MMA7330 [NXP]
The MMA73x0L Analog Output Accelerometer Evaluation Boards;
| 型号： | MMA7330 |
| 厂家： | 
NXP |
| 描述： | The MMA73x0L Analog Output Accelerometer Evaluation Boards |
| 文件： | 总6页 (文件大小：183K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
AN3376
Rev 3, 08/2007
rescale Semiconductor
Application Note
The MMA73x0L Analog Output
Accelerometer Evaluation Boards
by: Kimberly Tuck and John Young
Systems and Applications Engineers
Tempe, AZ
INTRODUCTION
This application note describes the MMA7360L (1.5g & 6g),
MMA7340L (3g & 11g) and MMA7330L (4g & 12g) evaluation
boards for Freescale’s multi-axis (X, Y, Z) analog output
LGA-14 packaged 3x5x1 mm3 variable capacitance sensing
accelerometers. This document provides the information
about the evaluation board featuring the accelerometer
devices. The operation of the MMA73x0L accelerometers are
explained including the circuit descriptions and diagrams,
showing the pin-outs with the corresponding functionality of
the features. This document also includes a quick start guide
using the evaluation board.
Table 1. MMA73x0L Accelerometer Characteristics
Part No.
Acceleration
(g)
Sensitivity Zero g Output VDD Supply
IDD Current
(µA)
Rolloff Frequency 0g-Detect Package
(Hz)
(mV/g)
(V)
Voltage
(V)
MMA7360
MMA7340
MMA7330
1.5/6
3/11
4/12
800/206
1.65
3.3
3.3
2.8
400
400
400
400 X,Y
300 Z
Yes
Yes
No
LGA
LGA
LGA
440/117.8
308/83.6
1.65
1.4
400 X,Y
300 Z
400 X,Y
300 Z
The accelerometer evaluation boards are small circuit
DESCRIPTION
boards intended to be used for evaluating the accelerometers
and developing prototypes quickly without requiring a PCB to
be designed to accommodate for the small LGA package. It
also provides a means for understanding the best mounting
position and location of an accelerometer in the product with
the provided board mounting points.
The MMA73x0L accelerometers are surface-
micromachined integrated-circuit accelerometers. These
devices consist of a capacitive sensing g-cell consisting of an
X-Y and a Z cell all within a single package, which is sealed
hermetically at the wafer level using a bulk micromachined
cap wafer. The g-cell is the sensing element of the system
which consists of polysilicon mechanical structures.
Acceleration is detected when a displacement in X, Y, or Z is
detected in the g-cells. The displacement creates a change in
capacitance. The ASIC uses a switched capacitor technique
to measure the g-cell capacitors and the acceleration data is
extracted from a difference in the capacitance. The ASIC
provides signal conditioning and filtering to convert the
capacitance into a high level output voltage which is
ratiometric and proportional to the acceleration. The g-cells
are combined with the signal conditioning ASIC in a single
integrated circuit package.
Some examples of the applications for these
accelerometers are the following:
3D-Gaming: Tilt and Motion Sensing, Event Recorder
HDD MP3 Player: Freefall Detection
Laptop PC: Freefall Detection, Anti-Theft
Cell Phone: Image Stability, Text Scroll, Motion Dialing,
E-Compass
Pedometer: Motion Sensing
PDA: Text Scroll
Navigation and Dead Reckoning: E-Compass Tilt
Compensation
Robotics: Motion Sensing
© Freescale Semiconductor, Inc., 2007. All rights reserved.
supply induced errors in the analog to digital conversion
process.
RATIOMETRICITY
The MMA73x0L has a ratiometric output meaning that the
output offset voltage and the sensitivity scale linearly with the
applied supply voltage. That is, as supply voltage is increased,
the sensitivity and offset increase linearly; as supply voltage
decreases, offset and sensitivity decrease linearly. This is a
key feature when interfacing to a microcontroller or an A/D
converter because it provides system level cancellation of
CIRCUIT DESCRIPTION
Figure 1 and Figure 2 are circuit schematics of the
accelerometer device describing the pin-outs. Figure 3 shows
the output offset values of the device in all six orientations.
