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參數(shù)資料
| 型號： | MMA7455L |
| 廠商： | 飛思卡爾半導體(中國)有限公司 |
| 英文描述： | Three Axis Low-g Digital Output Accelerometer |
| 中文描述： | 三三軸低g加速度計的數(shù)字輸出 |
| 文件頁數(shù)： | 6/27頁 |
| 文件大?。?/td> | 530K |
| 代理商： | MMA7455L |
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Sensors
6
Freescale Semiconductor
MMA7455L
PRINCIPLE OF OPERATION
The Freescale accelerometer is a surface-micromachined
integrated-circuit accelerometer. The device consists of a
surface micromachined capacitive sensing cell (g-cell) and a
signal conditioning ASIC contained in a single package. The
sensing element is sealed hermetically at the wafer level
using a bulk micromachined cap wafer. The g-cell is a
mechanical structure formed from semiconductor materials
(polysilicon) using semiconductor processes (masking and
etching). It can be modeled as a set of beams attached to a
movable central mass that move between fixed beams. The
movable beams can be deflected from their rest position by
subjecting the system to an acceleration (
Figure 3
).
As the beams attached to the central mass move, the
distance from them to the fixed beams on one side will
increase by the same amount that the distance to the fixed
beams on the other side decreases. The change in distance
is a measure of acceleration. The g-cell beams form two
back-to-back capacitors (
Figure 3
). As the center beam
moves with acceleration, the distance between the beams
changes and each capacitor's value will change, (C = A
ε
/D).
Where A is the area of the beam,
ε
is the dielectric constant,
and D is the distance between the beams.
The ASIC uses switched capacitor techniques to measure
the g-cell capacitors and extract the acceleration data from
the difference between the two capacitors. The ASIC also
signal conditions and filters (switched capacitor) the signal,
providing a high level digital output voltage that is
proportional to acceleration.
Figure 3. Simplified Transducer Physical Model
FEATURES
Self Test
The sensor provides a self test feature that allows the
verification of the mechanical and electrical integrity of the
accelerometer at any time before or after installation. This
feature is critical in applications such as hard disk drive
protection where system integrity must be ensured over the
life of the product. Customers can use self test to verify the
solderability to confirm that the part was mounted to the PCB
correctly. When the self test function is initiated through the
mode control register, accessing the “self test” bit, an
electrostatic force is applied to each axis to cause it to deflect.
The z-axis is trimmed to deflect 1g. This procedure assures
that both the mechanical (g-cell) and electronic sections of
the accelerometer are functioning.
g-Select
The g-Select feature enables the selection between 3
sensitivities for measurement. Depending on the values in
the Mode control register ($16), the MMA7455L’s internal
gain will be changed allowing it to function with a 2g, 4g or 8g
measurement sensitivity. This feature is ideal when a product
has applications requiring two or more sensitivities for
optimum performance and for enabling multiple functions.
The sensitivity can be changed during the operation by
modifying the two GLVL bits located in the mode control
register.
Standby Mode
This digital output 3-axis accelerometer provides a
standby mode that is ideal for battery operated products.
When standby mode is active, the device outputs are turned
off, providing significant reduction of operating current. When
the device is in standby mode the current will be reduced to
2.5 μA typical. In standby mode the device can read and write
to the registers with the I
2
C/SPI available, but no new
measurements can be taken in this mode as all current
consuming parts are off. The mode of the device is controlled
through the mode control register by accessing the two mode
bits as shown in
Table 5
.
Acceleration
$16: Mode control register (Read/Write)
D7
D6
D5
D4
D3
D2
D1
D0
Bit
--
DRPD SPI3W
STON GLVL[1] GLVL[0]
MODE[1] MODE[0]
Function
0
0
0
0
0
0
0
0
Default
Table 4. g-Select Description for 8-Bit Mode
GLVL [1:0]
g-Range
Sensitivity
00
8g
16 LSB/g
10
4g
32 LSB/g
01
2g
64 LSB/g
Table 5. Mode Descriptions
MODE [0:1]
Function
00
Standby Mode
01
Measurement Mode
10
Level Detection Mode
11
Pulse Detection Mode
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相關代理商/技術參數(shù) |
參數(shù)描述 |
|---|---|
| MMA7455L_08 | 制造商:FREESCALE 制造商全稱:Freescale Semiconductor, Inc 功能描述:±2g/±4g/±8g Three Axis Low-g Digital Output Accelerometer |
| MMA7455L_09 | 制造商:FREESCALE 制造商全稱:Freescale Semiconductor, Inc 功能描述:±2g/±4g/±8g Three Axis Low-g Digital Output Accelerometer |
| MMA7455LR1 | 功能描述:加速計 - 板上安裝 3-AXIS DIGITAL 2 4 8G RoHS:否 制造商:Murata 傳感軸:Double 加速:12 g 靈敏度: 封裝 / 箱體: 輸出類型:Analog 數(shù)字輸出 - 位數(shù):11 bit 電源電壓-最大:5.25 V 電源電壓-最小:4.75 V 電源電流:4 mA 最大工作溫度:+ 125 C 最小工作溫度:- 40 C |
| MMA7455LR2 | 功能描述:加速計 - 板上安裝 3-AXIS DIGITAL 2 4 8G RoHS:否 制造商:Murata 傳感軸:Double 加速:12 g 靈敏度: 封裝 / 箱體: 輸出類型:Analog 數(shù)字輸出 - 位數(shù):11 bit 電源電壓-最大:5.25 V 電源電壓-最小:4.75 V 電源電流:4 mA 最大工作溫度:+ 125 C 最小工作溫度:- 40 C |
| MMA7455LT | 功能描述:加速計 - 板上安裝 3-AXIS DIGITAL 2 4 8G RoHS:否 制造商:Murata 傳感軸:Double 加速:12 g 靈敏度: 封裝 / 箱體: 輸出類型:Analog 數(shù)字輸出 - 位數(shù):11 bit 電源電壓-最大:5.25 V 電源電壓-最小:4.75 V 電源電流:4 mA 最大工作溫度:+ 125 C 最小工作溫度:- 40 C |
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