TIDUCL0 January   2017

 

  1. 1 Description
  2. 2 Resources
  3. 3 Features
  4. 4 Applications
  5. 5 Design Images
  6. 6 System Overview
    1. 6.1 System Description
    2. 6.2 Key System Specifications
    3. 6.3 Block Diagram
    4. 6.4 Highlighted Products
      1. 6.4.1 CSD88584Q5DC
      2. 6.4.2 DRV8323
      3. 6.4.3 MSP430F5132
      4. 6.4.4 TPS54061
      5. 6.4.5 LMT87
  7. 7 System Design Theory
    1. 7.1 Power Stage Design—Battery Power Input to the Board
    2. 7.2 Power Stage Design—Three-Phase Inverter
      1. 7.2.1 Design Considerations in Paralleling MOSFETs
        1. 7.2.1.1 Conduction Phase
        2. 7.2.1.2 Switching Phase
      2. 7.2.2 Selecting the Sense Resistor
    3. 7.3 Power Stage Design—DRV8323 Gate Driver
      1. 7.3.1 Gate Drive Features of DRV8323
      2. 7.3.2 Current Shunt Amplifier in DRV8323
      3. 7.3.3 Protection Features in DRV8323
    4. 7.4 Power Stage Design—18-V to 3.3-V DC-DC Converter
    5. 7.5 Power Stage Design —Microcontroller MSP430
    6. 7.6 Power Stage Design—Hall Sensor Interface
    7. 7.7 Temperature Sensing
    8. 7.8 Power Stage Design—External Interface Options and Indications
      1. 7.8.1 Speed Control of Motor
      2. 7.8.2 Direction of Rotation—Digital Input
      3. 7.8.3 LED Indications
      4. 7.8.4 Signal Interface Connector for External Monitoring and Control
  8. 8 Getting Started Hardware and Software
    1. 8.1 Hardware
      1. 8.1.1 Connector Configuration of TIDA-00774
      2. 8.1.2 Programming of MSP430
      3. 8.1.3 Procedure for Board Bring-up and Testing
    2. 8.2 Software
      1. 8.2.1 System Features
      2. 8.2.2 Customizing the Reference Code
        1. 8.2.2.1 PWM_PERIOD
        2. 8.2.2.2 MAX_DUTYCYCLE
        3. 8.2.2.3 MIN_DUTYCYCLE
        4. 8.2.2.4 ACCEL_RATE
        5. 8.2.2.5 Block_Rotor_Duration
      3. 8.2.3 Configuring the DRV8323 Registers (drv8323.c)
      4. 8.2.4 Initializing SPI Communication Between DRV8323 and MSP430 (drv8323.h)
      5. 8.2.5 Running Project in Code Composer Studio (CCS)
  9. 9 Testing and Results
    1. 9.1 Test Setup
    2. 9.2 Test Data
      1. 9.2.1 Functional Tests
        1. 9.2.1.1 3.3-V Power Supply Generated by Step-Down Converter
        2. 9.2.1.2 Gate Drive Voltage Generated by Gate Driver
        3. 9.2.1.3 Dead Time From DRV8323
        4. 9.2.1.4 MOSFET Switching Waveforms
        5. 9.2.1.5 VGS Skew of Parallel FETs During Switching
      2. 9.2.2 Load Test
        1. 9.2.2.1 Load Test Without Heat Sink
        2. 9.2.2.2 Load Test With Heat Sink
        3. 9.2.2.3 Load Test With Heat Sink and Airflow
      3. 9.2.3 Inverter Efficiency Test
      4. 9.2.4 Thermal Rise at Different Power Levels
      5. 9.2.5 Inverter Current Sensing by VDS Monitoring
      6. 9.2.6 Overcurrent and Short-Circuit Protection Test
        1. 9.2.6.1 Cycle-by-Cycle Stall Current Protection by DRV8323 VDS Sensing
        2. 9.2.6.2 Stall Current Latch Protection by DRV8323 VDS Sensing
      7. 9.2.7 Testing for Peak Current Capability
  10. 10Design Files
    1. 10.1 Schematics
    2. 10.2 Bill of Materials
    3. 10.3 PCB Layout Recommendations
      1. 10.3.1 Layout Prints
    4. 10.4 Altium Project
    5. 10.5 Gerber Files
    6. 10.6 Assembly Drawings
  11. 11Software Files
  12. 12Related Documentation
    1. 12.1 Trademarks
  13. 13Terminology
  14. 14About the Author

7.5 Power Stage Design —Microcontroller MSP430

Figure 8 shows the schematic for configuring the MSP430F5132 MCU. The resistor R37 is used to limit the dV/dt at the supply pin of the MSP430F5132. The TIDA-00774 reference design uses 10-μF decoupling capacitors. A 0.1-μF capacitor has been added to obtain the best performance at a high frequency.

The Timer D of the MCU is used for PWM generation. The TD0.1 instance of the timer and the corresponding pins are mapped to the high-side switch PWM. The TD0.2 instance of the timer and the corresponding pins are mapped to the low-side switch PWM. The TIDA-00774 reference design uses unipolar, trapezoidal BLDC control where the high-side switches switching at a high frequency. The low-side switches switch at the electrical frequency of the motor current, which is much lower and the same will switch at a high frequency (complimentary to high-side switch) during the freewheeling period to enable active freewheeling and hence low losses. All the feedback signal voltages including the DC bus voltage, current sense amplifier output, potentiometer voltage for speed control, and temperature sensor output are interfaced to the 10-bit successive approximation (SAR) ADC channels of the MCU. The current sense amplifier output is also connected to the comparator input.

TIDA-00774 tida-00774-schematic-msp430f5132.gifFigure 8. MSP430F5132 Schematic