LM2941T/LB08 - NATIONAL SEMICONDUCTOR

LM2941,LM2941C

LM2941/LM2941C 1A Low Dropout Adjustable Regulator

Literature Number: SNVS770E

LM2941/LM2941C

June 8, 2011

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 dif-

ferential 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 there-

fore only 30mA. Higher quiescent currents only exist when the

regulator is in the dropout mode (VIN − VOUT ≤ 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

■LLP space saving package

■Output voltage adjustable from 5V to 20V

■Dropout voltage typically 0.5V @ IO = 1A

■Output current in excess of 1A

■Trimmed reference voltage

■Reverse battery protection

■Internal short circuit current limit

■Mirror image insertion protection

■P+ Product Enhancement tested

■TTL, CMOS compatible ON/OFF switch

Connection Diagram and Ordering Information

TO-220 Plastic Package

882302

Top View

Order Number LM2941T or LM2941CT

See NS Package Number TO5A

TO-263 Surface-Mount Package

882308

Order Number LM2941S, LM2941SX or LM2941CS,

LM2941CSX

See NS Package Number TS5B

8-Lead LLP Surface Mount Package

882333

Top View

Ordering Number LM2941LD, LM2941LDX

See NS Package Number LDC08A

LM2941/LM2941C 1A Low Dropout Adjustable Regulator

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 4) Internally Limited

Maximum Junction Temperature 150°C

Storage Temperature Range −65°C ≤ TJ ≤ +150°C

Soldering Temperature (Note 9)

TO-220 (T), Wave 260°C, 10s

TO-263 (S) 235°C, 30s

LLP-8 (LD) 235°C, 30s

ESD Rating (Note 2) ±2 kV

Operating Ratings

Maximum Input Voltage 26V

Temperature Range

LM2941T −40°C ≤ TJ ≤ 125°C

LM2941CT 0°C ≤ TJ ≤ 125°C

LM2941S −40°C ≤ TJ ≤ 125°C

LM2941CS 0°C ≤ TJ ≤ 125°C

LM2941LD −40°C ≤ TJ ≤ 125°C

Electrical Characteristics—LM2941T, LM2941S, LM2941LD

5V ≤ VO ≤ 20V, VIN = VO + 5V, CO = 22μF, unless otherwise specified. Specifications in standard typeface apply for TJ = 25°C,

while those in boldface type apply over the full Operating Temperature Range.

Parameter Conditions Typ

LM2941T

LM2941S

LM2941LD

Limit

Units

(Limits)

Reference Voltage 5mA ≤ IO ≤ 1A (Note 7)1.275 1.237/1.211 V(min)

1.313/1.339 V(max)

Line Regulation VO + 2V ≤ VIN ≤ 26V, IO = 5mA 4 10/10 mV/V(max)

Load Regulation 50mA ≤ IO ≤ 1A 7 10/10 mV/V(max)

Output Impedance 100 mADC and 20 mArms

fO = 120Hz 7 mΩ/V

Quiescent Current VO + 2V ≤ VIN < 26V, IO = 5mA 10 15/20 mA(max)

VIN = VO + 5V, IO = 1A 30 45/60 mA(max)

RMS Output Noise,

% of VOUT

10Hz–100kHz

IO = 5mA 0.003 %

Ripple Rejection fO = 120Hz, 1 Vrms, IL = 100mA 0.005 0.02/0.04 %/V(max)

Long Term Stability 0.4 %/1000 Hr

Dropout Voltage IO = 1A 0.5 0.8/1.0 V(max)

IO = 100mA 110 200/200 mV(max)

Short Circuit Current VIN Max = 26V (Note 8)1.9 1.6 A(min)

Maximum Line

Transient

VO Max 1V Above Nominal VO

RO = 100, t ≤ 100ms 75 60/60 V(min)

Maximum Operational

Input Voltage 31 26/26 VDC

Reverse Polarity

DC Input Voltage RO = 100, VO ≥ −0.6V −30 −15/−15 V(min)

Reverse Polarity

Transient Input Voltage t ≤ 100ms, RO = 100Ω −75 −50/−50 V(min)

ON/OFF Threshold

Voltage ON IO ≤ 1A 1.30 0.80/0.80 V(max)

ON/OFF Threshold

Voltage OFF IO ≤ 1A 1.30 2.00/2.00 V(min)

ON/OFF Threshold

Current VON/OFF = 2.0V, IO ≤ 1A 50 100/300 μA(max)

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LM2941/LM2941C

Electrical Characteristics—LM2941CT, LM2941CS

5V ≤ VO ≤ 20V, VIN = VO + 5V, CO = 22μF, unless otherwise specified. Specifications in standard typeface apply for TJ = 25°C,

while those in boldface type apply over the full Operating Temperature Range.

