Ultra linear dynamic Time-over-Threshold with a simple CR-RC filtering

The Time over Threshold (ToT) method [1] is an effective signal processing method for increasing integrity and decreasing power consumption. However ToT suffers from a poor linearity and its dynamic range is limited. We have proposed a new dynamic Time-over-Threshold (dToT) [2] which converts the pulse height into the time width with a dynamically changing threshold voltage. Its linearity is better than the conventional ToT with a constant threshold voltage, around 3%. This paper describes a new method to achieve further linearity improvement. We propose a combination of a CR-RC filter circuit and a dToT with an RC integrating circuit. In the case that the time constants of the CR-RC filter circuit, the dToT circuit, and the delay time are all the same, the linearity of such a system is much better than ToT (INL:0.1%, theoretically) and the system can still be very simple and the wider dynamic range is achieved. We also analyze its characteristics by changing time-constant parameters and have made a prototype circuit.