This paper describes time-to-digital converter (TDC) architecture capable of achieving subgate-delay resolution and large detection range at the same time with low power consumption. The proposed TDC is based on a parallel sampling ring oscillator with power gating and dynamic element matching (DEM). Through digital background calibration, the time resolution is determined by the delay difference between successive sampling clocks instead of buffer delay. The ring oscillator is enabled only during the incoming time pulsewidth, leading to low power consumption. A new buffer circuit implementation which enables the ring oscillator to settle to a known position after the ring oscillator stops is proposed. Furthermore, the stop position is latched by cross-coupled inverters to achieve immunity to leakage issues. For each incoming time pulse, the ring oscillator starts oscillation from the buffer before which the previous conversion stops, and thus, it also achieves barrel-shift algorithm for DEM and mitigates buffer mismatch impact. The design is fabricated in 65-nm CMOS technology and occupies a 0.4 mm × 0.3 mm chip area. Measurements of the prototype IC demonstrate a detection range of 98 ns with 6 ps/LSB. It consumes 280 µW from a 1.2 V power supply when operating at a 1-MS/s sampling rate. The measured integral nonlinearity and differential nonlinearity are 0.5 and 0.1 LSB, respectively. Measurements of the prototype IC also demonstrate a single-shot precision of less than 11 ps.
The effects of pressure on the superconducting properties of a Bi-based layered superconductor La2O2Bi3Ag0.6Sn0.4S6, which possesses a four-layer-type conducting layer, have been studied through the electrical resistance and magnetic susceptibility measurements. The crystal structure under pressure was examined using synchrotron x-ray diffraction at SPring-8. In the low-pressure regime, bulk superconductivity with a transition temperature T
c of ∼4.5 K was induced by pressure, which was achieved by in-plane chemical pressure effect owing to the compression of the tetragonal structure. In the high-pressure regime above 6.4 GPa, a structural symmetry lowering was observed, and superconducting transitions with a T
c ∼ 8 K were observed. Our results suggest the possible commonality on the factor essential for T
c in Bi-based superconductors with two-layer-type and four-layer-type conducting layers.
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