Bay Linear
Inspire the Linear Power
1.25A High Current Low Dropout
Voltage Regulator for Convert 5V & 3.3V
LM3940
Description
The Bay Linear LM3940 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 240µA typical.
The LM3940 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 LM3940 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 LM3940 are offered in a 3-pin SOT-223, TO-220 & TO-263
package compatible with other 3 terminal regulators. The LM3940
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) total
tickness.
Features
•
•
•
•
•
•
•
•
•
High output accuracy of 1%
Fix Output 5.0v & 3.3V
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-252, TO-220, SOT-223, &
New Slim LPDD
Similar to industry Standard LM3940
•
Applications
•
•
•
•
•
•
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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
LM3940T
LM3940S
LM3940D
LM3940N
LM3940J
XX=Output Voltage
Package
TO-220-3
TO-263-3
TO-252
SOT-223-3
LPDD-3
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
Bay Linear, Inc
2478 Armstrong Street, Livermore, CA 94550 Tel: (925) 989-7144, Fax: (925) 940-9556
www.baylinear.com
LM3940
ABSOLUTE MAXIMUM RATINGS
Lead Temp. (Soldering, 5 Seconds).................................260°C
Storage Temperature Range.............................. -65° to +150°C
Operating Junction Temperature Range
LM3940 Control Section........................... -45°C +125°C
LM3940 Power Transistor..........................-45°C +150°C
Input Voltage ........................................................26V
Maximum Output Current....................................3.5A
Input Supply Voltage (Survival) .......... -20V to +60V
ELECTRICAL CHARACTERISTICS
PARAMETER
Output Voltage
Output Voltage
Line Regulation
Load Regulation
Dropout Voltage
5mA≤I
L
≤1.25A
5mA≤I
L
≤1.25A
I
OUT
= 5mA, V
IN
=V
OUT
+ 1V, I
l
= 1250mA, C
L
= 10µF. Ta=25°C, unless otherwise specified.
CONDITIONS
Typ
Min
3.3
3.3
5.0
5.0
20
35
120
400
500
240
22
35
1.7
1.7
400
260
1.2
1.5
3.267
3.234
4.95
4.90
LM3940
Max
3.330
3.366
5.05
5.10
40
50
180
600
800
350
35
70
Units
V
V
mV
mV
mV
I
O
= 5mA, 4.5V≤V
IN
≤5.5V
50mA
≤
I
OUT
≤
1.25 A
I
O
= 5mA
I
O
= 1000mA
I
O
= 1250mA
Quiescent Current
Short Circuit Current
Current Limit
Output Noise Voltage
(10Hz to 100kHz)
I
L
= 100mA
I
O
= 5mA, V
IN
= V
OUT
, +1V
I
O
= 1000mA, V
IN
= V
OUT
, +1V
I
O
= 1.25A
R
L
= 0
V
OUT
= 0V (Note 4)
C
L
= 10µF
C
L
= 33µF
µA
mA
A
A
µV
RMS
BLOCK DIAGRAM
Bay Linear, Inc
2478 Armstrong Street, Livermore, CA 94550 Tel: (925) 989-7144, Fax: (925) 940-9556
www.baylinear.com
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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