In a delta-sigma type analog-to-digital converter, an offset varying during operation is removed, and a reduction in time required to generate a stable value after powering on the converter is achieved. A high pass filter is provided with a variable filter coefficient which can vary during operation....http://www.google.de/patents/US6147633?utm_source=gb-gplus-sharePatent US6147633 - Analog-to-digital converter having offset removing function
