US Patent 7508177 Method and circuit for reducing regulator output noise

A regulator circuit for reducing the output noise when regulators are switched includes a linear regulator and a switching regulator. The linear regulator generates a first regulator voltage from an input voltage with a first feedback loop. The switching regulator generates a second regulator voltage from the input voltage with a second feedback loop, which is connected to the first feedback loop. A loop control circuit controls the first feedback loop so as to lower the first regulator voltage when the switching regulator is activated.