SLVSB50C December   2011  – June 2020 TPS61087-Q1

PRODUCTION DATA.  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
    1.     Device Images
      1.      Simplified Schematic
  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 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 Soft Start
      2. 7.3.2 Frequency Select Pin (FREQ)
      3. 7.3.3 Undervoltage Lockout (UVLO)
      4. 7.3.4 Thermal Shutdown
      5. 7.3.5 Overvoltage Prevention
    4. 7.4 Device Functional Modes
  8. 8 Application and Implementation
    1. 8.1 Application Information
    2. 8.2 Typical Applications
      1. 8.2.1 Typical Application Circuit: 5 V to 15 V (fS = 1.2 MHz)
        1. 8.2.1.1 Design Requirements
        2. 8.2.1.2 Detailed Design Procedure
          1. 8.2.1.2.1 Inductor Selection
          2. 8.2.1.2.2 Rectifier Diode Selection
          3. 8.2.1.2.3 Setting the Output Voltage
          4. 8.2.1.2.4 Compensation (COMP)
          5. 8.2.1.2.5 Input Capacitor Selection
          6. 8.2.1.2.6 Output Capacitor Selection
      2. 8.2.2 Application Curves
      3. 8.2.3 Other Application Circuit Examples
  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 Documentation Support
      1. 11.2.1 Related Documentation
    3. 11.3 Receiving Notification of Documentation Updates
    4. 11.4 Support Resources
    5. 11.5 Trademarks
    6. 11.6 Electrostatic Discharge Caution
    7. 11.7 Glossary
  12. 12Mechanical, Packaging, and Orderable Information

Package Options

Mechanical Data (Package|Pins)
Thermal pad, mechanical data (Package|Pins)
Orderable Information

8.2.1.2 Detailed Design Procedure

The first step in the design procedure is to verify that the maximum possible output current of the boost converter supports the specific application requirements. A simple approach is to estimate the converter efficiency by taking the efficiency numbers from the provided efficiency curves or to use a worst case assumption for the expected efficiency (for example: 90%).

Duty cycle (D) is calculated with Equation 1.

Equation 1. TPS61087-Q1 iq1_lvs821.gif

Maximum output current (Iout(max)) is calculated with Equation 2.

Equation 2. TPS61087-Q1 iq2_lvs821.gif

Peak switch current in application (Iswpeak) is calculated with Equation 3.

Equation 3. TPS61087-Q1 iq3_lvs821.gif

The inductor peak-to-peak ripple current (ΔIL) is calculated with Equation 4.

Equation 4. TPS61087-Q1 iq4_lvs821.gif

where

  • VIN is the minimum input voltage.
  • VS is the output voltage.
  • ILIM(min) is the converter switch current limit (minimum switch current limit = 3.2 A).
  • fS is the converter switching frequency (typically 1.2 MHz or 650 kHz).
  • L is the selected inductor value.
  • η is the estimated converter efficiency (use the number from the efficiency plots or 90% as an estimation).

The peak switch current is the steady state peak switch current that the integrated switch, inductor, and external Schottky diode must be able to handle. The calculation must be done for the minimum input voltage where the peak switch current is the highest.