A -80dB THD, 4Vpp Switched Capacitor Filter for 1.5V Battery-Operated Systems

A fully-differential 5th order SC filter that operates from power supplies as low as 1.5V featuring a ¿80dB THD at 4Vpp output voltage is presented. A measured p-weighted noise of about 120¿Vrms leads to a dynamic range of 81.5dB. This circuit is used as reconstruction filter for a low voltage 14-bit DAC. The THD performance has been achieved thanks to a deep analysis of many distortion mechanisms and to the disclosure of a new distortion cause in sample data filters. The very low voltage operation has been possible by integrating a regulated voltage-multiplier on the same chip. The filter active area is 0.54mm² in a 0.8¿ CMOS technology. Typical power consumption is 0.8mW at 1.5V supply.