 2 kV
Operating Conditions (Note 1)
Input Voltage 26V
Temperature Range
LM2940T, LM2940S −40˚C ≤T
J
≤125˚C
LM2940CT, LM2940CS 0˚C ≤T
J
≤125˚C
LM2940IMP −40˚C ≤T
J
≤85˚C
LM2940J, LM2940WG −55˚C ≤T
J
≤125˚C
Electrical Characteristics
V
IN
=V
O
+ 5V, I
O
= 1A, C
O
= 22 µF, unless otherwise specified. Boldface limits apply over the entire operating tempera-
ture range of the indicated device. All other specifications apply for T
A
=T
J
= 25˚C.
Output Voltage (V
O
)5V 8V
Units
LM2940 LM2940/883 LM2940 LM2940/883
Parameter Conditions Typ Limit Limit Typ Limit Limit
(Note 4) (Note 5) (Note 4) (Note 5)
6.25V ≤V
IN
≤26V 9.4V ≤V
IN
≤26V
Output Voltage 5 mA ≤I
O
≤1A 5.00 4.85/4.75 4.85/4.75 8.00 7.76/7.60 7.76/7.60 V
MIN
5.15/5.25 5.15/5.25 8.24/8.40 8.24/8.40 V
MAX
Line Regulation V
O
+2V≤V
IN
≤26V, 20 50 40/50 20 80 50/80 mV
MAX
I
O
=5mA
Load Regulation 50 mA ≤I
O
≤1A
LM2940, LM2940/883 35 50/80 50/100 55 80/130 80/130 mV
MAX
LM2940C 35 50 55 80
Output 100 mADC and
Impedance 20 mArms, 35 1000/1000 55 1000/1000 mΩ
f
O
= 120 Hz
Quiescent V
O
+2V ≤V
IN
≤26V,
Current I
O
=5mA
LM2940, LM2940/883 10 15/20 15/20 10 15/20 15/20 mA
MAX
LM2940C 10 15
V
IN
=V
O
+ 5V, 30 45/60 50/60 30 45/60 50/60 mA
MAX
I
O
=1A
Output Noise 10 Hz − 100 kHz, 150 700/700 240 1000/1000 µV
rms
Voltage I
O
=5mA
Ripple Rejection f
O
= 120 Hz, 1 V
rms
,
I
O
= 100 mA
LM2940 72 60/54 66 54/48 dB
MIN
LM2940C 72 60 66 54
f
O
= 1 kHz, 1 V
rms
, 60/50 54/48 dB
MIN
I
O
=5mA
Long Term 20 32 mV/
Stability 1000 Hr
Dropout Voltage I
O
= 1A 0.5 0.8/1.0 0.7/1.0 0.5 0.8/1.0 0.7/1.0 V
MAX
I
O
= 100 mA 110 150/200 150/200 110 150/200 150/200 mV
MAX
Short Circuit
Current (Note 6) 1.9 1.6 1.5/1.3 1.9 1.6 1.6/1.3 A
MIN
LM2940/LM2940C
www.national.com3
Electrical Characteristics (Continued)
V
IN
=V
O
+ 5V, I
O
= 1A, C
O
= 22 µF, unless otherwise specified. Boldface limits apply over the entire operating tempera-
ture range of the indicated device. All other specifications apply for T
A
=T
J
= 25˚C.
Output Voltage (V
O
)5V 8V
Units
LM2940 LM2940/883 LM2940 LM2940/883
Parameter Conditions Typ Limit Limit Typ Limit Limit
(Note 4) (Note 5) (Note 4) (Note 5)
Maximum Line R
O
= 100Ω
V
MIN
Transient LM2940, T ≤100 ms 75 60/60 75 60/60
LM2940/883, T ≤20 ms 40/40 40/40
LM2940C, T ≤1ms5545 5545
Reverse Polarity R
O
= 100Ω
DC Input Voltage LM2940, LM2940/883 −30 −15/−15 −15/−15 −30 −15/−15 −15/−15 V
MIN
LM2940C −30 −15 −30 −15
Reverse Polarity R
O
= 100Ω
Transient Input LM2940, T ≤100 ms −75 −50/−50 −75 −50/−50 V
MIN
Voltage LM2940/883, T ≤20 ms −45/−45 −45/−45
LM2940C, T ≤1 ms −55 −45/−45
Electrical Characteristics
V
IN
=V
O
+ 5V, I
O
= 1A, C
O
= 22 µF, unless otherwise specified. Boldface limits apply over the entire operating tempera-
ture range of the indicated device. All other specifications apply for T
A
=T
J
= 25˚C.
