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RC Circuit in Mistral DM8148 Reference design for TPS51116 Circuit

Michael Stamler
Prodigy 60 points
Other Parts Discussed in Thread: TPS51116

I have copied the TPS51116 circuit in the Misrtral DM8148 Reference Design and it works well. I am inquiring about a RC circuit that they have that uses a very large, high-power resistor connected to the LL pin. It is R142, a 1.5 ohm 1 Watt resistor in series with a capacitor. It is not clear to me why this resistor is so large as it impacts our tight layout. Thanks

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    TI__Guru**** 191445 points

    I have not seen your reference schematic, but the circuit you describe is probably an RC snubber.  Typically they consist of a capacitor of around 1000 pF and a resistor around 1 ohm.  It is used to reduce ringing and over shoot on the switching node  The energy is dissipated as heat in the resistor.  It must be sized accordingly.  If you can tolerate the additional ringing and overshoot, you may be able to eliminate those two components.