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LM2991 Datasheet

Negative Low-Dropout Adjustable Regulator

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LM2991
SNVS099I – MAY 1999 – REVISED OCTOBER 2016
LM2991 Negative Low-Dropout Adjustable Regulator
1 Features
1 Output Voltage Adjustable from 3 V to 24 V,
Typically 2 V to 25 V
• Output Current in Excess of 1 A
• Dropout Voltage Typically 0.6 V at 1-A Load
• Low Quiescent Current
• Internal Short Circuit Current Limit
• Internal Thermal Shutdown With Hysteresis
• TTL, CMOS Compatible ON/OFF Switch
• Functional Complement to the LM2941 Series
2 Applications
• Post Switcher Regulator
• Local, On-Card, Regulation
• Battery Operated Equipment
• Industrial
• Instrumentation
3 Description
The LM2991 is a low dropout adjustable negative
regulator with a output voltage range between 3 V to
24 V. The LM2991 provides up to 1 A of load
current and features a ON /OFF pin for remote
shutdown capability.
The LM2991 uses new circuit design techniques to
provide a low dropout voltage, low quiescent current
and low temperature coefficient precision reference.
The dropout voltage at 1-A load current is typically
0.6 V and an ensured worst-case maximum of 1 V
over the entire operating temperature range. The
quiescent current is typically 1 mA with a 1-A load
current and an input-output voltage differential greater
than 3 V. A unique circuit design of the internal bias
supply limits the quiescent current to only 9 mA
(typical) when the regulator is in the dropout mode
(VOUT VIN 3 V).
The LM2991 is short-circuit proof, and thermal
shutdown includes hysteresis to enhance the
reliability of the device when inadvertently overloaded
for extended periods. The LM2991 is available in 5-
lead TO-220 and DDPAK/TO-263 packages and is
rated for operation over the automotive temperature
range of 40°C to +125°C. Mil-Aero versions are also
available.
Device Information(1)
PART NUMBER
PACKAGE
BODY SIZE (NOM)
LM2991
DDPAK/TO-263 (5)
TO-220 (5)
10.20 mm × 9.00 mm
14.99 mm × 10.16 mm
(1) For all available packages, see the orderable addendum at
the end of the data sheet.
Typical Application
GND
+ CIN*
ADJ
R1
+
COUT**
Unregulated
IN
Input
ON/OFF
LM2991
OUT R2
Regulated
Input
Copyright © 2016, Texas Instruments Incorporated
VOUT = VREF (1 + R2/R1)
* Required if the regulator is located further than 6 inches from the power supply filter capacitors. A 1-μF solid
tantalum or a 10-μF aluminum electrolytic capacitor is recommended.
** Required for stability. Must be at least a 10-μF aluminum electrolytic or a 1-μF solid tantalum to maintain stability.
May be increased without bound to maintain regulation during transients. Locate the capacitor as close as possible to
the regulator. The equivalent series resistance (ESR) is critical, and should be less than 10Ω over the same operating
temperature range as the regulator.
1
An IMPORTANT NOTICE at the end of this data sheet addresses availability, warranty, changes, use in safety-critical applications,
intellectual property matters and other important disclaimers. PRODUCTION DATA.




etcTI

LM2991 Datasheet Preview

LM2991 Datasheet

Negative Low-Dropout Adjustable Regulator

No Preview Available !

LM2991
SNVS099I – MAY 1999 – REVISED OCTOBER 2016
www.ti.com
Table of Contents
1 Features .................................................................. 1
2 Applications ........................................................... 1
3 Description ............................................................. 1
4 Revision History..................................................... 2
5 Pin Configuration and Functions ......................... 3
6 Specifications......................................................... 4
6.1 Absolute Maximum Ratings ...................................... 4
6.2 ESD Ratings.............................................................. 4
6.3 Recommended Operating Conditions....................... 4
6.4 Thermal Information .................................................. 4
6.5 Electrical Characteristics........................................... 5
6.6 Typical Characteristics .............................................. 6
7 Detailed Description .............................................. 9
7.1 Overview ................................................................... 9
7.2 Functional Block Diagram ......................................... 9
7.3 Feature Description................................................... 9
7.4 Device Functional Modes........................................ 10
8 Application and Implementation ........................ 11
8.1 Application Information............................................ 11
8.2 Typical Application ................................................. 11
9 Power Supply Recommendations...................... 15
10 Layout................................................................... 16
10.1 Layout Guidelines ................................................. 16
10.2 Layout Example .................................................... 16
11 Device and Documentation Support ................. 17
11.1 Device Support .................................................... 17
11.2 Related Documentation ....................................... 17
11.3 Receiving Notification of Documentation Updates 17
11.4 Community Resources.......................................... 17
11.5 Trademarks ........................................................... 17
11.6 Electrostatic Discharge Caution ............................ 18
11.7 Glossary ................................................................ 18
12 Mechanical, Packaging, and Orderable
Information ........................................................... 18
4 Revision History
NOTE: Page numbers for previous revisions may differ from page numbers in the current version.
Changes from Revision H (June 2013) to Revision I
Page
• Added Device Information and ESD Rating tables, Feature Description, Device Functional Modes, Application and
Implementation, Power Supply Recommendations, Layout, Device and Documentation Support, and Mechanical,
Packaging, and Orderable Information sections; moved some curves to Application Curves section .................................. 1
• Changed footnote 4 of Abs Max table and footnote 1 to Typical Characteristics to eliminate obsolete thermal values
for thetaJA; updated values are in Thermal Information ....................................................................................................... 4
• Changed Figure 14 as previous thermal values have been updated .................................................................................... 8
Changes from Revision G (April 2013) to Revision H
Page
• Changed layout of National Semiconductor data sheet to TI format...................................................................................... 1
2
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Copyright © 1999–2016, Texas Instruments Incorporated



Part Number LM2991
Description Negative Low-Dropout Adjustable Regulator
Maker etcTI
Total Page 3 Pages
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