MMA8450QT Freescale Semiconductor, MMA8450QT Datasheet - Page 14

• 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

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includes a sensing element and an IC interface able to take the information from the sensing element and to provide a signal to
the external world through an I
interrupt routing scheme to 2 interrupt pins including:
functions. Separate application notes have been provided to help configure the device for each embedded functionality.
5.1
Memory (NVM). On power-up, the trim parameters are read from NVM and applied to the circuitry. In normal use, further
calibration in the end application is not necessary. However, the MMA8450Q allows the user to adjust the Zero-g offset for each
axis after power-up, changing the default offset values. The user offset adjustments are stored in 6 volatile registers. For more
information on device calibration, refer to Freescale application note, AN3916.
5.2
OUT_Z_LSB registers as 2’s complement 12-bit numbers. The most significant 8-bits of each axis are stored in OUT_X (Y,
Z)_MSB, so applications needing only 8-bit results can use these 3 registers and ignore OUT_X(Y, Z)_LSB.
at 12-bits resolution. When the full-scale is set to 8g, the measurement range is -8g to +7.996g, and each LSB corresponds to
1g/256 (3.9 mg) at 12-bits resolution. The resolution is reduced by a factor of 16 if only the 8-bit results are used. For more
information on the data manipulation between data formats and modes, refer to Freescale application note, AN3922. There is a
device driver available that can be used with the Sensor Toolbox demo board (LFSTBEB8450Q) with this application note.
5.3
power savings of the system by allowing the host processor/MCU to go into a sleep mode while the accelerometer independently
stores the data, up to 32 samples per axis. The FIFO can run at all output data rates. There is the option of accessing the full 12-
bit data for accessing only the 8-bit data. When access speed is more important than high resolution the 8-bit data flush is a better
option.
0x13. Fill Buffer Mode collects the first 32 samples and asserts the overflow flag when the buffer is full. It does not collect anymore
data until the buffer is read. This benefits data logging applications where all samples must be collected. The Circular Buffer Mode
allows the buffer to be filled and then new data replaces the oldest sample in the buffer. The most recent 32 samples will be stored
in the buffer. This benefits situations where the processor is waiting for an specific interrupt to signal that the data must be flushed
to analyze the event.
number of samples has filled in the buffer (1 to 32).
Freescale application note, AN3920.
5.4
Mode is enabled, the device has access to all the configurable sampling rates and features as is available in the Normal power
mode. To set the device into Low Power Mode, bit 0 in the System Control Register 2 (0x39) should be set (1) (this bit is cleared
(0) for Normal Power Mode). Low Power Mode reduces the current consumption by internally sleeping longer and averaging the
data less. The Low Power Mode is an additional feature that is independent of the sleep feature.The sleep feature can also be
used to reduce the current consumption by automatically changing to a lower sample rate when no activity is detected.
Power Mode and Auto-Wake/Sleep with specific application examples, refer to Freescale application note, AN3921.
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MMA8450Q
The MMA8450Q is a low-power, digital output 3-axis linear accelerometer packaged in a QFN package. The complete device
All functionality is available in 2g, 4g or 8g dynamic ranges. There are many configuration settings for enabling all the different
The IC interface is factory calibrated for sensitivity and Zero-g offset for each axis. The trim values are stored in Non Volatile
The measured acceleration data is stored in the OUT_X_MSB, OUT_X_LSB, OUT_Y_MSB, OUT_Y_LSB, OUT_Z_MSB, and
When the full-scale is set to 2g, the measurement range is -2g to +1.999g, and each LSB corresponds to 1g/1024 (0.98 mg)
MMA8450Q contains a 32 sample internal FIFO data buffer minimizing traffic across the I
The FIFO contains three modes (Fill Buffer Mode, Circular Buffer Mode, and Disabled) described in the F_SETUP Register
The MMA8450Q FIFO Buffer also has a configurable watermark, allowing the processor to be interrupted after a configurable
For details on the configurations for the FIFO Buffer as well as more specific examples and application benefits, refer to
The MMA8450Q can be set to a low power mode to further reduce the current consumption of the device. When the Low Power
For more information on how to configure the MMA8450Q in Low Power Mode and the power consumption benefits of Low
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8-bit or 12-bit data, high pass filtered data, 8-bit or 12-bit configurable 32 sample FIFO
Low power and Auto-Wake/ Sleep for conservation of current consumption
Single and double pulse detection 1 channel
Motion detection and Freefall 2 channels
Transient detection based on a high pass filter and settable threshold for detecting the change in acceleration above a
threshold
Flexible user configurable portrait landscape detection algorithm addressing many use cases for screen orientation
Functionality
Device Calibration
8-bit or 12-bit Data
Internal FIFO Data Buffer
Low Power Mode
2
C serial interface. There are many embedded features in this accelerometer with a very flexible
2
C bus. The FIFO can also provide
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