LM2941x 1-A Low Dropout Adjustable Regulator
- SNVS770I June 1999 – January 2015 LM2941 , LM2941C
  
  PRODUCTION DATA.

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DATA SHEET

LM2941x 1-A Low Dropout Adjustable Regulator

1 Features

Operating V_IN Range: 6 V to 26 V
Output Voltage Adjustable From 5 V to 20 V
Dropout Voltage Typically 0.5 V at I_OUT = 1 A
Output Current in Excess of 1 A
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
WSON Space-Saving Package

2 Applications

Industrial
Automotive

3 Description

The LM2941 positive voltage regulator features the ability to source 1 A of output current with a typical dropout voltage of 0.5 V and a maximum of 1 V 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 3 V. The quiescent current with 1 A of output current and an input-output differential of 5 V is therefore only 30 mA. Higher quiescent currents only exist when the regulator is in the dropout mode (V_IN − V_OUT ≤ 3 V).

Designed also for vehicular applications, the LM2941 and all regulated circuitry are protected from reverse battery installations 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.

Device Information⁽¹⁾

PART NUMBER	PACKAGE	BODY SIZE (NOM)
LM2941	WSON (8)	4.00 mm x 4.00 mm
	TO-263 (5)	10.16 mm x 8.42 mm
	TO-220 (5)	14.986 mm x 10.16 mm
	TO-220 (5)	10.16 mm x 8.51 mm
LM2941C	TO-263 (5)	10.16 mm x 8.42 mm
	TO-220 (5)	14.986 mm x 10.16 mm
	TO-220 (5)	10.16 mm x 8.51 mm

For all available packages, see the orderable addendum at the end of the datasheet.

Simplified Schematic

4 Revision History

Changes from H Revision (December 2014) to I Revision

Changed update pin names to TI nomenclature Go

Changes from G Revision (April 2013) to H Revision

Added Device Information and ESD Ratings tables, Feature Description section, Device Functional Modes, Application and Implementation section, Power Supply Recommendations section, Layout section, Device and Documentation Support section, and Mechanical, Packaging, and Orderable Information section; updated Thermal InfoGo

Changes from F Revision (April 2013) to G Revision

Changed layout of National Data Sheet to TI formatGo

5 Pin Configuration and Functions

TO-220 (KC) Plastic Package

4 Pins

Top View

TO-263 (KTT) Surface-Mount Package

4 Pins

WSON (NGN)Surface Mount Package

8 Leads

Top View

Pin Functions

PIN				TYPE	DESCRIPTION
NAME	KC	KTT	NGN	TYPE	DESCRIPTION
ADJ	1	1	8	I	Sets output voltage
ON/OFF	2	2	1	I	Enable/Disable control
GND	3	3	2, 7	—	Ground
IN	4	4	3	I	Input supply
OUT	5	5	5	O	Regulated output voltage. This pin requires an output capacitor to maintain stability. See the Detailed Design Procedure section for output capacitor details.
NC	—	—	4, 6	—	No internal connection. Connect to GND or leave open.

6 Specifications

6.1 Absolute Maximum Ratings⁽¹⁾⁽²⁾

		MIN	MAX	UNIT
Input voltage (Survival Voltage, ≤ 100 ms)	LM2941T, LM2941S, LM2941LD		60	V
Input voltage (Survival Voltage, ≤ 100 ms)	LM2941CT, LM2941CS		45	V
Internal power dissipation ⁽³⁾		Internally Limited
Maximum junction temperature			150	°C
Soldering remperature⁽⁴⁾	TO-220 (T), Wave, 10 s		260	°C
	TO-263 (S), 30 s		235	°C
	WSON-8 (LD), 30 s		235	°C
Storage temperature, T_stg		−65	150	°C

(1) Stresses beyond those listed under Absolute Maximum Ratings may cause permanent damage to the device. These are stress ratings only, which do not imply functional operation of the device at these or any other conditions beyond those indicated under Recommended Operating Conditions. Exposure to absolute-maximum-rated conditions for extended periods may affect device reliability.

(2) If Military/Aerospace specified devices are required, please contact the Texas Instruments Sales Office/Distributors for availability and specifications.

(3) The maximum power dissipation is a function of T_J(max), R_θJA, and T_A. The maximum allowable power dissipation at any ambient temperature is P_D = (T_J(max) − T_A)/R_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 PC board copper area thermally connected to the package. The value R_θJA for the WSON 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 WSON package, refer to Application Note AN-1187 (SNOA401). It is recommended that 6 vias be placed under the center pad to improve thermal performance.

(4) 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.