This correlates with the polarity of the device shown in
Figure 2.
V
DD
3
4
DIP Switch
V
DD
Self Test
1
2
SW
13 12 11 10
9
8
14
7
N/C
Sleep
6
1
2
3
4
5
3.3 nF
V
DD
3.3 nF
3.3 nF
0.1 μF
ON/OFF V
DD
Switch
Figure 1. Schematic
+Z
+Y
6
8
5
9
4
3
2
1
Top
Side View
Top View
7
14
-X
+X
N/C
Sleep
Bottom
10 11 12 13
-Y
-Z
: Arrow indicates direction of package movement.
Figure 2. Pin-Out and Polarity for MMA73x0L
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Direction of Earth's gravity field.*
Top View
6
8
5
9
4
3
2
1
7
14
Side View
Top
10 11 12 13
@ 0g
X
Y
Z
OUT
@ +1g
@ 0g
Bottom
OUT
OUT
X
Y
Z
@ 0g
@ 0g
@ +1g
OUT
OUT
OUT
Bottom
Top
13 12 11 10
9
5
8
6
X
Y
Z
@ -1g
@ 0g
@ 0g
X
Y
Z
@ +1g
@ 0g
@ 0g
OUT
OUT
OUT
OUT
X
@ 0g
OUT
OUT
Y
@ 0g
@ -1g
14
7
OUT
OUT
Z
OUT
1
2
3
4
X
Y
Z
@ 0g
@ -1g
@ 0g
OUT
OUT
OUT
Figure 3. Static Acceleration Showing Output Offset Values
battery is being used as the power source. SW1 must be set
towards the “on” position for the accelerometer to function.
PIN-OUT DESCRIPTIONS
X, Y, Z Output (Pins 2, 3 and 4)
Sleep Mode Function (Pin 7)
The X, Y and Z output pins provide the analog signal
related to the acceleration of the corresponding axis. The
recommended 3.3 nF capacitor to complete the RC filter at
each accelerometer output is included on the X, Y and Z
outputs in the evaluation board. Each output already has an
internal resistor. The RC filter is required to minimize clock
noise that may be present from the switched capacitor filter
circuit.
This 3 axis accelerometer provides a sleep mode that is
ideal for a battery powered products. Sleep mode is active low.
Therefore, when sleep mode is active, the device outputs are
turned off, providing significant reduction of operating current.
A low input signal on pin 7 will place the device in this mode
and reduce the current to 3μA. For lower power consumption,
it is recommended to set the g-Select to the lower g- mode. By
placing a high input on pin 7, the device will resume the normal
mode of operation. This is selectable on the evaluation board
using either the input/output sleep mode pad or the dip switch
(SW2). Note: the main on/off switch (SW1) must remain on for
sleep mode to be operable.
Power Supply (Pins 5 and 6)
The power is supplied to the control IC through the VDD and
VSS pins. VDD is the positive supply and VSS is the ground.
The control IC operates from a single 3.3 V or 2.8 V power
supply depending on the accelerometer. The MMA7360L and
MMA7340L require a 3.3 V while the MMA7330L requires a
2.8V supply voltage. There is a main on/off switch to conserve
power (SW1).
The evaluation boards have pads for interfacing to the
power source. The pads on the side of the board also provide
a means for connecting to the accelerometer analog output by
soldering a wire from the evaluation board to another
breadboard or system. The main on/off switch enables the
power to the accelerometer and helps preserve battery life if a
Free Fall Functionality (Pin 9)
Pin 9 is used to detect freefall of the accelerometer. The
output from this pin will go high when the outputs from X, Y
and Z become 0-g. This is very useful for various applications
as discussed in some of the previous examples. Pin 9 is a N/C
pin on the MMA7330L and the MMA7340L.
