A metastability-independent time-to-voltage converter

Time-to-voltage converters (TVCs) exploit a digital circuit to convert the time difference between the edges of two digital signals into a single digital pulse whose pulse width is equal to this time difference. This pulse is then used as the control signal that controls the charging duration of a current source-capacitor combination. In all previous TVC designs, the digital circuit consists of a chain of registers, which has a potential metastability hazard. This paper proposes a new architecture of the digital circuit which is independent of this hazard. The circuit was designed in a standard 0.18-mum CMOS process and verified on a Teradyne FLEX tester at a resolution of 39.0625 ps. Experimental results also reveal that the output of the digital circuit is independent of the metastability effect.