US Patent 7623051 Metastability error reduction in signal converter systems

Signal converter systems are provided which reduce degradation of system bit error rate that is caused by metastable conversion errors which generally occur when analog input signals are near reference thresholds Vth of system comparators. When operating correctly, the comparators generate a corresponding converter code when the input signals cross the threshold. Metastability, however, may cause the comparators to fail to generate the corresponding converter code. In system embodiments, logic is provided to sense the absence of comparator decisions at the end of a predetermined decision period. In response to this absence, the system is configured to substitute the corresponding converter code. In another embodiment, the system is configured to substitute the corresponding converter code when it lies outside a predetermined digital code window.