SDAA460 July   2026 ISOUSB211

 

  1.   1
  2.   Abstract
  3.   Trademarks
  4. 1Introduction
  5. 2Power Pins and Internal Rails
  6. 3Available Supply Options
    1. 3.1 Generating the 3.3V Rail (V3P3Vx)
    2. 3.2 Generating the 1.8V Rail (V1P8Vx)
    3. 3.3 Summary of the Four Building Blocks
  7. 4Typical Example Power Configurations
    1. 4.1 Power Configuration for an Isolated Host or Hub (Mixed Internal and External)
    2. 4.2 Power Configuration for Isolating a Self-Powered Peripheral
    3. 4.3 Power Configuration for Isolating a Bus-Powered Peripheral
  8. 5Thermal Considerations When Selecting a Supply Configuration
    1. 5.1 Operation Without External 1.8V Supply
    2. 5.2 Operation With External 1.8V Supply
  9. 6References
  10. 7Revision History

3.2 Generating the 1.8V Rail (V1P8Vx)

  • Internal LDO from VCC: Connect a 2.4V to 5.5V supply to VCCx and let the internal LDO generate V1P8Vx. In the simplest design, VCCx is tied to VBUS of the USB port on the connector side and to the local 3.3V rail on the microcontroller side.
  • External 1.8V supply: Short VCCx and V1P8Vx together and drive both from an external 1.8V supply. This removes the internal 1.8V LDO power dissipation and is the lowest-power option for that side.