MMA8450QT Freescale Semiconductor, MMA8450QT Datasheet - Page 16

• Manufacturer Part Number: MMA8450QT
• Description: Board Mount Accelerometers 12bit 3-Axis FIFO HPF PL
• Manufacturer: Freescale Semiconductor

Specifications of MMA8450QT

• Sensing Axis: X, Y, Z
• Acceleration: 2 g, 4 g, 8 g
• Digital Output - Number Of Bits: 12 bit
• Supply Voltage (max): 1.89 V
• Supply Voltage (min): 1.71 V
• Supply Current: 3 uA
• Maximum Operating Temperature: + 85 C
• Minimum Operating Temperature: - 40 C
• Shutdown: Yes
• Sensitivity: 0.976 mg/digit, 1.953 mg/digit, 3.906 mg/digit
• Package / Case: QFN-16
• Output Type: Digital
• Package Type: QFN
• Operating Temperature (min): -40C
• Operating Temperature (max): 85C
• Operating Temperature Classification: Industrial
• Product Depth (mm): 3mm
• Product Height (mm): 1mm
• Product Length (mm): 3mm
• Mounting: Surface Mount
• Pin Count: 16
• Acceleration Range: ± 2g, ± 4g, ± 8g
• No. Of Axes: 3
• Ic Interface Type: I2C, Serial
• Sensor Case Style: QFN
• No. Of Pins: 16
• Supply Voltage Range: 1.71V To 1.89V
• Rohs Compliant: Yes
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

5.8
portrait/landscape) with a large amount of configuration available to provide extreme flexibility to the system designer. The
configurability also allows for the function to work differently for various modes of the end system. For example, the MMA8450Q
Orientation Detection allows up to 10 selectable trip angles for Portrait-to-Landscape, up to10 selectable trip angles for the
transition for Landscape-to-Portrait, and 4 selectable front/back trip angles. Typically the desired hysteresis angle is ±15° from a
45° trip reference point, resulting in |30°| and |60°| trip points. The algorithm is robust enough to handle typical process variation
and uncompensated board mount offset, however, it may result in slight angle variations.
Based on known functionality of linear accelerometers, it is not possible to rotate the device about the Z-axis to detect change in
acceleration at slow angular speeds. The angle at which the image no longer detects the orientation change is referred to as the
“Z-Lock- out angle”. The MMA8450Q Orientation Detection function has eight selectable1g-lockout thresholds; and there are 8
different settings for the Z-Angle lockout.
of orientation changes (i.e., When a person is jogging or due to acceleration changes from being on a bus or in a car). The screen
orientation should not interpret this as a change and the screen should lock in the last known valid position. This added feature,
called the 1g Lockout Threshold, enhances the Orientation Detection function and confirms the reliability of the algorithm for the
system. The MMA8450Q allows for configuring the 1g Lockout Threshold from 1g up to 1.35g (in increments of 0.05g).
configuring the device to support various application use cases, refer to Freescale application note, AN3915.
Landscape.
Figure 7. Illustration of Landscape-to-Portrait Transition
detection as low as 25° from flat. This is user configurable. The default angle is 32° but it can be set as low as 25°.
16
MMA8450Q
The MMA8450Q incorporates an advanced algorithm for orientation detection (ability to detect all 6 orientations including
The MMA8450Q Orientation Detection algorithm confirms the reliability of the function with a configurable Z-lockout angle.
The Orientation Detection function also considers when a device is experiencing acceleration above a set threshold not typical
For further information on the highly configurable embedded Orientation Detection Function, including recommendations for
Figure 7
Figure 9
PORTRAIT
90
°
and
illustrates the Z-angle lockout region. When lifting the device up from the flat position it will be active for orientation
Orientation Detection
Figure 8
Landscape-to-Portrait
Trip Angle = 60
show the definitions of the trip angles going from Landscape-to-Portrait and then also from Portrait-to-
Figure 9. Illustration of Z-Tilt Angle Lockout Transition
°
0° Landscape
PORTRAIT
90
°
NORMAL
DETECTION
REGION
LOCKOUT
REGION
Figure 8. Illustration of Portrait-to-Landscape Transition
Z-LOCK = 32.142°
PORTRAIT
90
0° Landscape
°
Freescale Semiconductor
Portrait-to-Landscape
Trip Angle = 60
0° Landscape
°
Sensors