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MMA7260Q
Rev 0, 04/2005
Freescale Semiconductor
Technical Data
Freescale Semiconductor, Inc., 2005. All rights reserved.
1.5g - 6g Three Axis Low-g
Micromachined Accelerometer
The MMA7260Q low cost capacitive micromachined accelerometer
features signal conditioning, a 1-pole low pass filter, temperature
compensation and g-Select which allows for the selection among 4
sensitivities. Zero-g offset full scale span and filter cut-off are factory set and
require no external devices. Includes a Sleep Mode that makes it ideal for
handheld battery powered electronics.
Features
Selectable Sensitivity (1.5g/2g/4g/6g)
Low Current Consumption: 500
A
Sleep Mode: 3
A
Low Voltage Operation: 2.2 V 3.6 V
6mm x 6mm x 1.45mm QFN
High Sensitivity (800 mV/g @1.5 g)
Fast Turn On Time
High Sensitivity (1.5 g)
Integral Signal Conditioning with Low Pass Filter
Robust Design, High Shocks Survivability
Pb-Free Terminations
Environmentally Preferred Package
Low Cost
Typical Applications
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
Gaming : Tilt and Motion Sensing, Event Recorder
Robotics : Motion Sensing
ORDERING INFORMATION
Device Name
Temperture Range
Case No.
Package
MMA7260Q
20 to +85C
1622-01
QFN-16, Tube
MMA7260QR2
20 to +85C
1622-01
QFN-16,Tape & Reel
MMA7260Q
MMA7260Q: XYZ AXIS
ACCELEROMETER
1.5g/2g/4g/6g
16 LEAD
QFN
CASE 1622-01
16
15
14
13
5
6
7
8
1
2
3
4
12
11
10
9
g-Select1
g-Select2
V
DD
V
SS
Sleep
Mode
N/C
N/C
N/C
N/C
N/C
N/C
N/C
N/
C
X
OUT
Y
OUT
Z
OUT
Bottom View
Figure 1. Pin Connections
Top View
MMA7260Q
Sensors
2-2
Freescale Semiconductor
Figure 2. Simplified Accelerometer Functional Block Diagram
ELECTRO STATIC DISCHARGE (ESD)
WARNING: This device is sensitive to electrostatic
discharge.
Although the Freescale accelerometer contains internal
2000 V ESD protection circuitry, extra precaution must be
taken by the user to protect the chip from ESD. A charge of
over 2000 volts can accumulate on the human body or
associated test equipment. A charge of this magnitude can
alter the performance or cause failure of the chip. When
handling the accelerometer, proper ESD precautions should
be followed to avoid exposing the device to discharges which
may be detrimental to its performance.
Table 1. Maximum Ratings
(Maximum ratings are the limits to which the device can be exposed without causing permanent damage.)
Rating
Symbol
Value
Unit
Maximum Acceleration (all axis)
g
max
2000
g
Supply Voltage
V
DD
0.3 to +3.6
V
Drop Test
(1)