Output Voltage (V
O
) 9V 10V
Units
Parameter Conditions Typ LM2940 Typ LM2940
Limit Limit
(Note 4) (Note 4)
10.5V ≤V
IN
≤26V 11.5V ≤V
IN
≤26V
Output Voltage 5 mA ≤I
O
≤1A 9.00 8.73/8.55 10.00 9.70/9.50 V
MIN
9.27/9.45 10.30/10.50 V
MAX
Line Regulation V
O
+2V≤V
IN
≤26V, 20 90 20 100 mV
MAX
I
O
=5mA
Load Regulation 50 mA ≤I
O
≤1A
LM2940 60 90/150 65 100/165 mV
MAX
LM2940C 60 90
Output Impedance 100 mADC and
20 mArms, 60 65 mΩ
f
O
= 120 Hz
Quiescent V
O
+2V ≤V
IN
<26V,
Current I
O
=5mA
LM2940 10 15/20 10 15/20 mA
MAX
LM2940C 10 15
V
IN
=V
O
+ 5V, I
O
= 1A 30 45/60 30 45/60 mA
MAX
Output Noise 10 Hz − 100 kHz, 270 300 µV
rms
Voltage I
O
=5mA
Ripple Rejection f
O
= 120 Hz, 1 V
rms
,
I
O
= 100 mA
LM2940 64 52/46 63 51/45 dB
MIN
LM2940C 64 52
Long Term
Stability 34 36 mV/
1000 Hr
Dropout Voltage I
O
= 1A 0.5 0.8/1.0 0.5 0.8/1.0 V
MAX
I
O
= 100 mA 110 150/200 110 150/200 mV
MAX
LM2940/LM2940C
www.national.com 4
Electrical Characteristics (Continued)
V
IN
=V
O
+ 5V, I
O
= 1A, C
O
= 22 µF, unless otherwise specified. Boldface limits apply over the entire operating tempera-
ture range of the indicated device. All other specifications apply for T
A
=T
J
= 25˚C.
Output Voltage (V
O
) 9V 10V
Units
Parameter Conditions Typ LM2940 Typ LM2940
Limit Limit
(Note 4) (Note 4)
Short Circuit (Note 6) 1.9 1.6 1.9 1.6 A
MIN
Current
Maximum Line R
O
= 100Ω
Transient T ≤100 ms
LM2940 75 60/60 75 60/60 V
MIN
LM2940C 55 45
Reverse Polarity R
O
= 100Ω
DC Input Voltage LM2940 −30 −15/−15 −30 −15/−15 V
MIN
LM2940C −30 −15
Reverse Polarity R
O
= 100Ω
Transient Input T ≤100 ms
Voltage LM2940 −75 −50/−50 −75 −50/−50 V
MIN
LM2940C −55 −45/−45
Electrical Characteristics
V
IN
=V
O
+ 5V, I
O
= 1A, C
O
= 22 µF, unless otherwise specified. Boldface limits apply over the entire operating tempera-
ture range of the indicated device. All other specifications apply for T
A
=T
J
= 25˚C.
