SLVSIH2 May   2026 TPS61129-Q1

ADVMIX  

  1.   1
  2. 1 Features
  3. 2 Applications
  4. 3 Description
  5. 4 Device Comparison Table
  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 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 Synchronous Rectifier and True Shutdown
      2. 7.3.2 Device Enable
      3. 7.3.3 Down Mode Threshold
      4. 7.3.4 SYNC/MODE Configuration
      5. 7.3.5 Output Discharge
      6. 7.3.6 Soft Start and Short-Circuit Protection
      7. 7.3.7 Power-Good Indicator
      8. 7.3.8 Spread Spectrum Frequency Modulation
    4. 7.4 Device Functional Modes
      1. 7.4.1 Undervoltage Lockout
    5. 7.5 Programming
      1. 7.5.1 Programming the Output Voltage
  9. 8 Application and Implementation
    1. 8.1 Application Information
    2. 8.2 Typical Application
      1. 8.2.1 Design Requirements
      2. 8.2.2 Detailed Design Procedure
        1. 8.2.2.1 Inductor Selection
        2. 8.2.2.2 Input Capacitor Selection
        3. 8.2.2.3 Output Capacitor Selection
      3. 8.2.3 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 Device Support
      1. 9.1.1 Third-Party Products Disclaimer
    2. 9.2 Documentation Support
      1. 9.2.1 Related Documentation
    3. 9.3 Receiving Notification of Documentation Updates
    4. 9.4 Support Resources
    5. 9.5 Trademarks
    6. 9.6 Electrostatic Discharge Caution
    7. 9.7 Glossary
  11. 10Revision History
  12. 11Mechanical, Packaging, and Orderable Information
    1. 11.1 Tape and Reel Information

7.5.1 Programming the Output Voltage

The output voltage of the TPS61129-Q1 can be adjusted with an external resistor divider. The typical value of the voltage at the FB pin is 500mV. The maximum recommended value for the output voltage is 5.5V. The output voltage is set by an external resistor divider (R1, R2 in the TPS61129-Q1 Typical Schematic for Fixed 5V or Adjustable Output figure). When the output voltage is regulated, the typical voltage at the FB pin is VREF. Therefore, use Equation 1 to calculate the resistor divider.

Equation 1. TPS61129-Q1

where

  • VOUT is the regulated output voltage
  • VREF is the internal reference voltage at the FB pin, 0.5V typically

The current through the resistive divider must be about 100 times greater than the current into the FB pin. The typical current into the FB pin is 4nA, and the voltage across R2 is typically 500mV. For the best accuracy, keep R2 smaller than 300kΩ to make sure the current flowing through R2 is at least 100 times larger than the FB pin leakage current. Changing R2 toward a lower value increases the immunity against noise injection. Changing the R2 toward a higher value reduces the quiescent current for achieving highest efficiency at low load currents.