Figure 4-22 and Figure 4-23 show the thermal tests at 27°C ambient temperature (using Fluke TI40) with the TIDA-010255 power stage running at 7.1 A_RMS and 7.7 A_RMS output phase current at 16-kHz PWM. The top LMG3422R030 case temperature was around 90°C (at 7 A_RMS) and 94.3°C (at 7.7 A_RMS). The six LMG3422R030 devices are quite visible. The LMG3422R030 junction temperature at phase V was measured around 98°C at 7.7 A_RMS through the PWM temperature output with the top-side LMG3422R030, while the bottom-side LMG3422R030 was around 91°C. The bottom LMG3422R030 devices are at a lower temperature, since the thermal PAD and electrically-connected source pins were connected to the large GND plane. The top FET thermal PAD and electrically-connected source pins were connected to the individual switch node with a very small area copper plane to minimize EMI and PCB parasitic output capacitance.

Figure 4-24 outlines the estimated safe operating area (SOA) for TIDA-0100255 without a heat sink assuming natural convection at 320-V DC-link voltage and 8-kHz PWM and 16-kHz PWM. The SOA estimation is based on the measured power losses per Figure 4-19, the LMG3422R030 thermal junction and case temperature measurements with a correction factor to consider the increased R_DS(on) operating at T_j = 125°C.