SLOA198A September   2014  – December 2021 DRV2665 , DRV2667 , DRV2700 , DRV8662

 

  1.   Trademarks
  2. 1 Boost Converter Basics
  3. 2 DRV8662, DRV2700, DRV2665, and DRV2667 Boost Converter
    1. 2.1 DRV8662, DRV2700, DRV2665, and DRV2667 Boost Converter Efficiency
      1. 2.1.1 Boost Efficiency vs Boost Current
    2. 2.2 DRV8662, DRV2700, DRV2665, and DRV2667 Boost Converter Load Regulation
      1. 2.2.1 Boost Regulation vs Current
  4. 3 Configuring the Boost Converter
  5. 4 Boost Converter Output Voltage
  6. 5 Calculating the Load Current
  7. 6 Selecting an Inductor
    1. 6.1 Inductance Rating
    2. 6.2 Saturation Current Rating
    3. 6.3 Thermal Current Rating
    4. 6.4 Choosing REXT
    5. 6.5 What to Avoid: Using Incorrect Inductor Current Ratings
  8. 7 Calculate the Maximum Boost Current
  9. 8 Output Capacitor Selection
  10. 9 Input Capacitor Selection
  11. 10PCB Layout
    1. 10.1 What to Avoid: Incorrect Inductor Placement
  12. 11Examples
    1. 11.1 Example: Based on the DRV8662EVM
      1. 11.1.1 Configure the Boost Voltage
      2. 11.1.2 Configure the Inductor Current
      3. 11.1.3 Boost Performance Results
    2. 11.2 Example: Based on the DRV2667EVM-CT with 25-nF Piezo Module
      1. 11.2.1 Configure the Boost Voltage
      2. 11.2.2 Configure the Inductor Current
      3. 11.2.3 Boost Performance Results
  13. 12Revision History

7 Calculate the Maximum Boost Current

The maximum support boost current is estimated using Equation 8 and Equation 9.

First calculate the maximum duty cycle of the hysteretic converter. Equation 8 assumes worst-case duty cycle during maximum current.

Equation 8. GUID-0D209D22-0034-4077-8D6F-793DCE6F39C9-low.gif
SymbolDescriptionValueUnit
DBoost Duty Cycle––
Vin_minMinimum VDD–V
ETA (η)Boost Efficiency60%
VboostBoost Voltage–V

If the approximate and the actual measurements do not align perfectly, then you can adjust η, which is the efficiency of the boost converter.

Equation 9. GUID-5CB13013-C0CF-4DE1-B6C0-48C8FB9B08DB-low.gif
SymbolDescriptionValueUnit
Iboost_maxMaximum boost current–A
IlimitBoost current limit (REXT)–A
DBoost duty cycle––

Iboost_max is the maximum boost current the boost can deliver to the amplifier. Compare this current to the current calculated for the load current. The boost current should be higher than the load current.