Table of contents
About this document ....................................................................................................................... 1
Table of contents ............................................................................................................................ 2
1 Systems with CoolSiC™ MOSFETs ............................................................................................. 3
2 Switching frequencies, rise and fall times ................................................................................. 5
2.1 Pulse versus sinus ................................................................................................................................... 5
2.2 Observations on the 100 kHz trapezoidal signal .................................................................................... 8
2.3 Observations on the 100 MHz trapezoidal signal ................................................................................. 11
2.4 Observations with variable rising and falling switching edge ............................................................. 12
2.5 Summary of Fourier considerations ..................................................................................................... 16
3 Transmission line theory ........................................................................................................ 17
3.1 Introduction ........................................................................................................................................... 17
3.2 Line equations ....................................................................................................................................... 18
3.3 Wave propagations on transmission line ............................................................................................. 19
3.4 Special case, low loss lines ................................................................................................................... 21
3.5 Transmission line .................................................................................................................................. 22
3.6 Material properties of lines ................................................................................................................... 23
3.7 Determination of the waveform for line reflections ............................................................................ 23
3.7.1 LATTICE diagram – Example 1 ......................................................................................................... 25
3.7.2 LATTICE diagram – Example 2 ......................................................................................................... 27
3.8 Critical length of lines............................................................................................................................ 29
3.8.1 Critical length of lines for sinusoidal signals ................................................................................... 29
3.8.2 Critical length of lines for trapezoidal (or rectangular) signals ...................................................... 29
4 Circuit basics for impedance matching .................................................................................... 31
4.1 Small signal behavior of transistors ..................................................................................................... 31
4.1.1 Small-signal behavior of bipolar transistors ................................................................................... 31
4.1.2 Small-signal behavior of MOSFET transistors ................................................................................. 32
4.1.3 Push-pull output stage .................................................................................................................... 33
5 Line matching (termination) ................................................................................................... 35
5.1 Driving CMOS circuits via transmission line ......................................................................................... 35
5.1.1 Line termination via series damping ............................................................................................... 35
5.1.2 Line termination via pull-down ....................................................................................................... 36
5.1.3 Line termination via pull-up and pull-down ................................................................................... 37
5.1.4 AC-based line termination ............................................................................................................... 37
5.1.5 Chip interior ...................................................................................................................................... 38
5.2 Transmission line termination for gate drivers .................................................................................... 39
5.2.1 Line termination of single-channel opto drivers via series damping ............................................. 39
5.2.2 Line termination of multi-channel opto drivers via series damping .............................................. 39
5.2.3 Line termination of single-channel CT gate drivers via series damping ........................................ 40
5.2.4 Line termination of multi-channel CT gate drivers via series damping ......................................... 41
6 Summary ............................................................................................................................. 42
7 References and appendices .................................................................................................... 43
7.1 References ............................................................................................................................................. 43
Revision history............................................................................................................................. 44
