AN4150 datasheet(13/20 Pages) STMICROELECTRONICS

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AN4150

Bench tests and simulation results overview

Doc ID 023526 Rev 1

13/20

Bench tests and simulation results overview

By an external DC electronic load, the converter output current is fixed at IOUT = 15 A. Low-

side turn-on and turn-off transients are captured. For a complete comparison in terms of

gate current performance, the following parameters are measured for both devices:

–Igate,max: maximum peak during turn-on;

–Igate,min: minimum value during turn-off;

–

Δt(I>0): time interval duration with Igate > 0;

–

Δt(I<0): time interval duration with Igate < 0;

–Igate,avg(ON): average gate current during turn-on;

–Igate,avg(OFF): average gate current during turn-off;

–Imaint: gate current value when the device is fully ON;

–tf: low-side VGS fall time, measured from 90% to 10% of VGS;

–tr: low-side VGS rise time, measured from 10% to 90% of VGS.

In Figure 10 and Figure 11 the low-side waveforms for device A and device B, respectively,

are reported; the green trace is the LS gate current (1 A/div) whereas the yellow trace is

VGS,LS (5 V/div).

In the above images the turn-on and turn-off transients are clearly visible, with the relative

gate current. During low-side turn-off, the gate current is negative, sunk by the driver to

discharge Power MOSFET intrinsic capacitance. On the other hand, a positive gate current

is needed to provide the right QG (total gate charge) to fully turn on the FET.

The following chart summarizes the parameter measurements performed on device A and

device B:

Figure 10.

Device A gate waveforms

Figure 11.

Device B gate waveforms

AM14947v1

AM14948v1

AN4150 데이터시트(PDF) 13 Page - STMicroelectronics