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

4.1 Line Driver Output and Input RX signal Protection Circuit

When interfacing with higher voltage signals it is best to have robust protection to prevent damage to more sensitive components. The protection circuit connects directly to the line driver and receiving bandpass filter + THVD8000/THVD8010 so the protection circuit must ensure that no signal above the most sensitive components ratings is violated. In the case of the THS6222 and the THVD8000/THVD8010, the THVD80x0 devices are the most sensitive on the line. Luckily, The BOOSTXL-AFE031-DF1 board from TI comes with a perfect protection circuit on its PA output and input pathways for these types of applications and the same architecture can be utilized here. The architecture with diode part numbers shown below in Figure 4-1.

Figure 4-1 Protection Circuit for Line Driver and Transceivers

The power signal ideally should directly connect with the protection circuitry – however the robust protection shown above can help mitigate possible transient signals that could result in system damage without the above protection. There are three main protection concerns that are addressed with the above architecture. The first is that the line driver output is going to be clamped to the line driver’s power source (V_PA) in cases of overvoltage and it will be clamped to ground in cases of undervoltage. The second is very similar to the first in that the RX pathway is also protected – this is done by having the max clamp voltage set to VCC, the THVD8000/8010’s power supply, and the min clamping voltage set to ground. Finally, the third is to have an extra protection TVS diode right off the high voltage interface to add extra protection to both the TX and RX pathways.

Beyond the protection diodes there are the inclusion of LC components. L1 and C1 are a bandpass that should have the THVD8000/8010’s modulated signal within its passband the same can be said about C3 – however if the optional bandpass is included C3 will load that filter. The RC snubber (made of R3 and C4) are there to attenuated high frequency noise – the main concern to address is that the snubber shouldn’t stress the driver at the frequency of interest – which for this case would be the modulation frequency.