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

3.2 Modification to Typical System Signal Chain Path Through Integration of Line Driver

The addition of a line driver to the system is straight forward when using the THS6222 and the THVD8000. For all higher voltage interface systems, regardless if they are 110 V or 600 V, can be implemented in either configuration shown in Figure 1-1 and Figure 1-2. Figure 3-1 and Figure 3-2 show how to connect the signal pathways between the THVD8000 and the THS6222.

Figure 3-1 Integration of 2x THVD80x0 Devices with THS6222
Figure 3-2 Integration of 1 THVD80x0 Device with THS6222

Both systems shown, operate in a similar way. For ease of design and less potential issues with integration the approach in Figure 3-2 is best; however, it is possible to use Figure 3-2 to achieve the same end goal with less THVD8000 Transceivers. Not shown, in the previous figures, is the integrated common mode buffer of the THS6222 which DC-couples the inputs to mid-supply of the device.

The differential gain (Av) of the line should set RF1 = RF2; the differential gain is . The standard Av = 10 (RF1 = RF2 = 1240Ω; RG = 274 Ω) is used when integrating the THVD8000 or THVD8010; as the output current drive is what’s most necessary for this application so higher gains than the standard 10V/V are typically unneeded.

Signal chain connections aside, both the THVD8000/8010 and the THS6222 have different control modes that will be switched during operation. For the THVD8000/8010 this is going to be the MODE pin and for the THS6222 it is the BIAS1 and BIAS2 pins. The THVD8000/8010 mode pin lets the device switch between transmit and receive modes while the BIAS pins for the THS6222 set the bias current consumption – where higher bias currents means more power drawn and higher performance with respect to linearity for the operational amplifier. Please see Table 3-1 on system configurations:

Table 3-1 System Configurations
System State BIAS1 (Amp) BIAS2 (Amp) MODE (Transceiver)
Transmit Data (TX) L L H
Receive Data (RX) H H L

This mode table is accurate regardless if you are using the implementation from Figure 3-1 or Figure 3-2

With the basis of adding a line driver discussed - the next step is to talk about how the driver and receive pathways connect with the protection and high voltage interface.