Output Voltage (V
O
) 12V 15V
Units
LM2940 LM2940/833 LM2940 LM2940/833
Parameter Conditions Typ Limit Limit Typ Limit Limit
(Note 4) (Note 5) (Note 4) (Note 5)
13.6V ≤V
IN
≤26V 16.75V ≤V
IN
≤26V
Output Voltage 5 mA ≤I
O
≤1A 12.00 11.64/11.40 11.64/11.40 15.00 14.55/14.25 14.55/14.25 V
MIN
12.36/12.60 12.36/12.60 15.45/15.75 15.45/15.75 V
MAX
Line Regulation V
O
+2V≤V
IN
≤26V, 20 120 75/120 20 150 95/150 mV
MAX
I
O
=5mA
Load Regulation 50 mA ≤I
O
≤1A
LM2940, LM2940/883 55 120/200 120/190 150/240 mV
MAX
LM2940C 55 120 70 150
Output 100 mADC and
Impedance 20 mArms, 80 1000/1000 100 1000/1000 mΩ
f
O
= 120 Hz
Quiescent
Current V
O
+2V ≤V
IN
≤26V,
I
O
=5mA
LM2940, LM2940/883 10 15/20 15/20 15/20 mA
MAX
LM2940C 10 15 10 15
V
IN
=V
O
+ 5V, I
O
= 1A 30 45/60 50/60 30 45/60 50/60 mA
MAX
Output Noise 10 Hz − 100 kHz, 360 1000/1000 450 1000/1000 µV
rms
Voltage I
O
=5mA
Ripple Rejection f
O
= 120 Hz, 1 V
rms
,
I
O
= 100 mA
LM2940 66 54/48 dB
MIN
LM2940C 66 54 64 52
f
O
= 1 kHz, 1 V
rms
,52/46 48/42 dB
MIN
I
O
=5mA
LM2940/LM2940C
www.national.com5
Electrical Characteristics (Continued)
V
IN
=V
O
+ 5V, I
O
= 1A, C
O
= 22 µF, unless otherwise specified. Boldface limits apply over the entire operating tempera-
ture range of the indicated device. All other specifications apply for T
A
=T
J
= 25˚C.
Output Voltage (V
O
) 12V 15V
Units
LM2940 LM2940/833 LM2940 LM2940/833
Parameter Conditions Typ Limit Limit Typ Limit Limit
(Note 4) (Note 5) (Note 4) (Note 5)
Long Term 48 60 mV/
Stability 1000 Hr
Dropout Voltage I
O
= 1A 0.5 0.8/1.0 0.7/1.0 0.5 0.8/1.0 0.7/1.0 V
MAX
I
O
= 100 mA 110 150/200 150/200 110 150/200 150/200 mV
MAX
Short Circuit (Note 6) 1.9 1.6 1.6/1.3 1.9 1.6 1.6/1.3 A
MIN
Current
Maximum Line R
O
= 100Ω
Transient LM2940, T ≤100 ms 75 60/60
LM2940/883, T ≤20 ms 40/40 40/40 V
MIN
LM2940C, T ≤1ms5545 5545
Reverse Polarity R
O
= 100Ω
DC Input LM2940, LM2940/883 −30 −15/−15 −15/−15 −15/−15 V
MIN
Voltage LM2940C −30 −15 −30 −15
Reverse Polarity R
O
= 100Ω
Transient Input LM2940, T ≤100 ms −75 −50/−50
Voltage LM2940/883, T ≤20 ms −45/−45 −45/−45 V
MIN
LM2940C, T ≤1 ms −55 −45/−45 −55 −45/−45
Note 1: Absolute Maximum Ratings are limits beyond which damage to the device may occur. Operating Conditions are conditions under which the device functions
but the specifications might not be guaranteed. For guaranteed specifications and test conditions see the Electrical Characteristics.
Note 2: The maximum allowable power dissipation is a function of the maximum junction temperature, TJ, the junction-to-ambient thermal resistance, θJ−A, and the
ambient temperature, TA. Exceeding the maximum allowable power dissipation will cause excessive die temperature, and the regulator will go into thermal shutdown.
The value of θJ−A (for devices in still air with no heatsink) is 60˚C/W for the TO-220 package, 80˚C/W for theTO-263 package, and 174˚C/W for the SOT-223 package.
The effective value of θJ−A can be reduced by using a heatsink (seeApplication Hints for specific information on heatsinking). The values of θJ−A and θJ−Cfor the K02A
package are 39˚C/W and 4˚C/W respectively.
Note 3: ESD rating is based on the human body model, 100 pF discharged through 1.5 kΩ.
Note 4: All limits are guaranteed at TA=T
J= 25˚C only (standard typeface) or over the entire operating temperature range of the indicated device (boldface type).
