Patent ID: 6118188
Filing Date: 2000-09-12
Classification: H03K

Abstract:
A power supply switching circuit for switching power supplies of an integrated circuit, the power supply switching circuit comprising:a comparison element that receives and compares a first voltage signal and a second voltage signal and generates a compare signal, wherein the first voltage signal is derived from a primary voltage provided by a primary power source and the second voltage signal is a secondary voltage provided by a secondary power source;a voltage divider element, having a RC constant, that is coupled to the primary power source and receives the compare signal generated by the comparison element and generates the first voltage signal that is provided to the comparison element; anda bypass element coupled to the voltage divider element and controlled by the compare signal to bypass the RC constant of the voltage divider element and immediately pull the first voltage signal to the primary voltage when, after powering up the primary power source, the first voltage signal becomes greater than the second voltage signal.