US Patent 7730764 Drop detection device and portable apparatus equipped therewith

There is provided a drop detection device with which a falling state is properly detected even when the device is dropped while itself rotating, for example, and the mistaken detection of a falling state when there is in fact no falling state can be prevented, as well as an portable apparatus equipped with this drop detection device. The portable magnetic disk apparatus comprises an acceleration detector configured to detect acceleration, a calculator configured to calculate acceleration information including a second-order differential value of the acceleration with respect to time detected by the acceleration detector, a threshold setting component configured to set an acceleration threshold ATH with respect to the acceleration for determining whether or not a falling state exists on the basis of the second-order differential value of the acceleration, and a drop detection configured to detect that a falling state exists when the acceleration reaches the acceleration threshold set by the threshold setting component.