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Bay Linear
Inspire the Linear Power
1.25A High Current Low Dropout
Voltage Regulator Adjustable
LM2940/2941
Description
The Bay Linear LM2940 & LM2941 is a 1.25A high accuracy, low dropout voltage regulator with only 40mV at light loads and 350mV(Typ.)@ 1.0A) and low quiescent current of 240A typical. The LM2940/41 is designed for low voltage a application that requires lower dropout voltage and faster transient response. This device is an excellent choice for use in powering low voltage applications where require a lower dropout, faster transient response to regulate from +2.5V to 3.8V supplies and as a post regulator for switching supplies applications. The LM2940/41 offers full protection against over-current faults, reversed input polarity, reversed load insertion, and positive and negative transient voltage. On-Chip trimming adjusts the reference voltage to 1%. The LM2940-xx devices are in 3 pin fixed voltage regulators. The LM2941 include an Enable pin in the 5 pin packages. The LM2940/41 are offered in a 3 & 5-pin SOT-223, TO-220 & TO-263 package compatible with other 3 terminal regulators. The LM2940/41 is also offer in a new LPDD (Low Profile TO-263) package from 4.47 mm (DD) tickness down to only 1.27 mm (LPDD) t t l ti k
Features
* * * * * * * * * High output accuracy of 1% Output Adjustable from 1.24V to 26V Output Current of 1.25A Low Dropout Voltage Low quiescent current Extremely Tight Load & Line Regulation Reverse-battery and "Load Dump" Protection Zero Current Shutdown Mode (5-pin version) Offer in TO-263, TO-220, SOT-223, & New Slim LPDD Similar to industry Standard MIC2940LM2941
*
Applications
* * * * * * * Powering VGA & Sound Card LCD Monitor Battery Powered Equipments/Laptop & Notebook SMPS Post Regulator / DC to DC Modules High Efficiency Linear Power Supply Adjustable Power Supply Bar Code Scanners
Pin Connection
Ordering Information
Devices
LM2940T LM2941T LM2940S LM2941S LM2940N LM2941N LM2940J LM2941J
TO-220-3 Package TO-220-5 Package TO-263-5 Package
BAY B2940 BAY BAY B2941 1 2345
B2941
Package
TO-220-3 TO-220-5 TO-263-3 TO-263-5 SOT-223-3 SOT-223-5 LPDD-3 LPDD-5
Temp.
-40 C to 125 C -40 C to 125 C -40 C to 125 C -40 C to 125 C -40 C to 125 C -40 C to 125 C -40 C to 125 C -40 C to 125 C
TO-263-3 Package
1) ADJUST 2) ON/OFF 3) GND 4) INPUT 5) OUPUT
BAY B2940 1 2 3
V IN
GND V OUT
V
IN
GND V
OUT
1 234 5
Front View
Front View
Top View
Top View
Bay Linear, Inc
2478 Armstrong Street, Livermore, CA 94550 Tel: (925) 989-7144, Fax: (925) 940-9556
www.baylinear.com
LM2940/41
ABSOLUTE MAXIMUM RATINGS
Lead Temp. (Soldering, 5 Seconds).................................260C Storage Temperature Range.............................. -65 to +150C Operating Junction Temperature Range LM2940/2941 Control Section.................. -45C +125C LM2940/2941 Power Transistor.................-45C +150C Input Voltage ........................................................26V Maximum Output Current....................................3.5A Input Supply Voltage (Note1) (Survival)-20V to +60V
ELECTRICAL CHARACTERISTICS (NOTE 1) at IOUT = 5mA, V IN =V OUT + 1V, I l = 1000mA, C L = 10F. Ta=25C, unless otherwise specified. The LM2941 is programmed to output 5V and has V SHUTDOWN 0.6V
PARAMETER
2.5V Version
CONDITIONS
IOUT = 5mA 5mA IOUT1.25A, 4.75VVIN 26V IOUT = 5mA 5mA IOUT1.25A, 4.75VVIN 26V IOUT = 5mA 5mA IOUT1.25A, 5.5VVIN 26V 5mA IOUT1.0 A IO = 5mA, (VOUT + 1V) VIN 26V VIN = VOUT + 5V, 5mA IOUT 1 A (Note 2, 6) Output Voltage (Note 6) Temperature Coef.
