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

9.2.2.1 Load Test Without Heat Sink

Figure 31 shows the motor winding current and winding voltage waveforms at a 18-V DC input and a 33-ARMS winding current. The result is tabulated in Table 5. The testing is done at 100% duty cycle. Figure 32 shows the steady state thermal image of the board at the same condition, captured after 10 minutes of continuous running. The maximum FET temperature observed is 87.9°C.

Table 5. Load Test Results at 100% Duty Cycle Without Heat Sink

VDC (V) IDC (A) WINDING CURRENT (RMS) (A) DUTY CYCLE INPUT POWER (W)
18 38 33 100% 680
TIDA-00774 tida-00774-load-test-results-at-18VDC-input-33Arms-winding-current-100-duty-cycle.pngFigure 31. Load Test Results at 18-V DC Input, 33-ARMS Winding Current, 100% Duty Cycle
TIDA-00774 tida-00774-thermal-image-at-18VDC-input-33Arms-winding-current-100-duty-cycle.pngFigure 32. Thermal Image at 18-V DC Input, 33-ARMS Winding Current, 100% Duty Cycle

Figure 33 shows the motor winding current and winding voltage waveforms at a 18-V DC input and a 31.8-ARMS winding current. The result is tabulated in Table 6. The testing is done at 90% duty cycle. Figure 34 shows the steady state thermal image of the board at the same condition, captured after 10 minutes of continuous running. The maximum FET temperature observed is 88.9°C.

Table 6. Load Test Results at 90% Duty Cycle Without Heat Sink

VDC (V) IDC (A) WINDING CURRENT (RMS) (A) DUTY CYCLE INPUT POWER (W)
18 33 31.8 90% 594
TIDA-00774 tida-00774-load-test-results-at-18VDC-input-31.8Arms-winding-current-90-duty-cycle.pngFigure 33. Load Test Results at 18-V DC Input, 31.8-ARMS Winding Current, 90% Duty Cycle
TIDA-00774 tida-00774-thermal-image-at-18VDC-input-31.8Arms-winding-current-90-duty-cycle.pngFigure 34. Thermal Image at 18-V DC Input, 31.8-ARMS Winding Current, 90% Duty Cycle