High resolution time-to-digital converter utilizing dual-slope principle

This paper describes the architecture and performance of an analog dual-slope high-resolution time-to-digital converter (TDC). The TDC is used as a basic building block for time interval measurement in an ultrasonic liquid flowmeter. Operation of the TDC with 10ps LSB resolution and 1ms input range has been simulated using transistor models 1.2mum double-metal double-poly CMOS technology. The circuit is based on the interpolation time interval measurement principle. Two separate time digitizers improve the time resolution by interpolating within the clock period. These interpolators are based on dual-slope conversion. Performance concerning linearity, relative error the amount of the stretching factor for different section of design parameters are evaluated.