New chances for asynchronous sensor interfaces

Sensor interfaces should provide an output signal that can be read out by a microcontroller. Besides digital output signals also time-modulated signals are highly suited to be read out by microcontrollers. This paper discussed the attractive features of interfaces with time-modulated signals, such as simplicity, a low power consumption and flexibility of the signal processing. As a main drawback, it is mentioned that the quantization noise can be higher than that of a second-order sigma-delta converter. However, with the recent introduction of microcontrollers with a high counter frequency (≫70 MHz), this is no longer true, because the effect quantization noise is far below the level of the thermal noise. As an example, noise characteristics of a practical resistive-sensor system have been discussed.