TIDUF82B August   2024  – May 2025 DRV8162 , INA241A , ISOM8710

 

  1.   1
  2.   Description
  3.   Resources
  4.   Features
  5.   Applications
  6.   6
  7. 1System Description
    1. 1.1 Reference Design Overview
    2. 1.2 Key System Specifications
  8. 2System Overview
    1. 2.1 Block Diagram
    2. 2.2 Design Considerations
      1. 2.2.1 Hardware Design
        1. 2.2.1.1 Power Stage Gate Driver
          1. 2.2.1.1.1 Gate Driver
          2. 2.2.1.1.2 Protection Features
          3. 2.2.1.1.3 VGVDD Definition
          4. 2.2.1.1.4 Strap Functions
        2. 2.2.1.2 Power Stage FETs
          1. 2.2.1.2.1 VGS versus RDS(ON)
        3. 2.2.1.3 Phase Current and Voltage Sensing
          1. 2.2.1.3.1 Phase A and Phase B Current Sensing
          2. 2.2.1.3.2 Phase C Current Sensing
          3. 2.2.1.3.3 Voltage Sensing
        4. 2.2.1.4 Host Processor Interface
        5. 2.2.1.5 Gate Drive Shutdown Path
        6. 2.2.1.6 System Diagnostic Measurements
          1. 2.2.1.6.1 Temperature Measurement
        7. 2.2.1.7 System Power Supply
          1. 2.2.1.7.1 12V Rail
          2. 2.2.1.7.2 3.3V Rail
      2. 2.2.2 Software Design
    3. 2.3 Highlighted Products
      1. 2.3.1 DRV8162L
      2. 2.3.2 INA241A
      3. 2.3.3 AMC0106M05
      4. 2.3.4 TPSM861253
      5. 2.3.5 LMR38010
      6. 2.3.6 TMP6131
      7. 2.3.7 ISOM8710
  9. 3Hardware, Software Test Requirements and Test Results
    1. 3.1 Hardware Requirements
      1. 3.1.1 PCB Overview
      2. 3.1.2 Hardware Configuration
        1. 3.1.2.1 Prerequisites
        2. 3.1.2.2 Default Resistor and Jumper Configuration
        3. 3.1.2.3 Connector
          1. 3.1.2.3.1 Host Processor Interface
    2. 3.2 Test Setup
    3. 3.3 Test Results
      1. 3.3.1 Power Management
        1. 3.3.1.1 Power Up
        2. 3.3.1.2 Power Down
      2. 3.3.2 Gate Voltage and Phase Voltage
        1. 3.3.2.1 20 VDC
        2. 3.3.2.2 48 VDC
        3. 3.3.2.3 60 VDC
      3. 3.3.3 Digital PWM and Gate Voltage
      4. 3.3.4 Phase-Current Measurements
      5. 3.3.5 System Test Results
        1. 3.3.5.1 Thermal Analysis
  10. 4Design and Documentation Support
    1. 4.1 Design Files
      1. 4.1.1 Schematics
      2. 4.1.2 BOM
    2. 4.2 Tools and Software
    3. 4.3 Documentation Support
    4. 4.4 Support Resources
    5. 4.5 Trademarks
  11. 5About the Authors
  12. 6Revision History
2.2.1.3.1 Phase A and Phase B Current Sensing

For A and B phase current sensing, as the ADC module of the controller MCU selected for testing the system accepts a maximum input voltage of 3.3V, the measured voltages are scaled into the 0V to 3.3V range. When using a different MCU, a voltage scale of 3.0V can be used, if necessary.

TIDA-010956 Inline Phase Current Sense With INA241 for Phase AFigure 2-3 Inline Phase Current Sense With INA241 for Phase A

This design supports a rated motor current of 85ARMS or 120A at peak. Allowing for some margin, the maximum current sense range is set to 165A. With this specification, a 0.2mΩ, 8W shunt resistor is chosen and an amplifier with a fixed 50 gain is selected.

The in-phase currents measured are bidirectional, so the voltage range calculated is further scaled by 2.

Now, we can use Equation 1 to calculate the voltage range of the amplifier output.

Equation 1. Vscale = Iph ×Rshunt×Gamp×2=165A×0.2mΩ×50×2=3.3V

With the scale set to 3.3V, the voltage reference of the amplifier is also set to make sure that 0A corresponds to the center point of the voltage scale. Figure 2-4 shows the 1.65V bias voltage reference, using a TLV431, that is adopted in this design.

TIDA-010956 TLV431 Schematic From TIDA-010956Figure 2-4 TLV431 Schematic From TIDA-010956

Resistor R18 limits the maximum current flow into the circuit. A 150Ω resistor is chosen. R22 and R24 determines the output voltage of the bias reference circuit. Fix R24 to 10.0kΩ, then R22 can be chosen as 3.3kΩ for the 1.65V bias reference of INA241A.

Make sure that the power dissipation rating of the current sense shunt resistor can sustain the current of the system.

Equation 2. Ploss=IRMS2×Rshunt=165A2×0.2mΩ=5.445W

The 165A is only possible in case of a fault condition. The nominal current rating is 85ARMS, and then the power loss is merely 1.445W. The 8W shunt resistor has enough margin.