I am trying to understand the theory of RC snubber for synchronous buck converters. Some statements seem to be contradictory to me in the below mentioned application notes:
“The snubber capacitance is designed to block lower frequencies (such as the switching frequency) but appears as a short at the ringing frequency. “ http://www.ti.com/lit/an/slpa010/slpa010.pdf - Page 12
“It is important to notice that only the magnitude of the ringing was affected by the boot-resistor and gate resistor methods. The snubber method also changed the ringing frequency and damped out the ringing waveform” http://www.ti.com/lit/an/slyt465/slyt465.pdf - Page 6
How does the snubber capacitor acts as a short circuit during the ringing frequency ? After all it is the one which decides the new ringing frequency.
Why is Cp (parasitic capacitance) used in the characteristic impedance calculation? The equivalent capacitance should have been considered, which is Cp + Csnubber.