SLVSBB2F May   2012  – August 2024 TPS65131-Q1

PRODUCTION DATA  

  1.   1
  2. 1 Features
  3. 2 Applications
  4. 3 Description
  5. 4 Device Comparison
  6. 5 Pin Configuration and Functions
  7. 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
  8. 7 Detailed Description
    1. 7.1 Overview
    2. 7.2 Functional Block Diagram
    3. 7.3 Feature Description
      1. 7.3.1 Power Conversion
      2. 7.3.2 Control
      3. 7.3.3 Output Rails Enable or Disable
      4. 7.3.4 Load Disconnect
      5. 7.3.5 Soft Start
      6. 7.3.6 Overvoltage Protection
      7. 7.3.7 Undervoltage Lockout
      8. 7.3.8 Overtemperature Shutdown
    4. 7.4 Device Functional Modes
      1. 7.4.1 Power-Save Mode
  9. 8 Application and Implementation
    1. 8.1 Application Information
    2. 8.2 Typical Applications
      1. 8.2.1 TPS65131-Q1 With VPOS = 10.5V, VNEG = –10V
      2. 8.2.2 Design Requirements
      3. 8.2.3 Detailed Design Procedure
        1. 8.2.3.1 Programming the Output Voltage
          1. 8.2.3.1.1 Boost Converter
          2. 8.2.3.1.2 Inverting Converter
          3. 8.2.3.1.3 Inductor Selection
        2. 8.2.3.2 Capacitor Selection
          1. 8.2.3.2.1 Input Capacitor
          2. 8.2.3.2.2 Output Capacitors
        3. 8.2.3.3 Rectifier Diode Selection
        4. 8.2.3.4 External P-MOSFET Selection
        5. 8.2.3.5 Stabilizing the Control Loop
          1. 8.2.3.5.1 Feedforward Capacitors
          2. 8.2.3.5.2 Compensation Capacitors
      4. 8.2.4 Analog Supply Input Filter
        1. 8.2.4.1 RC-Filter
        2. 8.2.4.2 LC-Filter
      5. 8.2.5 Thermal Information
      6. 8.2.6 Application Curves
    3. 8.3 Power Supply Recommendations
    4. 8.4 Layout
      1. 8.4.1 Layout Guidelines
      2. 8.4.2 Layout Example
  10. 9 Device and Documentation Support
    1. 9.1 Receiving Notification of Documentation Updates
    2. 9.2 Support Resources
    3. 9.3 Trademarks
    4. 9.4 Electrostatic Discharge Caution
    5. 9.5 Glossary
  11. 10Revision History
  12. 11Mechanical, Packaging, and Orderable Information
    1. 11.1 Mechanical Data
    2. 11.2 Tape and Reel Information
8.2.3.5.1 Feedforward Capacitors

As a recommendation, to speed up the control loop, place feedforward capacitors in the feedback divider, parallel to R1 (boost converter) and R3 (inverting converter). Equation 11 shows how to calculate the appropriate value for the boost converter, and Equation 12 for the inverting converter.

Equation 11. TPS65131-Q1
Equation 12. TPS65131-Q1

In this application example, C9 = 6.8pF and C10 = 7.5pF match the choices of R1 and R3.

To avoid coupling noise into the control loop from the feedforward capacitors, it is possible to place a series resistor to limit the bandwidth of the feedforward effect. Any value between 10kΩ and 100kΩ is suitable. The higher the resistance, the lower the noise coupled into the control loop system.