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g-Select Dipswitch Setting (Pin 10)
Table 4. g-Select Pin 10 Descriptions MMA7330L
The g-Select (pin 10) allows for the selection between two
sensitivities present in the device. The dipswitch (SW2) allows
for the choice of two different ranges of acceleration. By
adjusting the dipswitch the device internal gain will be
changed allowing it to function with a 1.5g or 6g sensitivity for
the MMA7360L as shown in Table 2. The corresponding g-
ranges for the MMA7340L and the MMA7330L are shown in
Table 3 and Table 4 respectively. This feature is ideal when a
product has applications requiring different sensitivities for
optimum performance. The sensitivity can be changed at
anytime during the operation of the product. Another option
available is to have the g-Select pin left unconnected for
applications requiring only one sensitivity, as the device has
an internal pull-down to keep it at that sensitivity.
g-Select
g-Range
4g
Sensitivity
308 mV/g
83.6 mV/g
0
1
12g
0g Output = 1.40 V, VDD = 2.80 V
Self Test (Pin 13)
Pin 13 is used for putting the accelerometer into a self test
mode. When this pin is activated using SW3 the actuator in the
g-cell will move and the corresponding Voltage output will
change by +1g. A logic high signal into this input sets the
device in self test mode.The 0g-Detect output can be verified
with the self test. If the board is placed upside down in the
X-Y plane (X = 0g, Y = 0g, Z = -1g). Then the self test can be
activated, causing the z output to change to 0g. When all X, Y
and Z outputs are 0g a high signal is sent to the 0g-Detect
output pin. This verifies the self test and the freefall protection
functionality.
Table 2. g-Select Pin 10 Descriptions MMA7360L
g-Select
g-Range
1.5g
Sensitivity
800 mV/g
206 mV/g
0
1
6g
0g Output = 1.65 V, VDD = 3.30 V
Table 3. g-Select Pin 10 Descriptions MMA7340L
g-Select
g-Range
3g
Sensitivity
440 mV/g
0
1
11g
117.8 mV/g
0g Output = 1.65 V, VDD = 3.30 V
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QUICK START GUIDE: HOW TO USE THE EVALUATION BOARD
1. Connect the external power source to the Evaluation
position. This will activate the device showing X, Y and
Z outputs on the X, Y and Z output pads.
Board. The 3.3V/2.8V input is connected to the + (Vdd)
and Gnd (Vss) using the solder pads.
4. Connect the X, Y and Z outputs to an oscilloscope to
view the outputs, or you can also solder these pads to
a microcontroller or any other measuring device.
2. Turn the side on/off switch into the “on” position as
shown in Figure 4. The on/off switch provides power to
the accelerometer and helps preserve battery life if a
battery is being used as the power source. Therefore
SW1 must be set toward the “on” position for the
accelerometer to function.
5. The evaluation board has pads for interfacing to a
3.3V/2.8V power source or battery. The pads on the
side of the board also provide a means for connecting
the accelerometer analog output by soldering a wire
from the evaluation board to another breadboard or
system.
3. Using a thin pointed tool turn the sleep mode dipswitch
(SW2) to the “on” position as shown in Figure 4, or you
can also power the sleep mode using the solder pad
available. This enables the device. A low signal (0) will
bring the board into sleep mode which puts it in a power
saving mode. In this state there will be no X, Y or Z
outputs on these output solder pads. For normal device
operation though the sleep mode must be in the “on”
6. The g-Select is shown in Figure 4 (SW2) in the lower of
the two possible g-modes. You can also use the solder
pad “G_S” to access and change the g-mode.
7. The “FF” solder pad will output a high signal when the
device has detected that X, Y and Z accelerations are
Self Test Pushbutton
Self Test
X Axis Output
Y Axis Output
Z Axis Output
VSS
Sleep Mode
G-Select
VDD
0g-Detect
g-Select
Sleep Mode
On/Off Switch
Figure 4. Evaluation Board Components
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AN3376
Rev. 3
08/2007
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