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

2 DRV8662, DRV2700, DRV2665, and DRV2667 Boost Converter

The DRV8662, DRV2700, DRV2665, and DRV2667 use a hysteretic boost converter design to generate the high voltage needed to drive Piezos. This section describes the basic operating principle of the hysteretic boost converter.

The hysteretic boost converter uses fairly simple feedback to control the timing and frequency of the switch. The ILIM value in the following figure is the peak current through the inductor every time the switch turns on. Once the peak current is reached, the switch opens. The peak inductor current of the DRV8662, DRV2665, and DRV2667 is set by the resistor on the REXT pin (pin 15).

GUID-134AACAB-AAFA-484F-A821-A2FC7D07C0CE-low.gif

The boost converter only switches when the output voltage (VBST) is below the final target value, meaning that it will only switch when it needs to. Unlike a fixed-frequency boost converter design, the hysteretic boost converter design has a continually varying switching frequency and is load-dependent. Note that the DRV8662, DRV2665, and DRV2667 have forced switching at approximately 37 kHz.