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

2.2 Differences between Standard RS-485 Transceivers and THVD8000/8010

However, the similarities stop at this point. From the single ended side there are two pins that aren’t in most RS-485 Transceivers. The F_SET pin is used to select the carrier frequency of the OOK modulation; a resistor to ground will set the value of the carrier frequency – the tables for the 8000 and 8010 are shown in Table 2-1 and Table 2-2 respectively.

Table 2-1 THVD8000 Modulation Frequency Resistance Chart
RF_SET (K Ω) OOK f0 (kHz)
77 125
50 187.5
19 500
12.5 750
9.3 1000
4.4 2000
1.5 5000
Table 2-2 THVD8010 Modulation Frequency Resistance Chart
RF_SET (K Ω) OOK f0 (kHz)
77 125
50 187.5
31.9 300

For best data integrity have the data rate be at least 10 times lower than the carrier frequency. So, if a 125KHz carrier signal is used the data rate should be no faster than the 12.5 Kbps. Higher carrier frequencies also can enable smaller capacitors and inductors in other parts of the circuit reducing board space needed. Next is the MODE pin – this acts as one enable for the device – a low level means the device is in RX mode while a high signal signifies the device is in TX mode.

On the differential communication side, the differences come down to two items. The first is that polarity is now unimportant as the THVD8000/8010 when receiving data reads active pulse trains as 0’s and no active signals a logic 1 so a polarity flip between A and B will not interfere with communication. The second is that transition times and mode change delays are related to the carrier frequency chosen this along with the extra modulation and demodulation circuitry can cause this device to not reach as high of data rates, but with the benefit of transferring data over power lines.