SNOS773O March   2000  – December 2023 LP2981-N

PRODUCTION DATA  

  1.   1
  2. Features
  3. Applications
  4. Description
  5. Pin Configuration and Functions
  6. Specifications
    1. 5.1 Absolute Maximum Ratings
    2. 5.2 ESD Ratings
    3. 5.3 Recommended Operating Conditions
    4. 5.4 Thermal Information
    5. 5.5 Electrical Characteristics
    6. 5.6 Typical Characteristics
  7. Detailed Description
    1. 6.1 Overview
    2. 6.2 Functional Block Diagram
    3. 6.3 Feature Description
      1. 6.3.1 Output Enable
      2. 6.3.2 Dropout Voltage
      3. 6.3.3 Current Limit
      4. 6.3.4 Undervoltage Lockout (UVLO)
      5. 6.3.5 Thermal Shutdown
      6. 6.3.6 Output Pulldown
    4. 6.4 Device Functional Modes
      1. 6.4.1 Device Functional Mode Comparison
      2. 6.4.2 Normal Operation
      3. 6.4.3 Dropout Operation
      4. 6.4.4 Disabled
  8. Application and Implementation
    1. 7.1 Application Information
      1. 7.1.1 Recommended Capacitor Types
        1. 7.1.1.1 Recommended Capacitors for the Legacy Chip
        2. 7.1.1.2 Recommended Capacitors for the New Chip
      2. 7.1.2 Input and Output Capacitor Requirements
      3. 7.1.3 Estimating Junction Temperature
      4. 7.1.4 Power Dissipation (PD)
      5. 7.1.5 Reverse Current
    2. 7.2 Typical Application
      1. 7.2.1 Design Requirements
      2. 7.2.2 Detailed Design Procedure
        1. 7.2.2.1 ON and OFF Input Operation
      3. 7.2.3 Application Curves
  9. Power Supply Recommendations
  10. Layout
    1. 9.1 Layout Guidelines
    2. 9.2 Layout Example
  11. 10Device and Documentation Support
    1. 10.1 Device Nomenclature
    2. 10.2 Third-Party Products Disclaimer
    3. 10.3 Receiving Notification of Documentation Updates
    4. 10.4 Related Documentation
    5. 10.5 Support Resources
    6. 10.6 Trademarks
    7. 10.7 Electrostatic Discharge Caution
    8. 10.8 Glossary
  12. 11Revision History
  13. 12Mechanical, Packaging, and Orderable Information

Package Options

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

Recommended Capacitors for the Legacy Chip

Tantalum Capacitors: For the legacy chip LP2981-N, tantalum capacitors are the best choice for use at the output of the LDO. Most good quality tantalums can be used with the LP2981-N, but check the manufacturer's data sheet to be sure the ESR is in range. At lower temperatures, as ESR increases, a capacitor with ESR, near the upper limit for stability at room temperature can cause instability. For very low temperature applications, output tantalum capacitors can be used in parallel configuration to prevent the ESR from going up too high.

Ceramic Capacitors: For the legacy chip LP2981-N, ceramic capacitors are not recommended for use at the output of the LDO. This is because the ESR of a ceramic can be low enough to go below the minimum stable value for the LP2981-N. A 2.2-μF ceramic was measured and found to have an ESR of about 15 mΩ, which is low enough to cause oscillations.If a ceramic capacitor is used on the output, a 1-Ω resistor is required be placed in series with the capacitor.

Aluminum Capacitors: For the legacy chip LP2981-N, aluminum electrolytics are not typically used with the LDO, because of the large physical size. These aluminimum capacitors must meet the same ESR requirements over the operating temperature range, more difficult because of their steep increase at cold temperature. An aluminum electrolytic can exhibit an ESR increase of as much as 50x when going from 20°C to −40°C. Also, some aluminum electrolytics are not operational below −25°C because the electrolyte can freeze.