Parameter Conditions Typ Limit Units

(Note 6)(Limits)

Reference Voltage 5mA ≤ IO ≤ 1A (Note 7)1.275 1.237/1.211 V(min)

1.313/1.339 V(max)

Line Regulation VO + 2V ≤ VIN ≤ 26V, IO = 5mA 4 10 mV/V(max)

Load Regulation 50mA ≤ IO ≤ 1A 7 10 mV/V(max)

Output Impedance 100 mADC and 20 mArms

fO = 120Hz 7 mΩ/V

Quiescent Current VO + 2V ≤ VIN < 26V, IO = 5mA 10 15 mA(max)

VIN = VO + 5V, IO = 1A 30 45/60 mA(max)

RMS Output Noise,

% of VOUT

10Hz–100kHz

IO = 5mA 0.003 %

Ripple Rejection fO = 120Hz, 1 Vrms, IL = 100mA 0.005 0.02 %/V(max)

Long Term Stability 0.4 %/1000 Hr

Dropout Voltage IO = 1A 0.5 0.8/1.0 V(max)

IO = 100mA 110 200/200 mV(max)

Short Circuit Current VIN Max = 26V (Note 8)1.9 1.6 A(min)

Maximum Line

Transient

VO Max 1V Above Nominal VO

RO = 100Ω, T ≤ 100ms 55 45 V(min)

Maximum Operational

Input Voltage 31 26 VDC

Reverse Polarity

DC Input Voltage RO = 100Ω, VO ≥ −0.6V −30 −15 V(min)

Reverse Polarity

Transient Input Voltage T ≤ 100ms, RO = 100Ω −55 −45 V(min)

ON/OFF Threshold

Voltage ON IO ≤ 1A 1.30 0.80 V(max)

ON/OFF Threshold

Voltage OFF IO ≤ 1A 1.30 2.00 V(min)

ON/OFF Threshold

Current VON/OFF = 2.0V, IO ≤ 1A 50 100 μA(max)

Thermal Performance

Thermal Resistance

Junction-to-Case, θJC

5-Lead TO-220 3 °C/W

5-Lead TO-263 3 °C/W

8–Lead LLP 5.3 °C/W

Thermal Resistance

Junction-to-Ambient, θJA

(Note 4)

5-Lead TO-220 53 °C/W

5-Lead TO-263 73 °C/W

8-Lead LLP 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: The Human Body Model (HBM) is a 100 pF capacitor discharged through a 1.5kΩ resistor into each pin. Test method is per JESD22–A114.

Note 3: 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 4: 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

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LM2941/LM2941C

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 5: 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 6: 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 7: The output voltage range is 5V to 20V and is determined by the two external resistors, R1 and R2. See Typical Application Circuit.

Note 8: Output current capability will decrease with increasing temperature, but will not go below 1A at the maximum specified temperatures.

Note 9: Refer to JEDEC J-STD-020C for surface mount device (SMD) package reflow profiles and conditions. Unless otherwise stated, the temperature and time

are for Sn-Pb (STD) only.

Typical Performance Characteristics

Dropout Voltage

882311

Dropout Voltage vs. Temperature

882312

Output Voltage

882313

Quiescent Current vs. Temperature

882314

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LM2941/LM2941C

Quiescent Current

882315

Quiescent Current

882316

Line Transient Response

882317

Load Transient Response

882318

Ripple Rejection

882319

Output Impedance

882320

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LM2941/LM2941C

Low Voltage Behavior

882321

Low Voltage Behavior

882322

Output Capacitor ESR

882323

Output at Voltage Extremes

882324

Output at Voltage Extremes

882325

Peak Output Current

882326

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LM2941/LM2941C

Maximum Power Dissipation (TO-220)

882327

Maximum Power Dissipation (TO-3)

882328

Maximum Power Dissipation (TO-263) (Note 4)

882329

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

100mV from the nominal value obtained at (VOUT + 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 condi-

tions of low dissipation or by using pulse techniques such that

the average chip temperature is not significantly affected.

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 spec-

ified frequency range.

Quiescent Current: That part of the positive input current

that does not contribute to the positive load current. The reg-

ulator 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 VO: The percentage change in

output voltage for a thermal variation from room temperature

to either temperature extreme.

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LM2941/LM2941C

Application Hints

LLP MOUNTING

The LDC08A (Pullback) 8-Lead LLP package requires spe-

cific mounting techniques which are detailed in National

Semiconductor Application Note # 1187. Referring to the sec-

tion PCB Design Recommendations in AN-1187 (Page 5),

it should be noted that the pad style which should be used

with the LLP package is the NSMD (non-solder mask defined)

type.

The DAP (exposed pad) on the bottom of the LLP package is

internally connected to device ground at pin 2 and pin 7. The

DAP can be connected directly to ground, or the DAP may be

left floating (i.e. no direct electrical connection). The DAP

must not be connected to any potential other than ground.

For the LM2941LD in the LDC08A 8-Lead LLP package, the

junction-to-case thermal rating, θJC, is 5.3° C/W, where the

case is the bottom of the package at the center of the DAP.

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LM2941/LM2941C

Typical Applications

5V to 20V Adjustable Regulator

882303

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.

** COUT must be at least 22μF 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

882306

*** To assure shutdown, select Resistor R3 to guarantee at least 300μA of pull-up current when S1 is open. (Assume 2V at the ON/OFF pin.)

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LM2941/LM2941C

Equivalent Schematic Diagram

882301

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LM2941/LM2941C

Physical Dimensions inches (millimeters) unless otherwise noted

Order Number LM2941T or LM2941CT

NS Package Number T05A

TO-263 5-Lead Plastic Surface Mount Package

Order Number LM2941S, LM2941SX, LM2941CS or LM2941CSX

NS Package Number TS5B

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LM2941/LM2941C

8-Lead LLP Surface Mount Package

Order Number LM2941LD, LM2941LDX

NS Package Number LDC08A

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LM2941/LM2941C

Notes

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LM2941/LM2941C

Notes

LM2941/LM2941C 1A Low Dropout Adjustable Regulator

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