All limits at TA=T
J= 25˚C are 100% production tested. All limits at temperature extremes are guaranteed via correlation using standard Statistical Quality Control
methods.
Note 5: All limits are guaranteed at TA=T
J= 25˚C only (standard typeface) or over the entire operating temperature range of the indicated device (boldface type).
All limits are 100% production tested and are used to calculate Outgoing Quality Levels.
Note 6: Output current will decrease with increasing temperature but will not drop below 1A at the maximum specified temperature.
Typical Performance Characteristics
Dropout Voltage
DS008822-13
Dropout Voltage
vs Temperature
DS008822-14
Output Voltage
vs Temperature
DS008822-15
LM2940/LM2940C
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Typical Performance Characteristics (Continued)
Quiescent Current
vs Temperature
DS008822-16
Quiescent Current
DS008822-17
Quiescent Current
DS008822-18
Line Transient Response
DS008822-19
Load Transient Response
DS008822-20
Ripple Rejection
DS008822-21
Low Voltage Behavior
DS008822-25
Low Voltage Behavior
DS008822-26
Low Voltage Behavior
DS008822-27
Low Voltage Behavior
DS008822-28
Low Voltage Behavior
DS008822-29
Low Voltage Behavior
DS008822-30
LM2940/LM2940C
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Typical Performance Characteristics (Continued)
Output at
Voltage Extremes
DS008822-31
Output at
Voltage Extremes
DS008822-32
Output at
Voltage Extremes
DS008822-33
Output at
Voltage Extremes
DS008822-34
Output at
Voltage Extremes
DS008822-35
Output at
Voltage Extremes
DS008822-36
Output Capacitor ESR
DS008822-6
Peak Output Current
DS008822-8
LM2940/LM2940C
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Typical Performance Characteristics (Continued)
Output Impedance
DS008822-22
Maximum Power
Dissipation (TO-220)
DS008822-23
Maximum Power
Dissipation (TO-3)
DS008822-24
Maximum Power Dissipation
(TO-263) See (Note 2)
DS008822-10
LM2940/LM2940C
www.national.com9
Equivalent Schematic Diagram
Application Hints
EXTERNAL CAPACITORS
The output capacitor is critical to maintaining regulator stabil-
ity, and must meet the required conditions for both ESR
(Equivalent Series Resistance) and minimum amount of ca-
pacitance.
MINIMUM CAPACITANCE:
The minimum output capacitance required to maintain stabil-
ity is 22 µF (this value may be increased without limit).
Larger values of output capacitance will give improved tran-
sient response.
ESR LIMITS:
The ESR of the output capacitor will cause loop instability if
it is too high or too low. The acceptable range of ESR plotted
versus load current is shown in the graph below.
It is essen-
tial that the output capacitor meet these requirements,
or oscillations can result.
It is important to note that for most capacitors, ESR is speci-
fied only at room temperature. However, the designer must
ensure that the ESR will stay inside the limits shown over the
entire operating temperature range for the design.
For aluminum electrolytic capacitors, ESR will increase by
about 30X as the temperature is reduced from 25˚C to
−40˚C. This type of capacitor is not well-suited for low tem-
perature operation.
Solid tantalum capacitors have a more stable ESR over tem-
perature, but are more expensive than aluminum electrolyt-
ics. A cost-effective approach sometimes used is to parallel
DS008822-1
Output Capacitor ESR
DS008822-6
FIGURE 1. ESR Limits
LM2940/LM2940C
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Application Hints (Continued)
an aluminum electrolytic with a solid Tantalum, with the total
capacitance split about 75/25% with the Aluminum being the
larger value.
If two capacitors are paralleled, the effective ESR is the par-
allel of the two individual values. The “flatter” ESR of the Tan-
talum will keep the effective ESR from rising as quickly at low
temperatures.
HEATSINKING
A heatsink may be required depending on the maximum
power dissipation and maximum ambient temperature of the
application. Under all possible operating conditions, the junc-
tion temperature must be within the range specified under
Absolute Maximum Ratings.
To determine if a heatsink is required, the power dissipated
by the regulator, P
D
, must be calculated.
