STI120NH03L STMicroelectronics, STI120NH03L Datasheet - Page 14

• Manufacturer Part Number: STI120NH03L
• Description: N-channel 30v - 0.005ohm - 60a - To-220 / D2pak / I2pak Stripfet Power Mosfet For Dc-dc Conversion
• Manufacturer: STMicroelectronics

Appendix A
6
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Appendix A
The power losses associated with the FETs in a synchronous buck converter can be
estimated using the equations shown in the table below. The formulas give a good
approximation, for the sake of performance comparison, of how different pairs of devices
affect the converter efficiency. However a very important parameter, the working
temperature, is not considered. The real device behavior is really dependent on how the
heat generated inside the devices is removed to allow for a safer working junction
temperature.
G
G
Figure 18. Buck converter: power losses estimation
The low side (SW2) device requires:
–
–
–
–
–
–
The high side (SW1) device requires:
–
–
–
Very low R
Small Qgls to reduce the gate charge losses
Small Coss to reduce losses due to output capacitance
Small Qrr to reduce losses on SW1 during its turn-on
The Cgd/Cgs ratio lower than Vth/Vgg ratio especially with low drain to source
voltage to avoid the cross conduction phenomenon;
Small Rg and Ls to allow higher gate current peak and to limit the voltage
feedback on the gate
Small Qg to have a faster commutation and to reduce gate charge losses
Low R
DS(on)
DS(on)
to reduce the conduction losses.
to reduce conduction losses
STB120NH03L - STI120NH03L - STP120NH03L