LM2941/LM2941C
1A Low Dropout Adjustable Regulator
General Description
The LM2941 positive voltage regulator features the ability to
source 1A of output current with a typical dropout voltage of
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 pin 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 (V
IN
−
V
OUT
≤3V).
Designed also for vehicular applications, the LM2941 and all
regulated circuitry are protected from reverse battery instal-
lations or two-battery jumps. During line transients, such as
load dump when the input voltage can momentarily exceed
the specified maximum operating voltage, the regulator will
automatically shut down to protect both the internal circuits
and the load. Familiar regulator features such as short circuit
and thermal overload protection are also provided.
Features
nLLP space saving package
nOutput voltage adjustable from 5V to 20V
nDropout voltage typically 0.5V @I
O
=1A
nOutput current in excess of 1A
nTrimmed reference voltage
nReverse battery protection
nInternal short circuit current limit
nMirror image insertion protection
nP
+
Product Enhancement tested
nTTL, CMOS compatible ON/OFF switch
Connection Diagram and Ordering Information
TO-220 Plastic Package TO-263 Surface-Mount Package
00882302
Tep View
Order Number LM2941T or
LM2941CT
See NS Package Number TO5A
00882308
Order Number LM2941S, LM2941SX
or LM2941CS, LM2941CSX
See NS Package Number TS5B
00882309
16-Lead Ceramic Dual-in-Line
Package
16-Lead Ceramic Surface Mount
Package
8-Lead LLP Surface Mount
Package
00882331
Top View
Order Number LM2941J/883
LM2941J-QMLV, 5962-9166701QEA
See NS Package Number J16A
00882332
Top View
Order Number LM2941WG/883
LM2941WG-QMLV,
5962-9166701QYA
See NS Package Number WG16A
00882333
Top View
Ordering Number LM2941LD,
LM2941LDX
See NS Package Number LDC08A
August 2002
LM2941/LM2941C 1A Low Dropout Adjustable Regulator
© 2002 National Semiconductor Corporation DS008823 www.national.com
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 (Survival Voltage, ≤100ms)
LM2941T, LM2941S, LM2941LD 60V
LM2941CT, LM2941CS 45V
Internal Power Dissipation (Note 3) Internally Limited
Maximum Junction Temperature 150˚C
Storage Temperature Range −65˚C ≤T
J
≤+150˚C
Lead Temperature
(Soldering, 10 seconds)
TO-220 (T) Package 260˚C
TO-263 (S) Package 260˚C
ESD susceptibility to be determined.
Operating Ratings
Maximum Input Voltage 26V
Temperature Range
LM2941T −40˚C ≤T
J
≤125˚C
LM2941CT 0˚C ≤T
J
≤125˚C
LM2941S −40˚C ≤T
J
≤125˚C
LM2941CS 0˚C ≤T
J
≤125˚C
LM2941J −55˚C ≤T
J
≤125˚C
LM2941WG −55˚C ≤T
J
≤125˚C
LM2941LD −40˚C ≤T
J
≤125˚C
Electrical Characteristics—LM2941T, LM2941S, LM2941J, LM2941WG,
LM2941LD
5V ≤V
O
≤20V, V
IN
=V
O
+ 5V, C
O
= 22µF, unless otherwise specified. Specifications in standard typeface apply for T
J
=
25˚C, while those in boldface type apply over the full Operating Temperature Range.
Parameter Conditions Typ
LM2941J
LM2941WG
Limit
(Note 2) (Note 4)
LM2941T
LM2941S
LM2941LD
Limit
(Note 5)
Units
(Limits)
Reference Voltage 5mA ≤I
O
≤1A (Note 6) 1.275 1.237/1.211 1.237/1.211 V(min)
1.313/1.339 1.313/1.339 V(max)
Line Regulation V
O
+2V≤V
IN
≤26V, I
O
= 5mA 4 10/10 10/10 mV/V(max)
Load Regulation 50mA ≤I
O
≤1A 7 10/10 10/10 mV/V(max)
Output Impedance 100 mADC and 20 mArms 7 mΩ/V
f
O
= 120Hz
Quiescent Current V
O
+2V≤V
IN
<26V, I
O
= 5mA 10 15/20 15/20 mA(max)
V
IN
=V
O
+ 5V, I
O
= 1A 30 45/60 45/60 mA(max)
RMS Output Noise, 10Hz–100kHz 0.003 %
%ofV
OUT
I
O
= 5mA
Ripple Rejection f
O
= 120Hz, 1 Vrms, I
L
= 100mA 0.005 0.02/0.04 0.02/0.04 %/V(max)
Long Term Stability 0.4 %/1000 Hr
Dropout Voltage I
O
= 1A 0.5 0.8/1.0 0.8/1.0 V(max)
I
O
= 100mA 110 200/200 200/200 mV(max)
Short Circuit Current V
IN
Max = 26V (Note 7) 1.9 1.6/1.3 1.6 A(min)
Maximum Line V
O
Max 1V Above Nominal V
O
75 60/60 60/60 V(min)
Transient R
O
= 100, T ≤100ms
Maximum Operational
Input Voltage 31 26/26 26/26 V
DC
Reverse Polarity DC
Input Voltage
R
O
= 100, V
O
≥−0.6V −30 −15/−15 −15/−15 V(min)
Reverse Polarity
Transient Input Voltage
T≤100ms, R
O
= 100Ω−75 −50/−50 −50/−50 V(min)
ON/OFF Threshold
Voltage ON
I
O
≤1A 1.30 0.80/0.80 0.80/0.80 V(max)
ON/OFF Threshold
Voltage OFF
I
O
≤1A 1.30 2.00/2.00 2.00/2.00 V(min)
ON/OFF Threshold
Current
V
ON/OFF
= 2.0V, I
O
≤1A 50 100/300 100/300 µA(max)
LM2941/LM2941C
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Electrical Characteristics—LM2941CT, LM2941CS
5V ≤V
O
≤20V, V
IN
=V
O
+ 5V, C
O
= 22µF, unless otherwise specified. Specifications in standard typeface apply for T
J
=
25˚C, while those in boldface type apply over the full Operating Temperature Range.
