SLVSD88M July   2016  – August 2026 TPS61099

PRODMIX  

  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 Boost Controller Operation
      2. 7.3.2 Undervoltage Lockout
      3. 7.3.3 Enable and Disable
      4. 7.3.4 Soft Start
      5. 7.3.5 Current Limit Operation
      6. 7.3.6 Output Short-to-Ground Protection
      7. 7.3.7 Overvoltage Protection
      8. 7.3.8 Down Mode Regulation and Pass-Through Operation
      9. 7.3.9 Thermal Shutdown
    4. 7.4 Device Functional Modes
      1. 7.4.1 Burst Mode Operation under Light Load Condition
      2. 7.4.2 Down Mode Regulation and Pass-Through Mode Operation
  9. 8 Application and Implementation
    1. 8.1 Application Information
    2. 8.2 Typical Application - 5V Output Boost Converter
      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 Programming the Output Voltage
        3. 8.2.2.3 Maximum Output Current
        4. 8.2.2.4 Inductor Selection
        5. 8.2.2.5 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. 9.1.2 Development Support
        1. 9.1.2.1 Custom Design With WEBENCH® Tools
    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

7.3.4 Soft Start

After the EN pin is tied to high voltage, the TPS61099x begins to start up. At the beginning, the device operates at the boundary of Discontinuous Conduction Mode (DCM) and Continuous Conduction Mode (CCM), and the inductor peak current is limited to around 200mA during this stage. When the output voltage is charged above approximately 1.6V, the device starts the hysteretic current mode operation. The current limit threshold is gradually increasing to 0.7 × ILIM within 500µs. In this way, the soft-start function reduces the inrush current during start-up. After VOUT reaches the target value, soft start stage ends and the peak current is now determined by the output of an internal error amplifier which compares the feedback of the output voltage and the internal reference voltage.

The TPS61099x is able to start up with 0.7V input voltage with larger than 3kΩ load. However, if the load during start-up is so heavy that the TPS61099x fails to charge the output voltage above 1.6V, the TPS61099x cannot start up successfully until the input voltage is increased or the load current is reduced. The start-up time depends on input voltage and load current.

For fixed‑output devices, the target output voltage is set through EEPROM. During an EN ON‑OFF‑ON transition, the EEPROM bits are temporarily cleared to zero before the correct configuration is reloaded. To ensure reliable EEPROM bit restoration, avoid excessively short EN off‑periods and keep the EN low‑time at least 400µs for any ON‑OFF‑ON transition.