AN4191

Doc ID 023815 Rev 1

17/20

As shown in the previous images, the “bad” part shows an incorrect output voltage value

(0.473 V vs. 1.18 V), due to the different MOSFET switching speed and switching times. The

thermal measurements are made at the board startup and no load conditions, using a

thermal camera to detect MOSFET and driver temperatures. Figure 25 and Figure 24 show,

respectively, the images for “good” and “bad” parts.

For the “good” sample, the MOSFET temperature is 35.4 °C, while for the “bad” device its

87.4 °C. A similar temperature increase is detected for the driver: 37.8 °C for the first

●

the longer the MOSFET switching times)

●

Driver temperature increases because of gate drive losses rising.

Unfortunately, full load conditions haven't been reached due to the quick device temperature

increase till maximum rating.

Figure 23.

“Good” part steady-state

waveforms

Figure 24.

“Bad” part steady-state waveforms

AM16429V1

AM16430V1

Figure 25.

“Good” part thermal image

Figure 26.

“Bad” part thermal image

AM16431V1

AM16432V1