A high-precision time measurement circuit for pixel detectors using a two-stage timing scheme

Abstract This paper presents a two-stage time measurement architecture that combines coarse timing and fine timing to improve time measurement accuracy. Coarse timing provides a global clock reference through a 10 MHz counter, while fine timing employs a time-to-amplitude converter (TAC) to overcome the limitations of counter accuracy and achieve higher time resolution. The pixel array in the design consists of 128 × 128 pixels, with each pixel unit measuring 40 μm × 45 μm, integrating a low-noise charge-sensitive amplifier (CSA), a comparator, and a TAC. Through this architecture, the proposed solution achieves nanosecond-level time resolution, effectively enhancing the time measurement accuracy of particle collision events. Experimental results indicate that the CSA achieves a charge conversion gain of 101.5 μV/e - , an input dynamic range of 0 to 18 ke - , and a non-linearity error below 1.56%, with an equivalent noise charge (ENC) of approximately 35 e - , ensuring excellent low-noise performance. Furthermore, the time measurement path achieves a time accuracy of approximately 1.33 ns with an effective range of 100 ns, validating its capability for high-precision timing applications. This work provides a viable solution for applying the Topmetal chip to low-energy X-ray polarization time measurement, as well as other high-precision timing applications.