6.2 ESD Ratings

			VALUE	UNIT
V_(ESD)	Electrostatic discharge	Human-body model (HBM), per ANSI/ESDA/JEDEC JS-001⁽¹⁾	±2000	V

(1) JEDEC document JEP155 states that 500-V HBM allows safe manufacturing with a standard ESD control process.

6.3 Recommended Operating Conditions

		MIN	MAX	UNIT
Temperatures	LM2941T	−40	125	°C
	LM2941CT	0	125
	LM2941S	−40	125
	LM2941CS	0	125
	LM2941LD	−40	125

6.4 Thermal Information

THERMAL METRIC⁽¹⁾⁽³⁾		LM2941LD	LM2941S, LM2941T		UNIT
		WSON (NGN)	TO-263 (KTT)	TO-220 (KC)
		8 PINS	5 PINS	5 PINS
R_θJA	Junction-to-ambient thermal resistance	40.5	41	32.1	°C/W
R_θJC(top)	Junction-to-case (top) thermal resistance	26.2	43.2	25.6
R_θJB	Junction-to-board thermal resistance	17	22.9	18.3
ψ_JT	Junction-to-top characterization parameter	0.2	11.4	8.5
ψ_JB	Junction-to-board characterization parameter	17.2	21.9	17.7
R_θJC(bot)	Junction-to-case (bottom) thermal resistance	3.2	0.9	0.7

(1) For more information about traditional and new thermal metrics, see the IC Package Thermal Metrics application report, SPRA953.

6.5 Electrical Characteristics: LM2941T, LM2941S, LM2941LD

5 V ≤ V_OUT ≤ 20 V, V_IN = V_OUT + 5 V, C_OUT = 22 μF, unless otherwise specified. MIN (minimum) and MAX (maximum) specifications in apply over the full Operating Temperature Range (unless otherwise specified) and typical values apply at T_J = 25°C.

PARAMETER	TEST CONDITIONS	MIN	TYP	MAX	UNIT
Reference voltage	5 mA ≤ I_OUT ≤ 1 A⁽¹⁾	1.211	1.275	1.339	V
Reference voltage	5 mA ≤ I_OUT ≤ 1 A⁽¹⁾, T_J = 25°C	1.237	1.275	1.313	V
Line regulation	V_OUT + 2 V ≤ V_IN ≤ 26 V, I_OUT = 5 mA		4	10	mV/V
Load regulation	50 mA ≤ I_OUT ≤ 1 A		7	10	mV/V
Output impedance	100 mADC and 20 mArms, ƒ_OUT = 120 Hz		7		mΩ/V
Quiescent current	V_OUT + 2 V ≤ V_IN < 26 V, I_OUT = 5 mA		10	20	mA
	V_OUT + 2 V ≤ V_IN < 26 V, I_OUT = 5 mA, T_J = 25°C		10	15	mA
	V_IN = V_OUT + 5 V, I_OUT = 1 A		30	60	mA
	V_IN = V_OUT + 5 V, I_OUT = 1 A, T_J = 25°C		30	45	mA
RMS output noise, % of V_OUT	10 Hz to 100 kHz, I_OUT = 5 mA		0.003%
Ripple rejection	ƒ_OUT = 120 Hz, 1 Vrms, I_L = 100 mA		0.005	0.04	%/V
Ripple rejection	ƒ_OUT = 120 Hz, 1 Vrms, I_L = 100 mA, T_J = 25°C		0.005	0.02	%/V
Long-term stability			0.4		%/1000 Hr
Dropout voltage	I_OUT = 1 A		0.5	1	V
	I_OUT = 1 A, T_J = 25°C		0.5	0.8	V
	I_OUT = 100 mA		110	200	mV
Short-circuit current	V_IN max = 26 V⁽²⁾	1.6	1.9		A
Maximum line transient	V_OUT max 1 V above nominal V_OUT R_OUT = 100 Ω, t ≤ 100 ms	60	75		V
Maximum operational input voltage		26	31		V_DC
Reverse polarity DC input voltage	R_OUT = 100 Ω, V_OUT ≥ −0.6 V	−15	−30		V
Reverse polarity transient input voltage	t ≤ 100 ms, R_OUT = 100 Ω	−50	−75		V
ON/OFF threshold voltage ON	I_OUT ≤ 1 A		1.30	0.80	V
ON/OFF threshold voltage OFF	I_OUT ≤ 1 A	2	1.3		V
ON/OFF threshold current	V_ON/OFF = 2 V, I_OUT ≤ 1 A		50	300	μA
ON/OFF threshold current	V_ON/OFF = 2 V, I_OUT ≤ 1 A, T_J = 25°C		50	100	μA

(1) The output voltage range is 5 V to 20 V and is determined by the two external resistors, R1 and R2. See Figure 18.

(2) Output current capability will decrease with increasing temperature, but will not go below 1 A at the maximum specified temperatures.

