A Low-EMI Fully Integrated Switched-Capacitor DC/DC Converter

This paper presents a novel fully integrated step-up dc/dc converter containing circuits to improve electromagnetic emissions. This design utilizes current sources to limit the impulsive current flow into the integrated flying capacitors. This reduces the discontinuous pulse currents normally associated with capacitive converters causing electromagnetic interference (EMI). A variable reference current enables the converter to operate with the lowest possible emissions through the entire operating range and is used to regulate the output voltage. The inclusion of low EMI techniques enables fully integrated power converters to be implemented in systems where noise produced by converters currently restricts or prohibits their use. The proposed 3.2 mW voltage doubler was fabricated in a 0.18 μm CMOS process. With an input voltage range of 1-1.8 V, the converter produces a 1.6-3.3 V output. Experimental results verify the reduction of emissions to meet IEC 61967-4 Class L using current control with a reduction of noise voltage when compared with the circuit without the proposed techniques.