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

11.1.2 Configure the Inductor Current

The Piezo load requires approximately 1.88 mA of average current based on the following equation:

Piezo Actuator Current Requirements (Approximate)
Iout_max = 2π × Cactuator × Vboost × ƒin_max Iout_max = 1.884956 mA
Maximum required amplifier current (estimate)
GUID-02DFBA2D-F5EF-4E5C-81E4-0FD24C928699-low.gif Ibat_max = 139.626 mA
Maximum VBAT current

This means that the inductor current limit (REXT) must be sufficiently large to support 1.88 mA.

The DRV8662EVM inductor is already fixed, but from here forward you may choose a different inductor that fits your load requirements. The maximum boost current with 80 Vp boost voltage is 20.3 mA based on the 4.7 µH / 1.8 A Coilcraft inductor selected using the following equations:

Boost Converter Current Capacity (Approximate)
GUID-979B71E0-18CB-42AA-BD6B-6CC5CB7BA3EA-low.gif D = 0.978
Estimated duty cycle at maximum frequency
GUID-06D5C2D1-676E-4B33-8D11-B8C1F4FEE353-low.gif Iboost_max = 20.289 mA
Maximum boost output current estimate
GUID-64995F9E-579B-4302-B59B-D0F1D6575739-low.gif Vboost (V) IOUT (mA)
25 64.92
50 32.46
75 21.64
100 16.23
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