Parameter Conditions Typ Limit Units
(Note 5) (Limits)
Reference Voltage 5mA ≤I
O
≤1A (Note 6) 1.275 1.237/1.211 V(min)
1.313/1.339 V(max)
Line Regulation V
O
+2V≤V
IN
≤26V, I
O
= 5mA 4 10 mV/V(max)
Load Regulation 50mA ≤I
O
≤1A 7 10 mV/V(max)
Output Impedance 100 mADC and 20 mArms 7 mΩ/V
f
O
= 120Hz
Quiescent Current V
O
+2V≤V
IN
<26V, I
O
= 5mA 10 15 mA(max)
V
IN
=V
O
+ 5V, I
O
= 1A 30 45/60 mA(max)
RMS Output Noise, 10Hz–100kHz 0.003 %
%ofV
OUT
I
O
= 5mA
Ripple Rejection f
O
= 120Hz, 1 Vrms, I
L
= 100mA 0.005 0.02 %/V(max)
Long Term Stability 0.4 %/1000 Hr
Dropout Voltage I
O
= 1A 0.5 0.8/1.0 V(max)
I
O
= 100mA 110 200/200 mV(max)
Short Circuit Current V
IN
Max = 26V (Note 7) 1.9 1.6 A(min)
Maximum Line V
O
Max 1V Above Nominal V
O
55 45 V(min)
Transient R
O
= 100Ω,T≤100ms
Maximum Operational Input
Voltage 31 26 V
DC
Reverse Polarity DC Input
Voltage
R
O
= 100Ω,V
O
≥−0.6V −30 −15 V(min)
Reverse Polarity Transient
Input Voltage
T≤100ms, R
O
= 100Ω−55 −45 V(min)
ON/OFF Threshold Voltage
ON
I
O
≤1A 1.30 0.80 V(max)
ON/OFF Threshold Voltage
OFF
I
O
≤1A 1.30 2.00 V(min)
ON/OFF Threshold Current V
ON/OFF
= 2.0V, I
O
≤1A 50 100 µA(max)
Thermal Performance
Thermal Resistance
Junction-to-Case
5-Lead TO-220 3 ˚C/W
5-Lead TO-263 3 ˚C/W
Thermal Resistance
Junction-to-Ambient
5-Lead TO-220 53 ˚C/W
5-Lead TO-263 73 ˚C/W
8-Lead LLP (Note 3) 35 ˚C/W
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 device parameter specifications may not be guaranteed under these conditions. For guaranteed specifications and test conditions, see
the Electrical Characteristics.
Note 2: A military RETS specification available upon request. For more information about military-aerospace products, see the Mil-Aero web page at
http://www.national.com/appinfo/milaero/index.html.
Note 3: The maximum power dissipation is a function of TJ(max), θJA, and TA. The maximum allowable power dissipation at any ambient temperature is PD=
(TJ(max) − TA)/θJA. If this dissipation is exceeded, the die temperature will rise above 150˚C and the LM2941 will go into thermal shutdown. If the TO-263 package
is used, the thermal resistance can be reduced by increasing the P.C. board copper area thermally connected to the package: Using 0.5 square inches of copper
area, θJA is 50˚C/W; with 1 square inch of copper area, θJA is 37˚C/W; and with 1.6 or more square inches of copper area, θJA is 32˚C/W. Thermal performance for
the LLP package was obtained using a JESD51-7 board with six vias, using no airflow and an ambient temperature of 22˚C. The value θJA for the LLP package is
specifically dependent on PCB trace area, trace material, and the number of layers and thermal vias. For improved thermal resistance and power dissipation for the
LLP package, refer to Application Note AN-1187. It is recommended that 6 vias be placed under the center pad to improve thermal performance.
