Three-axis accelerometer offers orientation, shake and tap detection

With accelerometer features increasingly being used for user interface purposes in mobile phones, small appliances and gaming, Freescale Semiconductor's latest MEMS-based accelerometer has been specifically designed for handheld portable electronics.

The 3-axis MMA7660FC integrates motion-sensing features such as orientation, shake and tap detection in a 3 x 3 x 0.9mm package. Incorporating automatic wake-up/sleep detection, the device includes various power management features in a bid to extend battery life.

Freescale says that the MMA7660FC has been designed to achieve up to five times longer battery life than current solutions when continuously operating to determine motion. One of the ways it does this is by providing conversion to digital values at a user-configurable output data rate. Designers can choose one of eight sample rates that span from 1 to 120 samples per second. At a one sample per second rate, for example, power consumption of this device in active mode is 47uA (microamps). Meanwhile, system-level power is reduced through an automatic configurable auto wake-up/sleep feature achieved without intervention or polling by the host processor. Power consumption during stand-by mode is 2uA, whilst this device draws just 0.4uA in off mode.

The MMA7660FC is a 1.5g accelerometer that can be configured with custom portrait/landscape trip points for six orientations: left, right, up, down, back, and front. Communication between the MMA7660FC and the main system processor is through an I2C interface.

Capable of surviving shocks up to 10,000g, key applications for the MMA7660FC are thought to include mobile phones, PDAs and digital cameras. Other applications envisaged include shock detection and motion control in PCs and peripherals, activity monitoring in medical and sports applications, and orientation and freefall detection in gaming and toys.

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