STD100NH02L ST Microelectronics, STD100NH02L Datasheet - Page 13

• Manufacturer Part Number: STD100NH02L
• Description: N-CHANNEL POWER MOSFET
• Manufacturer: ST Microelectronics

STD100NH02L
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.
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Figure 18. Buck converter: power losses estimation
The low side (SW2) 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;
The high side (SW1) device requires:
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)
Buck converter - power losses estimation
DS(on)
to reduce the conduction losses.
to reduce conduction losses
Buck converter - power losses estimation
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