SNVS018AB March   2000  – June 2025 LP2985-N

PRODUCTION DATA  

  1.   1
  2. 1 Features
  3. 2 Applications
  4. 3 Description
  5. 4 Pin Configuration and Functions
  6. 5 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. 6 Detailed Description
    1. 6.1 Overview
    2. 6.2 Functional Block Diagrams
    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 Output Pulldown
      6. 6.3.6 Thermal Shutdown
    4. 6.4 Device Functional Modes
      1. 6.4.1 Normal Operation
      2. 6.4.2 Dropout Operation
      3. 6.4.3 Disabled
  8. 7 Application and Implementation
    1. 7.1 Application Information
      1. 7.1.1 Recommended Capacitor Types
        1. 7.1.1.1 Recommended Capacitors (Legacy Chip)
        2. 7.1.1.2 Recommended Capacitors (New Chip)
      2. 7.1.2 Input Capacitor Requirements
      3. 7.1.3 Output Capacitor Requirements
      4. 7.1.4 Noise Bypass Capacitor (CBYPASS)
      5. 7.1.5 Reverse Current
      6. 7.1.6 Power Dissipation (PD)
      7. 7.1.7 Estimating Junction Temperature
    2. 7.2 Typical Application
      1. 7.2.1 Design Requirements
      2. 7.2.2 Detailed Design Procedure
        1. 7.2.2.1 ON/OFF Input Operation
      3. 7.2.3 Application Curves
    3. 7.3 Power Supply Recommendations
    4. 7.4 Layout
      1. 7.4.1 Layout Guidelines
      2. 7.4.2 Layout Example
  9. 8 Device and Documentation Support
    1. 8.1 Documentation Support
      1. 8.1.1 Related Documentation
    2. 8.2 Device Nomenclature
    3. 8.3 Receiving Notification of Documentation Updates
    4. 8.4 Support Resources
    5. 8.5 Trademarks
    6. 8.6 Electrostatic Discharge Caution
    7. 8.7 Glossary
  10. 9 Revision History
  11. 10Mechanical, Packaging, and Orderable Information

7.1.2 Input Capacitor Requirements

For legacy chip, an input capacitor whose capacitance is ≥ 1µF is required between the LP2985-N input and ground (increase the amount of capacitance without limit). Place this capacitor no more than 1cm from the input pin and make sure the capacitor returns to a clean analog ground. Use any good-quality ceramic, tantalum, or film capacitor at the input.

Note:

Tantalum capacitors can suffer catastrophic failure because of surge current when connected to a low-impedance source of power (such as a battery or very large capacitor). If a tantalum capacitor is used at the input, contact the manufacturer to make sure the capacitor has a surge current rating sufficient for the application.

There are no requirements for ESR on the input capacitor, but consider tolerance and temperature coefficient when selecting the capacitor to make sure the capacitance is ≥ 1µF over the entire operating temperature range.

For new chip, although an input capacitor is not required for stability, good analog design practice is to connect a capacitor from IN to GND. This capacitor counteracts reactive input sources and improves transient response, input ripple, and PSRR. Use an input capacitor if the source impedance is more than 0.5Ω. A higher value capacitor can be necessary if large, fast rise-time load or line transients are anticipated or if the device is located several inches from the input power source.