VRS interface with 1/t arming function

摘要

A variable reluctance sensor system (100, 400) for processing a variable reluctance sensor signal (VRS, VRSS) including an arming comparator (108) and an arming circuit (112, 412). The arming comparator compares the variable reluctance sensor signal with an arming threshold (ATH) which decreases proportional to 1/t from a predetermined maximum level (ATH MAX) and asserts an armed signal (ARM) when the variable reluctance sensor signal reaches the arming threshold. The arming threshold may be decreased based on a scaling factor multiplied by 1/t to ensure detection of each pulse of the variable reluctance sensor signal. The arming threshold may decrease to a predetermined minimum level (ATH MIN) sufficiently low to intersect the variable reluctance sensor signal and sufficiently high relative to an expected noise level. The arming threshold is reset (RST) in response to a timing event, such as zero crossing (ZD) of the variable reluctance sensor signal.