Typ Min
2.5 2.5 3.3 3.3 5.0 5.0 2.475 2.450 3.267 3.234 4.95 4.90 -1 -2 -2.5
LM2940 Max
2.525 2.550 3.330 3.366 5.05 5.10 1 2 2.5 0.5 1.6 100 150 450 600 350 35 70
Units
V
Output Voltage (Note 2)
3.3V Version2.
Output Voltage (Note 2)
5.0V Version
V
Output Voltage (Note 2) Output Voltage Accuracy
All Voltage Options
V %
Line Regulation Load Regulation V T Dropout Voltage
0.06 0.2 20 80 350 400 240 22 35 0.9 1.7 400 260 1.235 1.223 1.210 1.204 1.5
% % ppm/C mV
IO = 5mA IO = 1000mA IO = 1.25A
Ground Current IGNDDO Ground Pin Current at Dropout Current Limit Output Noise Voltage (10Hz to 100kHz) IL = 100mA Reference Voltage Reference Voltage Adjust Pin Bias Current Reference Voltage Temperature Coefficient Adjust Pin Bias Current Temperature Coefficient
IO = 5mA, VIN = VOUT, +1V IO = 1000mA, VIN = VOUT, +1V IO = 1.25A
VIN = 0.5V less than specified VOUT IOUT = 10mA VOUT = 0V (Note 4) CL = 10F CL = 33F
A mA mA A V RMS
(Note 8) 40 (Note 7) 20
1.247 1.260 1.266 80 120
V Vmax V nA ppm/C
0.1
nA/C
Bay Linear, Inc
2478 Armstrong Street, Livermore, CA 94550 Tel: (925) 989-7144, Fax: (925) 940-9556
www.baylinear.com
LM2940/2941
ENABLE Input LM2941
Input Logic Voltage Low (OFF) High (ON) V 0.8 2.4 VEN = 26V VEN = 0.8V (Note 10) 10 500 100 600 750 2.5 5 V A A
Enable Pin Input Current Regulator Output Current in Shutdown
NOTES:
The Bold specifications apply to the full operating temperature range. Note 1: Maximum positive supply voltage of 60V must be of limited duration (<100msec) and duty cycle.) The maximum continuous supply voltage is 26V. Note 2: Full load current (IFL) is defined as 1.25A for the LM2941. Note 3: Dropout voltage is defined as the input-to output differential when the output voltage drops to 99% of its nominal value with VOUT + 1V applied to VIN. Note 4: VIN = VOUT (NOMINAL) +1V. For example, use VIN= 4.3V for a 3.3V regulator. Employ pulse-testing procedures to minimize temperature rise. Note 5: Ground pin current is the regulator quiescent current. The total current drawn from the source is the sum of the load current to the ground current. Note 6: Output voltage temperature coefficient is defined as the worst case voltage changed divided by the total temperature range. Note 7: Thermal regulation is defined as the change in the output voltage at a time T after a change in power dissipation is applied, excluding load or line regulation effects. Specifications are for a 200mA load pulse as VIN = 20V (a 4W pulse) for T = 10ms. Note 8: VREF VOUT (VIN - 1), 2.3V VIN 26V, 10mA < IL IFL, TJ TJMAX Note 9: Comparator threshold is expressed in terms of a voltage differential at the Adjust terminal below the nominal reference voltage measured 6V input. To express these thresholds in terms of output voltage change, multiply the error amplifier gain = VOUT/VREF = (R1 + R2)/R2. For example, at a programmable output voltage of 5V, the Error output is guaranteed to go low when the output drops by 95mVx 5V/ 1.240V = 38mV. Threshold remains constant as a percent of VOUT as VOUT is varied, with the dropout warning occurring at typically 5% below nominal, 7.7% guaranteed. Note 10: VEN 0.8V and VIN 26V, VOUT = 0.
