A very low cost, 3-axis, MEMS accelerometer for consumer applications

We report here on a novel 3-axis MEMS accelerometer intended to meet the requirements of a high volume, very low cost sensor in consumer gaming and hand-held applications. In order to balance the performance and cost requirements of such applications, this device achieves 3-axis sensing with a single proof-mass. This accomplishment required significant process, device, and test design novelty. Because of the extreme cost constraints in these markets, this design reexamines the core system trade-offs between single-chip integrated and 2-chip MEMS solutions. A 2-chip solution was chosen in this case. Minimizing package costs lead to the use of chip stacking in an over-molded plastic package. Finally, a sophisticated method of probing the sensor-only die was developed, which allowed the further development of a ¿no-shake¿ sensitivity trim algorithm which does not require mechanical stimulation of the device. Based on the design methodologies described here, a very low cost sensor with superior performance was achieved. The acceleration sensitivity achieved is 300 mV/g with a noise limited resolution of 150 ¿g/¿(Hz). The offset voltage temperature coefficient is less than 0.3 mV/degC.