The figure below shows the voltages and currents which are
present in the circuit, as well as the formula for calculating
the power dissipated in the regulator:
The next parameter which must be calculated is the maxi-
mum allowable temperature rise, T
R
(max). This is calcu-
lated by using the formula:
T
R
(max) = T
J
(max) − T
A
(max)
where: T
J
(max) is the maximum allowable junction tem-
perature, which is 125˚C for commercial
grade parts.
T
A
(max) is the maximum ambient temperature
which will be encountered in the applica-
tion.
Using the calculated values for T
R
(max) and P
D
, the maxi-
mum allowable value for the junction-to-ambient thermal re-
sistance, θ
(J−A)
, can now be found:
θ
(J−A)
=T
R
(max)/P
D
IMPORTANT: If the maximum allowable value for θ
(J−A)
is
found to be ≥53˚C/W for the TO-220 package, ≥80˚C/W for
the TO-263 package, or ≥174˚C/W for the SOT-223 pack-
age, no heatsink is needed since the package alone will dis-
sipate enough heat to satisfy these requirements.
If the calculated value for θ
(J−A)
falls below these limits, a
heatsink is required.
HEATSINKING TO-220 PACKAGE PARTS
The TO-220 can be attached to a typical heatsink, or se-
cured to a copper plane on a PC board. If a copper plane is
to be used, the values of θ
(J−A)
will be the same as shown in
the next section for the TO-263.
If a manufactured heatsink is to be selected, the value of
heatsink-to-ambient thermal resistance, θ
(H−A)
, must first be
calculated: θ
(H−A)
=θ
(J−A)
−θ
(C−H)
−θ
(J−C)
Where: θ
(J−C)
is defined as the thermal resistance from
the junction to the surface of the case. A
value of 3˚C/W can be assumed for θ
(J−C)
for this calculation.
θ
(C−H)
is defined as the thermal resistance be-
tween the case and the surface of the heat-
sink. The value of θ
(C−H)
will vary from
about 1.5˚C/W to about 2.5˚C/W (depend-
ing on method of attachment, insulator,
etc.). If the exact value is unknown, 2˚C/W
should be assumed for θ
(C−H)
.
When a value for θ
(H−A)
is found using the equation shown,
a heatsink must be selected that has a value that is less than
or equal to this number.
θ
(H−A)
is specified numerically by the heatsink manufacturer
in the catalog, or shown in a curve that plots temperature rise
vs power dissipation for the heatsink.
HEATSINKING TO-263 AND SOT-223 PACKAGE PARTS
Both the TO-263 (“S”) and SOT-223 (“MP”) packages use a
copper plane on the PCB and the PCB itself as a heatsink.
To optimize the heat sinking ability of the plane and PCB,
solder the tab of the package to the plane.
Figure 3
shows for the TO-263 the measured values of θ
(J−A)
for different copper area sizes using a typical PCB with 1
ounce copper
and no solder mask over the copper area used
for heatsinking.
As shown in the figure, increasing the copper area beyond 1
square inch produces very little improvement. It should also
be observed that the minimum value of θ
(J−A)
for the TO-263
package mounted to a PCB is 32˚C/W.
As a design aid,
Figure 4
shows the maximum allowable
power dissipation compared to ambient temperature for the
TO-263 device (assuming θ
(J−A)
is 35˚C/W and the maxi-
mum junction temperature is 125˚C).
DS008822-37
IIN =I
L÷I
G
P
D=(V
IN −V
OUT)I
L+(V
IN)I
G
FIGURE 2. Power Dissipation Diagram
DS008822-38
FIGURE 3. θ
(J−A)
vs Copper (1 ounce) Area for the
TO-263 Package
LM2940/LM2940C
www.national.com11
Application Hints (Continued)
Figure 5
and
Figure 6
show the information for the SOT-223
package.
Figure 6
assumes a θ
(J−A)
of 74˚C/W for 1 ounce
copper and 51˚C/W for 2 ounce copper and a maximum
junction temperature of 125˚C.
