SLLA590 May   2022 THVD8000 , THVD8010

 

  1.   Abstract
  2.   Trademarks
  3. 1Introduction
  4. 2THVD80x0 Devices Theory of Operation and Limitations of Use
    1. 2.1 Overview and Similarities between Standard RS-485 Transceivers and THVD80xo Devices
    2. 2.2 Differences between Standard RS-485 Transceivers and THVD8000/8010
    3. 2.3 Standard Approach to Using THVD80xo Devices to Communicate over Power Lines
    4. 2.4 Drawbacks to Standard Approach with Higher Voltage Systems
  5. 3Integration of Line Driver with THVD80x0 Devices to Drive Low Impedance Loads
    1. 3.1 Overcoming Drive Strength Requirement with A Line Driver Amplifier
    2. 3.2 Modification to Typical System Signal Chain Path Through Integration of Line Driver
  6. 4High Voltage Interface and Communication Interface Power Supply
    1. 4.1 Line Driver Output and Input RX signal Protection Circuit
    2. 4.2 High-Voltage Interface
    3. 4.3 Receive Path Optional Bandpass
  7. 5System Level View and Relation to Higher Voltage Implementations
    1. 5.1 Powering the Powerline Communication System
    2. 5.2 System Overview with Selected Test Results
    3. 5.3 Changes to Design for Higher Voltage AC or DC Applications
  8. 6Summary
  9. 7References

Overcoming Drive Strength Requirement with A Line Driver Amplifier

The standard approach to communication over powerlines using the THVD8000 or THVD8010 faces significant obstacles. The first obstacle is the lack of drive strength for loads below 375 Ω; however, the solution to this problem is simple – the addition of a line driver amplifier such as the THS6222. The benefit of this implementation is that larger output voltages can be sustained with more current over lower impedance loads for which a traditional RS-485 driver is specified. The line driver must be able to operate at the modulation frequency chosen and be able to transmit valid data at the specified line to ground impedance of the system, which requires high linearity under heavy line loads. The device doesn’t need to be rated for the AC mains voltage as a protection circuit, transformer, and high voltage capacitor all stand in between the mains voltage and the line driver. The addition of the line driver amplifier like the THS6222 or similar devices can increase the max load from 375 Ω down to between 1 and 5 Ω