TIDUF86A January   2025  – July 2025

 

  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 System Overview
    3. 2.3 Highlighted Products
      1. 2.3.1 LMG3100
      2. 2.3.2 LMR38010
      3. 2.3.3 TMP61
      4. 2.3.4 TPS7B81
      5. 2.3.5 OPA4323
  9. 3System Design Theory
    1. 3.1 Power Stage Design: Three-Phase Inverter
    2. 3.2 LMG3100 GaN-FET Power Stage
    3. 3.3 Power Management
    4. 3.4 Current-Sensing Circuit
    5. 3.5 Overcurrent Protection Circuit
    6. 3.6 Phase Voltage and DC Input Voltage Sensing
    7. 3.7 Power-Stage PCB Temperature Monitor
    8. 3.8 Interface to Host MCU
  10. 4Hardware, Testing Requirements, and Test Results
    1. 4.1 Hardware Requirements
      1. 4.1.1 TIDA-010276 PCB Overview
      2. 4.1.2 TIDA-010276 Jumper Settings
    2. 4.2 Test Setup
    3. 4.3 Test Results
      1. 4.3.1 Power Management and System Power Up and Power Down
      2. 4.3.2 GaN Inverter Switch Node Voltage
      3. 4.3.3 Switch Node Voltage Transient Response
      4. 4.3.4 Impact of PWM Frequency to DC-Bus Voltage Ripple
      5. 4.3.5 Efficiency Measurements
      6. 4.3.6 Thermal Analysis
  11. 5Design and Documentation Support
    1. 5.1 Design Files
      1. 5.1.1 Schematics
      2. 5.1.2 BOM
    2. 5.2 Tools and Software
    3. 5.3 Documentation Support
    4. 5.4 Support Resources
    5. 5.5 Trademarks
  12. 6About the Author
  13. 7Revision History

4.3.6 Thermal Analysis

The thermal analysis of the design is done at 27°C lab temperature with 36VDC input with 20kHz, 40kHz, and 80kHz with the high-power motor driven. The motor is run for about 10 minutes before capturing the temperature. This test is run without a heat sink, an external fan provides air flow at a distance.


TIDA-010276 Thermal Image of TIDA-010276 at 50A Peak, 20kHz PWM

Figure 4-27 Thermal Image of TIDA-010276 at 50A Peak, 20kHz PWM

TIDA-010276 Thermal Image of TIDA-010276 at 50A Peak, 80kHz PWM

Figure 4-29 Thermal Image of TIDA-010276 at 50A Peak, 80kHz PWM

TIDA-010276 Thermal Image of TIDA-010276 at 50A Peak, 40kHz PWM

Figure 4-28 Thermal Image of TIDA-010276 at 50A Peak, 40kHz PWM

Since LMG3100 has exposed dies on top, the case temperature of LMG3100 can be very close to the temperature of the die. The maximum junction temperature is up to 175°C. In this test, some margin is still in the junction temperature.

A small heat sink is used to test the TIDA-010276. Run the motor in 80kHz, 50A peak (27°C lab temperature). Figure 4-30 shows the design with a small heat sink and Figure 4-31 shows the resulting thermal image. If using the TIDA-010276 to run at a higher power, choose a larger heat sink to meet the thermal requirements.


TIDA-010276 TIDA-010276 With Small Heat Sink

Figure 4-30 TIDA-010276 With Small Heat Sink

TIDA-010276 Thermal Image of TIDA-010276 at 50A Peak, 80kHz PWM

Figure 4-31 Thermal Image of TIDA-010276 at 50A Peak, 80kHz PWM