Micropower arcsine circuit for tilt processing

An analogue circuit for producing an arcsine transfer based on a differential pair with source degeneration is presented. The application uses this circuit to post-process an accelerometer signal by normalising with respect to the gravitational acceleration vector to extract inclination. Using diode-connected MOS devices operating in weak inversion, the appropriate trigonometric function, i.e. an arcsine, has been realised to compute tilt. The hardware has been implemented in AMS 0.35 mum 2P4M CMOS technology.