SNVSA56B May   2015  – February 2017 LM2776

PRODUCTION DATA.  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
    1.     Device Images
      1.      Typical Application
      2.      Output Impedance vs Input Voltage IOUT = 100 mA
  4. 4 Revision History
  5. 5 Pin Configuration and Functions
    1.     Pin 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 Switching Characteristics
    7. 6.7 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 Input Current Limit
      2. 7.3.2 PFM Operation
      3. 7.3.3 Output Discharge
      4. 7.3.4 Thermal Shutdown
      5. 7.3.5 Undervoltage Lockout
    4. 7.4 Device Functional Modes
      1. 7.4.1 Shutdown Mode
      2. 7.4.2 Enable Mode
  8. 8 Application and Implementation
    1. 8.1 Application Information
    2. 8.2 Typical Application - Voltage Inverter
      1. 8.2.1 Design Requirements
      2. 8.2.2 Detailed Design Requirements
        1. 8.2.2.1 Efficiency
        2. 8.2.2.2 Power Dissipation
        3. 8.2.2.3 Capacitor Selection
        4. 8.2.2.4 Output Capacitor and Output Voltage Ripple
        5. 8.2.2.5 Input Capacitor
        6. 8.2.2.6 Flying Capacitor
      3. 8.2.3 Application Curve
  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 Third-Party Products Disclaimer
    2. 11.2 Receiving Notification of Documentation Updates
    3. 11.3 Community Resources
    4. 11.4 Trademarks
    5. 11.5 Electrostatic Discharge Caution
    6. 11.6 Glossary
  12. 12Mechanical, Packaging, and Orderable Information

8.2.2.6 Flying Capacitor

The flying capacitor (C1) transfers charge from the input to the output. Flying capacitance can impact both output current capability and ripple magnitudes. If flying capacitance is too small, the LM2776 may not be able to regulate the output voltage when load currents are high. On the other hand, if the flying capacitance is too large, the flying capacitor might overwhelm the input and output capacitors, resulting in increased input and output ripple.

In typical high-current applications, TI recommends 0.47-µF or 1-µF 10 V low-ESR ceramic capacitors for the flying capacitors. Polarized capacitors (tantalum, aluminum electrolytic, etc.) must not be used for the flying capacitor, as they could become reverse-biased during LM2776 operation.