Note 4: All limits guaranteed at room temperature (standard typeface) and at temperature extremes (boldface type). All limits are used to calculate Outgoing Quality
Level, and are 100% production tested.
Note 5: All limits guaranteed at room temperature (standard typeface) and at temperature extremes (boldface type). All room temperature limits are 100%
production tested. All limits at temperature extremes are guaranteed via correlation using standard Statistical Quality Control (SQC) methods.
Note 6: The output voltage range is 5V to 20V and is determined by the two external resistors, R1 and R2. See Typical Application Circuit.
LM2941/LM2941C
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Thermal Performance (Continued)
Note 7: Output current capability will decrease with increasing temperature, but will not go below 1A at the maximum specified temperatures.
Typical Performance Characteristics
Dropout Voltage Dropout Voltage vs. Temperature
00882311 00882312
Output Voltage Quiescent Current vs. Temperature
00882313 00882314
Quiescent Current Quiescent Current
00882315 00882316
LM2941/LM2941C
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Typical Performance Characteristics (Continued)
Line Transient Response Load Transient Response
00882317 00882318
Ripple Rejection Output Impedance
00882319 00882320
Low Voltage Behavior Low Voltage Behavior
00882321 00882322
LM2941/LM2941C
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Typical Performance Characteristics (Continued)
Output Capacitor ESR Output at Voltage Extremes
00882323 00882324
Output at Voltage Extremes Peak Output Current
00882325 00882326
Maximum Power Dissipation (TO-220) Maximum Power Dissipation (TO-3)
00882327 00882328
LM2941/LM2941C
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Typical Performance Characteristics (Continued)
Maximum Power Dissipation (TO-263) (Note 3)
00882329
Definition of Terms
Dropout Voltage: The input-voltage differential at which the
circuit ceases to regulate against further reduction in input
voltage. Measured when the output voltage has dropped
100 mV from the nominal value obtained at (V
OUT
+ 5V)
input, dropout voltage is dependent upon load current and
junction temperature.
Input Voltage: The DC voltage applied to the input terminals
with respect to ground.
Input-Output Differential: The voltage difference between
the unregulated input voltage and the regulated output volt-
age for which the regulator will operate.
Line Regulation: The change in output voltage for a change
in the input voltage. The measurement is made under con-
ditions of low dissipation or by using pulse techniques such
that the average chip temperature is not significantly af-
fected.
Load Regulation: The change in output voltage for a
change in load current at constant chip temperature.
Long Term Stability: Output voltage stability under accel-
erated life-test conditions after 1000 hours with maximum
rated voltage and junction temperature.
Output Noise Voltage: The rms AC voltage at the output,
with constant load and no input ripple, measured over a
specified frequency range.
Quiescent Current: That part of the positive input current
that does not contribute to the positive load current. The
regulator ground lead current.
Ripple Rejection: The ratio of the peak-to-peak input ripple
voltage to the peak-to-peak output ripple voltage.
Temperature Stability of V
O
:The percentage change in
output voltage for a thermal variation from room temperature
to either temperature extreme.
LM2941/LM2941C
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Typical Applications
5V to 20V Adjustable Regulator
00882303
Note: Using 1k for R1 will ensure that the input bias current error of the adjust pin will be negligible. Do not bypass R1 or R2. This will lead to instabilities.
* Required if regulator is located far from power supply filter.
**C
OUT 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.
1A Switch
00882306
*** To assure shutdown, select Resistor R3 to guarantee at least 300 µA of pull-up current when S1 is open. (Assume 2V at the ON/OFF pin.)
LM2941/LM2941C
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Equivalent Schematic Diagram
00882301
LM2941/LM2941C
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Physical Dimensions inches (millimeters)
unless otherwise noted
Order Number LM2941J/883
LM2941J-QMLV, 5962-9166701QEA
NS Package Number J16A
Order Number LM2941WG/883
LM2941WG-QMLV, 5962-9166701QYA
NS Package Number WG16A
LM2941/LM2941C
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Physical Dimensions inches (millimeters) unless otherwise noted (Continued)
Order Number LM2941T or LM2941CT
NS Package Number T05A
LM2941/LM2941C
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Physical Dimensions inches (millimeters) unless otherwise noted (Continued)
TO-263 5-Lead Plastic Surface Mount Package
Order Number LM2941S, LM2941SX, LM2941CS or LM2941CSX
NS Package Number TS5B
LM2941/LM2941C
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Physical Dimensions inches (millimeters) unless otherwise noted (Continued)
8-Lead LLP Surface Mount Package
Order Number LM2941LD, LM2941LDX
NS Package Number LDC08A
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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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LM2941/LM2941C 1A Low Dropout Adjustable 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.