DS008822-39
FIGURE 4. Maximum Power Dissipation vs T
AMB
for
the TO-263 Package
DS008822-40
FIGURE 5. θ
(J−A)
vs Copper (2 ounce) Area for the
SOT-223 Package
DS008822-41
FIGURE 6. Maximum Power Dissipation vs T
AMB
for
the SOT-223 Package
LM2940/LM2940C
www.national.com 12
Physical Dimensions inches (millimeters) unless otherwise noted
3-Lead SOT-223 Package
Order Part Number LM2940IMP-5.0
LM2940IMP-8.0 LM2940IMP-9.0
LM2940IMP-10 LM2940IMP-12 LM2940IMP-15
NS Package Number MP04A
LM2940/LM2940C
www.national.com13
Physical Dimensions inches (millimeters) unless otherwise noted (Continued)
16 Lead Dual-in-Line Package (J)
Order Number LM2940J-5.0/883 (5962-8958701EA),
LM2940J-8.0/883 (5962-9088301QEA),
LM2940J-12/883 (5962-9088401QEA),
LM2940J-15/883 (5962-9088501QEA)
See NS Package Number J16A
LM2940/LM2940C
www.national.com 14
Physical Dimensions inches (millimeters) unless otherwise noted (Continued)
16 Lead Surface Mount Package (WG)
Order Number LM2940WG5.0/883 (5962-8958701XA)
See NS Package Number WG16A
LM2940/LM2940C
www.national.com15
Physical Dimensions inches (millimeters) unless otherwise noted (Continued)
3-Lead TO-220 Plastic Package (T)
Order Number LM2940T-5.0, LM2940T-8.0,
LM2940T-9.0, LM2940T-10, LM2940T-12, LM2940CT-5.0,
LM2940CT-12 or LM2940CT-15
NS Package Number TO3B
LM2940/LM2940C
www.national.com 16
Physical Dimensions inches (millimeters) unless otherwise noted (Continued)
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DEVICES OR SYSTEMS WITHOUT THE EXPRESS WRITTEN APPROVAL OF THE PRESIDENT AND GENERAL
COUNSEL OF NATIONAL SEMICONDUCTOR CORPORATION. As used herein:
1. Life support devices or systems are devices or
systems which, (a) are intended for surgical implant
into the body, or (b) support or sustain life, and
whose failure to perform when properly used in
accordance with instructions for use provided in the
labeling, can be reasonably expected to result in a
significant injury to the user.
2. A critical component is any component of a life
support device or system whose failure to perform
can be reasonably expected to cause the failure of
the life support device or system, or to affect its
safety or effectiveness.
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www.national.com
3-Lead TO-263 Surface Mount Package (MP)
Order Number LM2940S-5.0, LM2940S-8.0,
LM2940S-9.0, LM2940S-10, LM2940S-12,
LM2940CS-5.0, LM2940CS-12 or LM2940CS-15
NS Package Number TS3B
LM2940/LM2940C 1A Low Dropout Regulator
National does not assume any responsibility for use of any circuitry described, no circuit patent licenses are implied and National reserves the right at any time without notice to change said circuitry and specifications.
Products > Analog - Regulators > Linear Regulators - Low Dropout Voltage > Positive Voltage - Fixed > LM2940C
Generic P/N 2940C
General Description
National Semiconductor Company
Design Purchasing Quality Company Jobs
Product Folder
LM2940C 1A Low Dropout Regulator
Contents
lGeneral Description
lFeatures
lDatasheet
lPackage Availability, Models, Samples
& Pricing
Parametric Table
Multiple Output Capability No
On/Off Pin No
Error Flag No
Input Voltage, max (Volt) 26
Output Current, max 1 Amp
Dropout Voltage, typ (Volt) .50
Quiescent Current, typ (mA) 10
Output Voltage (Volt) 12,15,5,9
The LM2940/LM2940C positive voltage regulator features the ability to source 1A of output
current with a dropout voltage of typically 0.5V and a maximum of 1V over the entire
temperature range. Furthermore, a quiescent current reduction circuit has been included
which reduces the ground current when the differential between the input voltage and the
output voltage exceeds approximately 3V. The quiescent current with 1A of output current
and an input-output differential of 5V is therefore only 30 mA. Higher quiescent currents
only exist when the regulator is in the dropout mode (VIN - VOUT [Less_Than_Or_Equal]
3V).
