TIDUF97 September   2024

 

  1.   1
  2.   Description
  3.   Resources
  4.   Features
  5.   Applications
  6.   6
  7. 1System Description
    1. 1.1 Key System Specifications
  8. 2System Overview
    1. 2.1 Block Diagram
    2. 2.2 Design Considerations
    3. 2.3 Highlighted Products
      1. 2.3.1 TMAG6180-Q1
      2. 2.3.2 MSPM0G3507
      3. 2.3.3 THVD1454
  9. 3System Design Theory
    1. 3.1 Hardware Design
      1. 3.1.1 Angle Sensor Schematic Design
      2. 3.1.2 MSPM0G3507 Schematic Design
      3. 3.1.3 RS485 Transceiver Schematic Design
      4. 3.1.4 Power Supply and Reference Voltage
    2. 3.2 Software Design
      1. 3.2.1 Angle Calculation Timing
      2. 3.2.2 Rotary Angle Calculation
      3. 3.2.3 Rotary Angle Error Sources and Compensation
      4. 3.2.4 Encoder Communication Interface
  10. 4Hardware, Software, Testing Requirements, and Test Results
    1. 4.1 Hardware Requirements
      1. 4.1.1 PCB Overview
      2. 4.1.2 Encoder and JTAG Interface
      3. 4.1.3 Software Requirements
    2. 4.2 Test Setup
    3. 4.3 Test Results
      1. 4.3.1 AMR Sensor Sin and Cos Outputs Measurement
      2. 4.3.2 Static Angle Noise Measurement
      3. 4.3.3 Rotary Angle Accuracy Measurement
        1. 4.3.3.1 Impact of Airgap on Noise, Harmonics, and Total Angle Accuracy
      4. 4.3.4 RS485 Interface and Signal Integrity
  11. 5Design and Documentation Support
    1. 5.1 Design Files
      1. 5.1.1 Schematics
      2. 5.1.2 BOM
      3. 5.1.3 PCB Layout
      4. 5.1.4 Altium Project Files
      5. 5.1.5 Gerber Files
      6. 5.1.6 Assembly Drawings
    2. 5.2 Tools and Software
    3. 5.3 Documentation Support
    4. 5.4 Support Resources
    5. 5.5 Trademarks
  12. 6About the Authors

3.1.3 RS485 Transceiver Schematic Design

TIDA-010947 THVD1454 SchematicFigure 3-3 THVD1454 Schematic

To avoid the switching noise of RS485 transceiver influence the 3.3V power rail, which powers the TMAG6180, a separate 5V supply is used to supply the THVD1454. For reliable operation at all data rates and supply voltages, VCC supply needs to be decoupled with a 1uF ceramic capacitor (C12) located as close to the supply pin as possible. This reference design also uses a level shifter TXU0101 to convert the 5V signal on the THVD1454 R pin to a 3.3V signal to be compatible with MSPM0 GPIO input voltage range.

DE and /RE pins are direction control pins of THVD1454, since THVD1454 works on half-duplex mode. DE and /RE pins are connected together. The pulldown resistor R25 (10kΩ) is added to make sure THVD1454 is working on receive mode by default.

THVD1454 has integrated a 120Ω terminal resistor which is controlled by the TERM pin. The TERM pin is connected to MSPM0 GPIO PA4 to to enable the internal terminal resistor through MSPM0 software.

The 100kΩ pullup resistor R15 and pulldown resistor R22 are connected to A and B separately. These resistors limit the residual clamping current into the transceiver and prevent the transceiver from latching up.