To achieve a very high level of integration, ST uses a System-in-Package approach where the ASIC die is stacked on top of the MEMS structure to address applications where small size is a key constraint. The MEMS sensor is composed of a mass which is kept in a continuous oscillating movement so that it reacts to the Coriolis effect when an angular rate is applied to the device. A CMOS ASIC measures the angular rate of the MEMS element relative to the external world and delivers an analog output voltage proportional to that rate.