Designed also for vehicular applications, the LM2940/LM2940C and all regulated circuitry
are protected from reverse battery installations or 2-battery jumps. During line transients,
such as load dump when the input voltage can momentarily exceed the specified maximum
Features
Datasheet
Please use Adobe Acrobat to view PDF file(s).
If you have trouble printing, see Printing Problems.
Package Availability, Models, Samples & Pricing
operating voltage, the regulator will automatically shut down to protect both the internal
circuits and the load. The LM2940/LM2940C cannot be harmed by temporary mirror-image
insertion. Familiar regulator features such as short circuit and thermal overload protection
are also provided.
lDropout voltage typically 0.5V @IO = 1A
lOutput current in excess of 1A
lOutput voltage trimmed before assembly
lReverse battery protection
lInternal short circuit current limit
lMirror image insertion protection
lP+ Product Enhancement tested
Title Size
(in Kbytes) Date View Online Download Receive via Email
LM2940/LM2940C 1A Low Dropout Regulator 409 Kbytes 21-Jul-00 View Online Download Receive via Email
Part Number Package Status Models Samples
&
Electronic
Orders
Budgetary Pricing Std
Pack
Size
Package
Marking
Type # pins SPICE IBIS Quantity $US each
LM2940CT-12 TO-220 3 Full production N/A N/A .
Order Parts
1K+ $0.6600 tube
of
45
[logo]¢U¢Z¢2¢T
LM2940CT
-12 P+
LM2940CT-15 TO-220 3 Full production N/A N/A .
Order Parts
1K+ $0.6600 tube
of
45
[logo]¢U¢Z¢2¢T
LM2940CT
-15 P+
LM2940CT-5.0 TO-220 3 Full production N/A N/A .
Order Parts
1K+ $0.6600 tube
of
45
[logo]¢U¢Z¢2¢T
LM2940CT
-5.0 P+
LM2940CT-9.0 TO-220 3 Full production N/A N/A .
Order Parts
1K+ $0.6600 tube
of
45
[logo]¢U¢Z¢2¢T
LM2940CT
-9.0 P+
LM2940CS-12 TO 263 3Full production N/A N/A Samples
Order Parts
1K+ $0.8600 tube
of
45
[logo]¢U¢Z¢2¢T
LM2940CS
-12 P+
LM2940CS-15 TO 263 3Full production N/A N/A Samples
Order Parts
1K+ $0.8600 tube
of
45
[logo]¢U¢Z¢2¢T
LM2940CS
-15 P+
LM2940CS-5.0 TO 263 3Full production N/A N/A Samples
Order Parts
1K+ $0.8600 tube
of
45
[logo]¢U¢Z¢2¢T
LM2940CS
-5.0 P+
LM2940CS-9.0 TO 263 3Full production N/A N/A Samples
Order Parts
1K+ $0.8600 tube
of
45
[logo]¢U¢Z¢2¢T
LM2940CS
-9.0 P+
LM2940CSX-12 TO 263 3Full production N/A N/A .1K+ $0.8900 reel
of
500
[logo]¢U¢Z¢2¢T
LM2940CS
-12 P+
LM2940CSX-15 TO 263 3Full production N/A N/A .1K+ $0.8900 reel
of
500
[logo]¢U¢Z¢2¢T
LM2940CS
-15 P+
LM2940CSX-5.0 TO 263 3Full production N/A N/A .
Order Parts
1K+ $0.8900 reel
of
500
[logo]¢U¢Z¢2¢T
LM2940CS
-5.0 P+
LM2940CSX-9.0 TO 263 3Full production N/A N/A .
Order Parts
1K+ $0.8900 reel
of
500
[logo]¢U¢Z¢2¢T
LM2940CS
-9.0 P+
LM2940CT-12 MDC die Full production N/A N/A . N/A -
LM2940CT-15 MDC die Full production N/A N/A . N/A -
LM2940CT-12 MWC wafer Full production N/A N/A . N/A -
LM2940CT-15 MWC wafer Full production N/A N/A . N/A -
[Information as of 2-Sep-2000]
LM2940CT-5 MWC wafer Full production N/A N/A . N/A -
LM2940-12 MW8 wafer Full production N/A N/A . N/A -
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