6.6 Electrical Characteristics: LM2941CT, LM2941CS

PARAMETER	TEST CONDITIONS	MIN	TYP	MAX	UNIT
Reference voltage	5 mA ≤ I_OUT ≤ 1 A⁽¹⁾	1.211	1.275	1.339	V
Reference voltage	5 mA ≤ I_OUT ≤ 1 A⁽¹⁾, T_J = 25°C	1.237	1.275	1.313	V
Line regulation	V_OUT + 2 V ≤ V_IN ≤ 26 V, I_OUT = 5 mA, T_J = 25°C		4	10	mV/V
Load regulation	50 mA ≤ I_OUT ≤ 1 A, T_J = 25°C		7	10	mV/V
Output impedance	100 mADC and 20 mArms, ƒ_OUT = 120 Hz		7		mΩ/V
Quiescent current	V_OUT + 2 V ≤ V_IN < 26 V, I_OUT = 5 mA, T_J = 25°C		10	15	mA
	V_IN = V_OUT + 5 V, I_OUT = 1 A		30	60	mA
	V_IN = V_OUT + 5 V, I_OUT = 1 A, T_J = 25°C		30	45	mA
RMS output noise, % of V_OUT	10 Hz to 100 kHz I_OUT = 5 mA		0.003%
Ripple rejection	ƒ_OUT = 120Hz, 1 Vrms, I_L = 100 mA, T_J = 25°C		0.005	0.02	%/V
Long-term stability			0.4		%/1000 Hr
Dropout voltage	I_OUT = 1A		0.5	1	V
	I_OUT = 1A, T_J = 25°C		0.5	0.8	V
	I_OUT = 100 mA		110	200	mV
Short-circuit current	V_IN max = 26 V⁽²⁾, T_J = 25°C	1.6	1.9		A
Maximum line transient	V_OUT max 1 V above nominal V_OUT, R_OUT = 100 Ω, t ≤ 100 ms, , T_J = 25°C	45	55		V
Maximum operational input voltage	T_J = 25°C	26	31		V_DC
Reverse polarity DC input voltage	R_OUT = 100 Ω, V_OUT ≥ −0.6 V, T_J = 25°C	−15	−30		V
Reverse polarity transient input voltage	t ≤ 100 ms, R_OUT = 100 Ω, T_J = 25°C	−45	−55		V
ON/OFF threshold voltage ON	I_OUT ≤ 1 A, T_J = 25°C		1.3	0.8	V
ON/OFF threshold voltage OFF	I_OUT ≤ 1 A, T_J = 25°C	2	1.3		V
ON/OFF threshold current	V_ON/OFF = 2 V, I_OUT ≤ 1 A, T_J = 25°C		50	100	μA

(1) The output voltage range is 5 V to 20 V and is determined by the two external resistors, R1 and R2. See Typical Application.

(2) Output current capability will decrease with increasing temperature, but will not go below 1 A at the maximum specified temperatures.

6.7 Typical Characteristics

Figure 1. Dropout Voltage

Figure 3. Output Voltage

Figure 5. Quiescent Current

Figure 7. Line Transient Response

Figure 9. Ripple Rejection

Figure 11. Low Voltage Behavior

Figure 13. Output Capacitor ESR

Figure 15. Output at Voltage Extremes

Figure 17. Maximum Power Dissipation (TO-220)

Figure 2. Dropout Voltage vs. Temperature

Figure 4. Quiescent Current vs. Temperature

Figure 6. Quiescent Current

Figure 8. Load Transient Response

Figure 10. Output Impedance

Figure 12. Low Voltage Behavior

Figure 14. Output at Voltage Extremes

Figure 16. Peak Output Current

7 Detailed Description

7.1 Overview

The LM2941 positive voltage regulator features the ability to source 1 A of output current with a dropout voltage of typically 0.5 V and a maximum of 1 V 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 3 V. The quiescent current with 1 A of output current and an input-output differential of 5 V is therefore only 30 mA. Higher quiescent currents only exist when the regulator is in the dropout mode (V_IN – V_OUT ≤ 3 V).

7.2 Functional Block Diagram

7.3 Feature Description

7.3.1 Short-Circuit Current Limit

The internal current limit circuit is used to protect the LDO against high-load current faults or shorting events. The LDO is not designed to operate in a steady-state current limit. During a current-limit event, the LDO sources constant current. Therefore, the output voltage falls when load impedance decreases. Note also that if a current limit occurs and the resulting output voltage is low, excessive power may be dissipated across the LDO, resulting a thermal shutdown of the output.

7.3.2 Overvoltage Shutdown (OVSD)

Input voltage greater than typically 30 V will cause the LM2941 output to be disabled. When operating with the input voltage greater than the maximum recommended input voltage of 26 V, the device performance is not ensured. Continuous operation with the input voltage greater than the maximum recommended input voltage is discouraged.