BLOCK DIAGRAM
IN
OUT
O.V ILIMIT
FLAG
+ -
1.180V
Reference
1.240V
+ -
28V
R1*
ADJ EN
Thermal Shutdown
R2*
GND
Bay Linear, Inc
2478 Armstrong Street, Livermore, CA 94550 Tel: (925) 989-7144, Fax: (925) 940-9556
www.baylinear.com
LM2940/2941
APPLICATION HINTS
The Bay Linear LM2941 incorporates protection against over-current faults, reversed load insertion, over temperature operation, and positive and negative transient voltage. However, the use of an output capacitor is required in order to insure the stability and the performances.
Minimum Load Current
To ensure a proper behavior of the regulator at light load, a minimum load of 5mA for LM2941 is required.
Adjustable Regulator Design
B29152/53 are adjustable regulators and maybe programmed for any value between 1.25V and 26V using two resistors. The relation between the resistors is given by: R1=R2 (VOUT/1.240 -1) Resistors have a large value up to 1m in order to reduce the current consumption. This might be interesting in the case of widely varying load currents.
Thermal Consideration
Although the LM2941 offers limiting circuitry for overload conditions, it is necessary not to exceed the maximum junction temperature, and therefore to be careful about thermal resistance. The heat flow will follow the lowest resistance path, which is the Junctionto-case thermal resistance. In order to insure the best thermal flow of the component, a proper mounting is required. Note that the case of the device is electrically connected to the output. The case has to be electrically isolated, a thermally conductive spacer can be used. However do not forget to consider its contribution to thermal resistance. Assuming: VIN = 10V, VOUT = 5V, IOUT = 1.5A, TA = 90C, CASE= 1C/W (no external heat sink, no wind) Power dissipation under these conditions PD = (VIN - VOUT) * IOUT = 7.5W Junction Temperature TJ = TA + PD * (CASE+ JC) For the Control Section TJ = 90C + 7.5W*(1C/W + 0.6C/W) = 102C 114C < TJUNCTION MAX for the control section. For the Power Section TJ = 90C + 7.5W*(1C/W + 1.6C/W) = 104.5C 109.5C < TJUNCTION MAX for the power transistor. In both case reliable operation is insured by adequate junction temperature.
Enable Input
LM2941 features enable input allowing turning ON & OFF the device. EN has been designed to be compatible with TTL/CMOS logic. When the regulator is ON, the current flowing through this pin is approximately 20A.
VIN
BAY B2940
V OU
T
Fig.1 Basic Fixed Output Regulator
Capacitor Requirements
The output capacitor is needed for stability and to minimize the output noise. The required value of the capacitor varies with the load. However, a minimum value of 10F Aluminum will guarantee stability over load. A tantalum capacitor is recommended for a fast load transient response. If the power source has high AC impedance, a 0.1F capacitor between input & ground is recommended. This capacitor should have good characteristics up to 250 kHz.
1 2 4 5
VIN
BAY B2941
3
VOUT R1
VOUT = VREF X [1 + (R1/ R2)]
enough to pass the minimum regulator load current
R2
For best results, the total series resistance should be small
Fig. 2 Adjustable Output Voltage Regulator
Bay Linear, Inc
2478 Armstrong Street, Livermore, CA 94550 Tel: (925) 989-7144, Fax: (925) 940-9556
www.baylinear.com
LM2940/2941
Advance Information- These data sheets contain descriptions of products that are in development. The specifications are based on the engineering calculations, computer simulations and/ or initial prototype evaluation. Preliminary Information- These data sheets contain minimum and maximum specifications that are based on the initial device characterizations. These limits are subject to change upon the completion of the full characterization over the specified temperature and supply voltage ranges.
The application circuit examples are only to explain the representative applications of the devices and are not intended to guarantee any circuit design or permit any industrial property right to other rights to execute. Bay Linear takes no responsibility for any problems related to any industrial property right resulting from the use of the contents shown in the data book. Typical parameters can and do vary in different applications. Customer's technical experts must validate all operating parameters including " Typical" for each customer application.
LIFE SUPPORT AND NUCLEAR POLICY Bay Linear products are not authorized for and should not be used within life support systems which are intended for surgical implants into the body to support or sustain life, in aircraft, space equipment, submarine, or nuclear facility applications without the specific written consent of Bay Linear President.
Bay Linear, Inc
2478 Armstrong Street, Livermore, CA 94550 Tel: (925) 989-7144, Fax: (925) 940-9556
www.baylinear.com

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