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I'm trying to pick the components to use with this DC/DC Buck-Boost Converter. At page 13, the datasheet says, that for input voltages higher than 4.5 V I need to add an extra 2Ω/1nF RC snubber between SW1 and GND. And my concern is, what resistor size/package should I use? How do I calculate the max current that would go through that network at 1 MHz switching frequency? I know that I could calculate capacitive reactance of that capacitor to know the current, but that seems appropriate only for sine wave voltage, not for a PWM signal with rapidly changing duty cycle.

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The SW1 pin will be Vin + the transient. For 3.3V it doesn't get much more than 4V. So maybe 1V through the cap (momentarily for a few ns, we'll figure the transient square instead of peaky for calcs sake and lasts 10ns with a height of 1V only the AC will go through the cap and reach the resistor).

I don't think I'd worry about the power at all. That pulse is small, way less than 10ns. \$1V^2*2Ω = 2W\$ and \$2W*10ns/1s= 20nW \$ Even with a pulse rate of 1MHz this would be 20nW*1e6 or 20mW, any resistor could handle that and that is worst case upper-bound.

If your really worried about it simulate it, it's really easy with lt spice (if they have the model and they do for 90% of converters, or use LT power cad to generate the spice file) enter image description here

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