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

8.2.1.2.1 Inductor Selection

The TPS61087-Q1 is designed to work with a wide range of inductors. The main parameter for the inductor selection is the saturation current of the inductor, which must be higher than the peak switch current as calculated in Equation 3 with additional margin to cover for heavy load transients. A more conservative alternative is to choose an inductor with a saturation current at least as high as the maximum switch current limit of 4.8 A. The other important parameter is the inductor DC resistance. As the DC resistance decreases, the efficiency usually increases. It is important to note that the inductor DC resistance is not the only parameter determining the efficiency. Especially for a boost converter where the inductor is the energy storage element, the type and core material of the inductor influences the efficiency as well. At high switching frequencies of 1.2 MHz, inductor core losses, proximity effects, and skin effects become more important. An inductor with a larger form factor usually gives higher efficiency. The efficiency difference between different inductors can vary from 2% to 10%. For the TPS61087-Q1, inductor values from 3 μH to 6 μH are a good choice with a switching frequency of 1.2 MHz, typically 3.3 μH. At 650 kHz, TI recommends inductors from 6 μH to 13 μH, typically 6.8 μH. See Table 3 for inductor selection. Customers must verify and validate selected components for suitability with their application.

TI recommends that the inductor current ripple is below 35% of the average inductor current. Equation 5 can be used to calculate the inductor value (L).

Equation 5. TPS61087-Q1 q1_1_lvs821.gif

where

  • Iout is the maximum output current in the application.

Table 3. Inductor Selection

INDUCTOR VALUE TYPICAL DCR Isat SUPPLIER SIZE (L × W × H mm) COMPONENT CODE
1.2 MHz
4.2 µH 23 mΩ 2.2 A Sumida 5.7 × 5.7 × 3 CDRH5D28
4.7 µH 60 mΩ 2.5 A Wurth Elektronik 5.9 × 6.2 × 3.3 7447785004
5 µH 24 mΩ 2.9 A Coilcraft 7.3 × 7.3 × 4.1 MSS7341
5 µH 23 mΩ 2.4 A Sumida 7 × 7 × 3 CDRH6D28
4.6 µH 38 mΩ 3.15 A Sumida 7.6 × 7.6 × 3 CDR7D28
4.7 µH 33 mΩ 3.9 A Wurth Elektronik 7.3 × 7.3 × 3.2 7447789004
3.3 µH 30 mΩ 4.2 A Wurth Elektronik 7.3 × 7.3 × 3.2 7447789003
650 kHz
10 µH 51 mΩ 2.2 A Wurth Elektronik 7.3 × 7.3 × 3.2 744778910
10 µH 36 mΩ 2.7 A Sumida 8.3 × 8.3 × 3 CDRH8D28
6.8 µH 52 mΩ 2.9 A Sumida 7 × 7 × 2.8 CDRH6D26HPNP
6.2 µH 25 mΩ 3.3 A Sumida 8.3 × 8.3 × 6 CDRH8D58
10 µH 80 mΩ 3.5 A Coilcraft 12.95 × 9.4 × 5.08 DS3316P
10 µH 29 mΩ 4 A Sumida 8.3 × 8.3 × 4.5 CDRH8D43
6.8 µH 55 mΩ 4.1 A Wurth Elektronik 12.7 × 10 × 4.9 74454068