Parasitic capacitance calculation of interconnects

[eng_ema]

Hi everybody,

i was working on a layout of a boost converter control
i finished it but now i am trying to calculate the parasitic capacitance of interconnects of power switches
after searching i found that i can do that with software like "Maxwell" or "fastcap"
but i don't now if it possible for MOSFET with large number of fingers

so is there anyone now about this

thanks in advance

 

[Baluncore]

Except for RF MOSFETs in microwave circuits you can ignore parasitic capacitance.

The interconnects will have a few pF at best. Internally the MOSFET will have capacitances measuring hundreds of pF that will be somewhat voltage dependent. Take a look at the internal capacitance specs in a data sheet. A small series resistor, (maybe 10 ohm), is sometimes added in the gate connection to prevent an ultrasonic parasitic oscillation as the MOSFET passes through the transition zone. That effectively isolates the parasitic inductance of the lead.

If you really need to, you can calculate lead capacitance and inductance using parallel wire transmission line approximations. There should be no need to model it.