A 0.5-bit step multi-resolution adjustable-input range reconfigurable noise-shaping TDC using multi-step quantizer gated-ring oscillators

A reconfigurable noise-shaping time-to-digital converter (TDC) with adjustable resolution and input range is presented as a solution to nonlinear multi-input readout systems. By varying the frequency of a multi-step quantizer gated-ring oscillator (MSQ-GRO), the resolution and input range are adjusted without affecting the acquisition time. A prototype of a standalone second-order MASH MSQ-GRO-TDC operating over a 34 μs adjustable input range and covering five resolution modes is presented. The MSQ-GRO frequency changes by a factor of approximately \(\sqrt 2\), thus adjusting the resolution in steps of 0.5-bit. With a 12 MHz sampling frequency, the MSQ-GRO-TDC consumes 0.85 mW from a 1.2 V supply and achieves integrated noise of 42.8 and 1.9 ps_rms in 500 and 1 kHz bandwidths, respectively. The measured resolution is 13.3-to-15.3 bits with a sampling signal of 200 kHz in a 5 kHz bandwidth. The input range/resolution optimization allows up to 51% of power saving under the same supply voltage, thus extending the battery lifetime in portable devices. The MSQ-GRO-TDC is used as a data converter for a nonlinear pressure sensor. It achieves a worst-case resolution of 24.5 μbar_rms. It is realized in a standard 0.13 μm CMOS technology and occupies an area of 0.145 mm².