7.3.3 Thermal Shutdown (TSD)

The LM2941 contains the thermal shutdown circuitry to turn off the output when excessive heat is dissipated in the LDO. The internal protection circuitry of the LM2941 is designed to protect against thermal overload conditions. The TSD circuitry is not intended to replace proper heat sinking. Continuously running the device into thermal shutdown degrades its reliability as the junction temperature will be exceeding the absolute maximum junction temperature rating.

7.3.4 Thermal Overload Protection

The LM2941 incorporates a linear form of thermal protection that limits the junction temperature (T_J) to typically 155°C.

Should the LM2941 see a fault condition that results in excessive power dissipation and the junction temperature approaches 155°C, the device will respond by reducing the output current (which reduces the power dissipation) to hold the junction temperature at 155°C.

Thermal Overload protection is not an ensured operating condition. Operating at, or near to, the thermal overload condition for any extended period of time is not encouraged, or recommended, as this may shorten the lifetime of the device.

7.4 Device Functional Modes

7.4.1 Operation With ON/OFF Control

The ON/OFF pin has no internal pull-up or pull-down to establish a default condition and, as a result, this pin must be terminated externally, either actively or passively. The ON/OFF pin requires a low level to enable the output, and a high level to disable the output. To ensure reliable operation, the ON/OFF pin voltage must rise above the maximum ON/OFF(OFF) voltage threshold (2 V) to disable the output, and must fall below the minimum ON/OFF(ON) voltage threshold (0.8 V) to enable the output. If the ON/OFF function is not needed this pin can be connected directly to Ground. If the ON/OFF pin is being pulled to a high state through a series resistor, an allowance must be made for the ON/OFF pin current that will cause a voltage drop across the pull-up resistor

8 Application and Implementation

NOTE

Information in the following applications sections is not part of the TI component specification, and TI does not warrant its accuracy or completeness. TI’s customers are responsible for determining suitability of components for their purposes. Customers should validate and test their design implementation to confirm system functionality.

8.1 Application Information

Figure 18 shows the typical application circuit for the LM2941. The output capacitor, C_OUT, must have a capacitance value of at least 22 µF with an equivalent series resistance (ESR) of at least 100 mΩ, but no more than 1 Ω. The minimum capacitance value and the ESR requirements apply across the entire expected operating ambient temperature range.

8.2 Typical Application

Note: Using 1 kΩ for R1 will ensure that the bias current error from 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.

Figure 18. 5-V to 20-V Adjustable Regulator

8.2.1 Design Requirements

DESIGN PARAMETER	EXAMPLE VALUE
Input voltage range	10 V to 26 V
Output voltage	15 V
Output current range	5 mA to 1 A
Input capacitor value	0.47 µF
Output capacitor value	22 µF minimum
Output capacitor ESR range	100 mΩ to 1 Ω

8.2.2 Detailed Design Procedure

8.2.2.1 Output Capacitor

A tantalum capacitor with a minimum capacitance value of 22 μF, and ESR in the range of 0.01 Ω to 5 Ω, is required at the output pin for loop stability. It must be located less than 1 cm from the device. There is no limitation on any additional capacitance.

Alternately, a high quality X5R/X7R 22 μF ceramic capacitor may be used for the output capacitor only if an appropriate value of series resistance is added to simulate the ESR requirement. The ceramic capacitor selection must include an appropriate voltage de-rating of the capacitance value due to the applied output voltage. The series resistor (for ESR simulation) should be in the range of 0.1 Ω to 1 Ω.

8.2.2.2 Setting the Output Voltage

The output voltage range is 5 V to 20 V and is set by the two external resistors, R1 and R2. See the Figure 18. The output voltage is given by the formula:

Equation 1. V_OUT = V_REF × ((R1 + R2) / R1)

where

V_REF is typically 1.275 V

Using 1 kΩ for R1 will ensure that the bias current error of the adjust pin will be negligible. Using a R1 value higher than 10 kΩ may cause the output voltage to shift across temperature due to variations in the adjust pin bias current.

Calculating the upper resistor (R2) value of the pair when the lower resistor (R1) value is known is accomplished with the following formula:

Equation 2. R2 = R1 × ((V_OUT / V_REF) – 1)

The resistors used for R1 and R2 should be high quality, tight tolerance, and with matching temperature coefficients. It is important to remember that, although the value of V_REF is ensured, the final value of V_OUT is not. The use of low quality resistors for R1 and R2 can easily produce a V_OUT value that is unacceptable.

8.2.3 Application Curves

Figure 19. Low Voltage Behavior

Figure 20. Output at Voltage Extremes