Level-Crossing ADC Sampling With Asynchronous Reset Control

The patent applies preliminary action by performing offset calibration of the comparators before the actual signal conversion process. The calibration phase compensates for comparator offsets in advance, ensuring that during the level-crossing sampling operation, the accumulated offset errors remain within acceptable limits. This preliminary calibration enables the system to maintain high SNDR while operating in low-power level-crossing mode.

The patent implements periodic action by continuously monitoring the accumulated offset errors during level-crossing sampling and periodically updating the calibration values. This periodic recalibration approach allows the system to maintain measurement precision over extended operation periods while keeping the comparators in a low-power state most of the time, thus reducing overall power consumption.

The patent applies dynamics by making the capacitor configuration adaptive rather than static. The system dynamically selects and switches between multiple capacitors based on the input signal frequency and the required hold time. For low-frequency signals requiring long hold times, larger capacitors are activated, while for higher-frequency signals, smaller capacitors suffice. This dynamic adaptation allows the system to achieve the required measurement precision without permanently allocating large capacitor areas.

The patent implements parameter changes by varying the effective capacitance value based on operating conditions. The system changes the capacitor configuration parameters (which capacitors are connected and their combination) according to the signal characteristics and required hold time. This parameter adaptation enables the system to meet accuracy requirements for low-frequency signals with long hold times while minimizing the total capacitor area by not using large capacitors for all operating conditions.

The patent applies segmentation by dividing the continuous signal monitoring into discrete level-crossing events. Instead of continuously sampling at every clock cycle, the system segments the monitoring process to activate the comparators and sampling circuitry only when the input signal crosses predefined threshold levels. This segmentation approach maintains reliable signal detection capability for sparse biological events while dramatically reducing power consumption during periods when no signal crossings occur.

The patent implements this principle by using a calibration mechanism that is activated only when needed rather than continuously. The offset calibration function operates as a short-lived, on-demand process that corrects comparator errors only when accuracy is required, rather than maintaining continuous calibration. This approach ensures reliable signal detection while minimizing the energy cost of calibration operations.