SNVS099I May   1999  – October 2016 LM2991

PRODUCTION DATA.  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
  4. 4 Revision History
  5. 5 Pin Configuration and Functions
  6. 6 Specifications
    1. 6.1 Absolute Maximum Ratings
    2. 6.2 ESD Ratings
    3. 6.3 Recommended Operating Conditions
    4. 6.4 Thermal Information
    5. 6.5 Electrical Characteristics
    6. 6.6 Typical Characteristics
  7. 7 Detailed Description
    1. 7.1 Overview
    2. 7.2 Functional Block Diagram
    3. 7.3 Feature Description
      1. 7.3.1 ON/Off Pin
      2. 7.3.2 Forcing The Output Positive
      3. 7.3.3 Thermal Shutdown
    4. 7.4 Device Functional Modes
      1. 7.4.1 Operation with VOUT(TARGET) -5 V ≥ VIN > -26 V
  8. 8 Application and Implementation
    1. 8.1 Application Information
    2. 8.2 Typical Application
      1. 8.2.1 Design Requirements
      2. 8.2.2 Detailed Design Procedure
        1. 8.2.2.1 External Capacitors
          1. 8.2.2.1.1 Input Capacitor
          2. 8.2.2.1.2 Output Capacitor
        2. 8.2.2.2 Ceramic Bypass Capacitors
        3. 8.2.2.3 Minimum Load
        4. 8.2.2.4 Setting The Output Voltage
        5. 8.2.2.5 Power Dissipation
        6. 8.2.2.6 Estimating Junction Temperature
      3. 8.2.3 Application Curves
      4. 8.2.4 Additional Application Circuits
  9. 9 Power Supply Recommendations
  10. 10Layout
    1. 10.1 Layout Guidelines
    2. 10.2 Layout Example
  11. 11Device and Documentation Support
    1. 11.1 Device Support
      1. 11.1.1 Device Nomenclature
    2. 11.2 Related Documentation
    3. 11.3 Receiving Notification of Documentation Updates
    4. 11.4 Community Resources
    5. 11.5 Trademarks
    6. 11.6 Electrostatic Discharge Caution
    7. 11.7 Glossary
  12. 12Mechanical, Packaging, and Orderable Information

Package Options

Mechanical Data (Package|Pins)
Thermal pad, mechanical data (Package|Pins)
Orderable Information

1 Features

  • 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) 10.20 mm × 9.00 mm
TO-220 (5) 14.99 mm × 10.16 mm
  1. For all available packages, see the orderable addendum at the end of the data sheet.

Typical Application

LM2991 1126001.gif
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.