Analog-digital (A-D) converters with a fixed conversion time are subject to errors due to metastability. It is shown that an asynchronous converter in which the conversion time is not bounded is faster, on average, than the synchronous design. Real-time applications require the data to be produced within a fixed time, and failures may occur with the long conversion times that can arise with fully asynchronous converters. For these applications, we show that an internally asynchronous bounded time converter is both faster and more reliable than a synchronous converter.