SLLU368 april   2023

 

  1.   Description
  2.   Features
  3. 1Evaluation Module Overview
    1. 1.1 Kit Contents
  4. 2Operating the EVM
    1. 2.1 Setup
      1. 2.1.1 Single Supply Operation
      2. 2.1.2 Dual Supply Operation
    2. 2.2 Operating the THVD24X2VEVM in Default Setup
    3. 2.3 Operating the THVD24X2VEVM With Modifications
      1. 2.3.1 Single-ended Bus Modification Operational Modes
      2. 2.3.2 Differential Signal Bus Modification Operational Mode
  5. 3Hardware Design Files
    1. 3.1 Schematics
    2. 3.2 PCB Layouts
    3. 3.3 Bill of Materials (BOM)
  6. 4Additional Information
    1. 4.1 Trademarks
  7. 5References

2.3.2 Differential Signal Bus Modification Operational Mode

The differential side of the RS-485 transceiver also has a few possible minor modifications that can be made by the user. There is the option for a termination capacitor and resistor, C12 and R19 for A and B pins and C15 and R24 for Y or Z. These capacitor and termination pads can help model termination and different loading effects on the IC. Another common modification is applying a common-mode voltage through the common-mode jumpers J3 through J5 (RX bus) and J17 through J19 (TX bus), which is routed to the respective bus through common-mode resistors: R17 (A), R21 (B), R22 (Z), and R26 (Y). These resistors are not installed by default. For full common-mode testing, resistors R17, R21, R22, and R26 can be 375 Ω, which is the standard value for RS-485 devices.

Table 2-5 Possible Modifications for Differential Signal Bus

Associated Jumper / Signal

Pad Name

Comment
J3 and J5 / Common Mode on “A” R17 Common Mode Resistor to “A”
J4 and J5 / Common Mode on “B” R21 Common Mode Resistor to “B”
J17 and J18 / Common Mode on “Y” R26 Common Mode Resistor to “Y”
J17 and J19 / Common Mode on “Y” R22 Common Mode Resistor to “Z”
N/A / A and B C12 Termination Capacitor Pad (RX)
N/A / A and B R19 Termination Resistor Pad (RX)
N/A / Y and Z C15 Termination Capacitor Pad (TX)
N/A / Y and Z R24 Termination Resistor Pad (TX)