MMA7456LT Freescale Semiconductor, MMA7456LT Datasheet - Page 10

• Manufacturer Part Number: MMA7456LT
• Description: Board Mount Accelerometers 3-AXIS DIGTL 12C&SP1
• Manufacturer: Freescale Semiconductor
• Series: -r

Specifications of MMA7456LT

• Sensing Axis: X, Y, Z
• Acceleration: 2 g, 4 g, 8 g
• Sensitivity: 64 count/g, 32 count/g, 16 count/g
• Package / Case: LGA-14
• Output Type: Digital
• Supply Voltage (max): 3.6 V
• Supply Voltage (min): 2.4 V
• Supply Current: 400 uA
• Maximum Operating Temperature: + 85 C
• Minimum Operating Temperature: - 40 C
• Axis: X, Y, Z
• Acceleration Range: ± 2g, 4g, 8g
• Voltage - Supply: 2.4 V ~ 3.6 V
• Bandwidth: 6kHz - XY, 3.4kHz - Z
• Interface: I²C, SPI
• Mounting Type: Surface Mount
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant

LEVEL DETECTION
When in Level or Pulse detection mode, it is not advisable to read the XYZ measurements because this can conflict with timing.
The interrupts for level and pulse detection are at 600 Hz, while measurement mode is at 125 Hz. It is best to exit the pulse/level
mode before taking a measurement on the XYZ.
Both the Level Detection and Pulse Detection modes can trigger an interrupt. Typically one interrupt is assigned to either pulse
detection or level detection. To detect both at the same time 2 interrupts are required. The level detection mechanism has no
timers associated with it. Once a set acceleration level is reached the interrupt pin will go high and remain high until the interrupt
pin is cleared (See
By default all three axes are enabled and the detection range is 8g only. X and/or Y and/or Z can be disabled. There is a choice
between detecting an Absolute signal or a Positive or Negative only signal on the enabled axes. There is also a choice between
doing a detection for Motion where X or Y or Z > Threshold vs. doing a detection for Freefall where X& Y & Z < Threshold.
$18: Control 1 (Read/Write) Setting the Detection Axes for X, Y and Z
This allows the user to define how many axes to use for detection. All axes are enabled by default. To disable write 1.
XDA: Disable X
YDA: Disable Y
ZDA: Disable Z
$19: Control 2 (Read/Write) Motion Detection (OR Condition) or Freefall Detection (AND Condition
LDPL = 0: Level detection polarity is positive and detecting condition is OR for all 3 axes.
X or Y or Z > Threshold
||X|| or ||Y|| or ||Z|| > Threshold
LDPL = 1: Level detection polarity is negative detecting condition is AND for all 3 axes.
||X|| and ||Y|| and ||Z|| < Threshold
$18: Control 1 (Read/Write): Setting the threshold to be an integer value or an absolute value
This allows the user to set the threshold to be absolute, or to be based on the threshold value as positive or negative.
THOPT = 0 Absolute; THOPT = 1 Positive Negative
$1A: Level Detection Threshold Limit Value (Read/Write)
When an event is detected the interrupt pin (either INT1 or INT2) will go high. The interrupt pin assignment is set up in Register
$18, discussed in the
Source Register $0A.
LDTH[7:0]: Level detection threshold value. If THOPT bit in Detection Control Register is “0”, it is unsigned 7 bits value and
LDTH[7] should be “0”. If THOPT bit is “1”, it is signed 8 bits value.
Sensors
Freescale Semiconductor
X and Y and Z < Threshold
LDTH[7]
DFBW
DFBW
D7
D7
D7
D7
0
--
0
0
0
LDTH[6]
THOPT
THOPT
Assigning, Clearing & Detecting
D6
D6
D6
D6
0
--
0
0
0
Assigning, Clearing & Detecting Interrupts
LDTH[5]
ZDA
ZDA
D5
D5
D5
D5
0
--
0
0
0
LDTH[4]
YDA
YDA
D4
D4
D4
D4
0
--
0
0
0
Interrupts).
LDTH[3]
XDA
XDA
D3
D3
D3
D3
0
--
0
0
0
section. The detection status is monitored by the Detection
INTREG[1]
INTREG[1]
LDTH[2]
DRVO
D2
D2
D2
D2
0
0
0
0
INTREG[0]
INTREG[0]
LDTH[1]
PDPL
D1
D1
D1
D1
0
0
0
0
LDTH[0]
INTPIN
INTPIN
LDPL
D0
D0
D0
D0
)
0
0
0
0
MMA7456L
Reg $1A
Function
Reg $18
Function
Reg $19
Function
Reg $18
Function
Default
Default
Default
Default
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