Decoupling scheme for mixed voltage integrated circuits

摘要

A decoupling circuit for a mixed voltage integrated circuit chip reduces noise on a high voltage power supply while reducing noise coupling to a low voltage power supply and allowing a thin oxide capacitor dielectric (preferably formed by a process common to the gate insulators of field effect transistors on the chip) to be used for good area-efficiency of the filter capacitors. A series connection of capacitors to ground is used in combination with a resistive charging connection connected to a low voltage power supply to prevent a voltage exceeding a breakdown voltage of the thin oxide being applied to the capacitors. The resistive charging connection in combination with a capacitive voltage divider action of the series connected capacitances provides improved noise attenuation coupled to the low voltage supply.