SNVSAH3E February   2018  – July 2020 LMR23625

PRODUCTION DATA  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
  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 Timing Requirements
    7. 6.7 Switching Characteristics
    8. 6.8 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 Fixed-Frequency Peak-Current-Mode Control
      2. 7.3.2 Adjustable Output Voltage
      3. 7.3.3 Enable/Sync
      4. 7.3.4 VCC, UVLO
      5. 7.3.5 Minimum ON-time, Minimum OFF-time and Frequency Foldback at Drop-out Conditions
      6. 7.3.6 Internal Compensation and CFF
      7. 7.3.7 Bootstrap Voltage (BOOT)
      8. 7.3.8 Overcurrent and Short-Circuit Protection
      9. 7.3.9 Thermal Shutdown
    4. 7.4 Device Functional Modes
      1. 7.4.1 Shutdown Mode
      2. 7.4.2 Active Mode
      3. 7.4.3 CCM Mode
      4. 7.4.4 Light Load Operation (PFM Option)
      5. 7.4.5 Light Load Operation (FPWM Option)
  8. 8 Application and Implementation
    1. 8.1 Application Information
    2. 8.2 Typical Applications
      1. 8.2.1 Design Requirements
      2. 8.2.2 Detailed Design Procedure
        1. 8.2.2.1  Custom Design With WEBENCH® Tools
        2. 8.2.2.2  Output Voltage Setpoint
        3. 8.2.2.3  Switching Frequency
        4. 8.2.2.4  Inductor Selection
        5. 8.2.2.5  Output Capacitor Selection
        6. 8.2.2.6  Feed-forward Capacitor
        7. 8.2.2.7  Input Capacitor Selection
        8. 8.2.2.8  Bootstrap Capacitor Selection
        9. 8.2.2.9  VCC Capacitor Selection
        10. 8.2.2.10 Undervoltage Lockout Set-Point
      3. 8.2.3 Application Curves
  9. 9 Power Supply Recommendations
  10. 10Layout
    1. 10.1 Layout Guidelines
    2. 10.2 Layout Example
    3. 10.3 Compact Layout for EMI Reduction
    4. 10.4 Ground Plane and Thermal Considerations
    5. 10.5 Feedback Resistors
  11. 11Device and Documentation Support
    1. 11.1 Device Support
      1. 11.1.1 Development Support
        1. 11.1.1.1 Custom Design With WEBENCH® Tools
    2. 11.2 Receiving Notification of Documentation Updates
    3. 11.3 Support Resources
    4. 11.4 Trademarks
    5. 11.5 Electrostatic Discharge Caution
    6. 11.6 Glossary
  12. 12Mechanical, Packaging, and Orderable Information

Package Options

Refer to the PDF data sheet for device specific package drawings

Mechanical Data (Package|Pins)
  • DDA|8
  • DRR|12
Thermal pad, mechanical data (Package|Pins)
Orderable Information

7.3.2 Adjustable Output Voltage

A precision 1-V reference voltage is used to maintain a tightly regulated output voltage over the entire operating temperature range. The output voltage is set by a resistor divider from output voltage to the FB pin. TI recommends using 1% tolerance resistors with a low temperature coefficient for the FB divider. Select the low-side resistor RFBB for the desired divider current and use Equation 1 to calculate high-side RFBT. RFBT in the range from 10 kΩ to 100 kΩ is recommended for most applications. A lower RFBT value can be used if static loading is desired to reduce VOUT offset in PFM operation. Lower RFBT will reduce efficiency at very light load. Less static current goes through a larger RFBT and might be more desirable when light load efficiency is critical. However, RFBT larger than 1 MΩ is not recommended because it makes the feedback path more susceptible to noise. Larger RFBT value requires more carefully designed feedback path on the PCB. The tolerance and temperature variation of the resistor dividers affect the output voltage regulation.

GUID-C8D64800-62AC-4CF9-96E9-039CC4AA61E1-low.gifFigure 7-2 Output Voltage Setting
Equation 1. GUID-9868F81E-4D91-4A3C-8ABA-1A550290218E-low.gif