A 10-bit, 3 ps rms precision time-to-digital converter for diffuse optical tomography measurements

A 10-hit, 771 nW Time-Mode ADC with a 2-Step TDC for Bio-Signal Acquisition

“…The result of the conversion is a digital word representing the time difference and, hence, the sampled analog value, similar to the digital output word in analog-to-digital (AD) conversion. Time-mode systems find more and more applications in the biomedical field, such as biomedical imaging applications [5], diffuse optical tomography measurements [6], and measuring the electrocardiogram R-R interval [7].…”

A hybrid time to digital converter based on digital delay locked loop and analog time to amplitude converter

“…Time to Digital Converters are block circuits used to perform high precision time interval measurements where the time interval is defined by the arrival of two signals, a START signal and a STOP signal. TDCs are widely used in many scientific applications such as Time Correlated Single Photon Counting (TCSPC) [1], Fluorescence Life Time Measurement (FLIM) [2], and Diffuse Optical Tomography (DOT) [3].The simplest TDC can be obtained by connecting a very high frequency clock to a counter to determine the number of periods elapsed between the arrivals of the "Start" signal and the "Stop" signal, this approach is quite simple and allows measurements over a wide dynamic range but the asynchronous nature of the "Start" and "Stop" signals leads to measurement errors. Furthermore, the achieved resolution is limited by the used clock frequency as a result good time resolutions require the use of extremely high frequency rates.…”