ST redesigns MEMS accelerometers
ST’s LIS2HH12 3-axis accelerometer is less sensitive to thermal and mechanical stress from bending of the board/package largely because of two changes to the mechanical structure of the 3-axis accelerometer. In the past the X-Y acceleration was measured in one block in half of the die and the z-axis acceleration was measured in another on the other half of the die.
In practice the center of the die sees the least stress and the Z-dimension is the most sensitive to stress and so the LIS2HH12 splits the XY-measuring structure and places it symmetrically on both sides of the Z-measuring structure. The second structural change is that the Z structure had previously been anchored to the die in two places. The new structure reduces stress by using four anchor points.
The accelerometer has selectable full-scale range of ±2, ±4 or ±8 g and a 16-bit digital output, an integrated temperature sensor, industry-standard I2C and SPI interfaces, a supply-voltage range of 1.7 to 3.6V, and two programmable interrupt generators that help streamline system design. It is housed in a 2mm by 2mm by 1mm package.
With typical zero-g level change versus temperature of ±0.25mg/C, the stability of the LIS2HH12 is a factor of two better than previously announced devices. Also, the rejection versus bending with a typical offset accuracy of ±30mg has improved by 25 percent over the existing solutions.
Engineering samples of the LIS2HH12, in the 2mm by 2mm by 1mm LGA-12 package, are available now. Volume production is expected to start in 1Q14 with unit pricing at $0.90 for quantities of 1,000 pieces.
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