1. Dropped onto concrete surface from any axis.
D
drop
1.8
m
Storage Temperature Range
T
stg
40 to +125
C
V
SS
Z
OUT
Y
OUT
X
OUT
g-Select1
g-Select2
Sleep Mode
V
DD
G-Cell
Sensor
Oscillator
Clock
Generator
X-Temp
Comp
Y-Temp
Comp
Z-Temp
Comp
C to V
Converter
Gain
+
Filter
Control Logic
EEPROM Trim Circuits
MMA7260Q
Sensors
Freescale Semiconductor
2-3
Table 2. Operating Characteristics
Unless otherwise noted: 20C < T
A
< 85C, 2.2 V < V
DD
< 3.6 V, Acceleration = 0g, Loaded output
(1)
Characteristic
Symbol
Min
Typ
Max
Unit
Operating Range
(2)
Supply Voltage
(3)
Supply Current
Supply Current at Sleep Mode
(4)
Operating Temperature Range
Acceleration Range, X-Axis, Y-Axis, Z-Axis
g-Select1 & 2: 00
g-Select1 & 2: 10
g-Select1 & 2: 01
g-Select1 & 2: 11
V
DD
I
DD
I
DD
T
A
g
FS
g
FS
g
FS
g
FS
2.2
--
--
20
--
--
--
--
3.3
500
3
--
1.5
2.0
4.0
6.0
3.6
800
10
+85
--
--
--
--
V
A
A
C
g
g
g
g
Output Signal
Zero g (T
A
= 25C, V
DD
= 3.3 V)
(5)
Zero g
Sensitivity (T
A
= 25C, V
DD
= 3.3 V)
1.5g
2g
4g
6g
Sensitivity
Bandwidth Response
XY
Z
V
OFF
V
OFF
, T
A
S
1.5g
S
2g
S
4g
S
6g
S,T
A
f
-3dB
f
-3dB
1.485
--
740
555
277.5
185
--
--
--
1.65
2
800
600
300
200
3
350
150
1.815
--
860
645
322.5
215
--
--
--
V
mg/C
mV/g
mV/g
mV/g
mV/g
%/C
Hz
Hz
Noise
RMS (0.1 Hz 1 kHz)
(4)
Power Spectral Density RMS (0.1 Hz 1 kHz)
(4)
n
RMS
n
PSD
--
--
4.7
350
--
--
mVrms
g/
Control Timing
Power-Up Response Time
(6)
Enable Response Time
(7)
Sensing Element Resonant Frequency
XY
Z
Internal Sampling Frequency
t
RESPONSE
t
ENABLE
f
GCELL
f
GCELL
f
CLK
--
--
--
--
--
1.0
0.5
6.0
3.4
11
2.0
2.0
--
--
--
ms
ms
kHz
kHz
kHz
Output Stage Performance
Full-Scale Output Range (I
OUT
= 30 A)
V
FSO
V
SS
+0.25
--
V
DD
0.25
V
Nonlinearity, X
OUT
, Y
OUT
, Z
OUT
NL
OUT
1.0
--
+1.0
%FSO
Cross-Axis Sensitivity
(8)
V
XY, XZ, YZ
--
--
5.0
%
1. For a loaded output, the measurements are observed after an RC filter consisting of a 1.0 k
resistor and a 0.1 F capacitor to ground.
2. These limits define the range of operation for which the part will meet specification.
3. Within the supply range of 2.2 and 3.6 V, the device operates as a fully calibrated linear accelerometer. Beyond these supply limits the device
may operate as a linear device but is not guaranteed to be in calibration.
4. This value is measured with g-Select in 1.5g mode.
5. The device can measure both + and acceleration. With no input acceleration the output is at midsupply. For positive acceleration the output
will increase above V
DD
/2. For negative acceleration, the output will decrease below V
DD
/2.
6. The response time between 10% of full scale Vdd input voltage and 90% of the final operating output voltage.
7. The response time between 10% of full scale Sleep Mode input voltage and 90% of the final operating output voltage.
8. A measure of the device's ability to reject an acceleration applied 90 from the true axis of sensitivity.
Hz
MMA7260Q
Sensors
2-4
Freescale Semiconductor
PRINCIPLE OF OPERATION
The Freescale accelerometer is a surface-micromachined
integrated-circuit accelerometer.
The device consists of two surface micromachined
capacitive sensing cells (g-cell) and a signal conditioning
ASIC contained in a single integrated circuit package. The
sensing elements are 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
/D). Where A is the area of the
beam,
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 output voltage that is ratiometric and
proportional to acceleration.
Figure 3. Simplified Transducer Physical Model
SPECIAL FEATURES
g-Select
The g-Select feature allows for the selection among 4
sensitivities present in the device. Depending on the logic
input placed on pins 1 and 2, the device internal gain will be
changed allowing it to function with a 1.5g, 2g, 4g, or 6g
sensitivity (
Table 3
). 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. The g-Select1 and g-
Select2 pins can be left unconnected for applications
requiring only a 1.5g sensitivity as the device has an internal
pulldown to keep it at that sensitivity (800mV/g).
Sleep Mode
The 3 axis accelerometer provides a Sleep Mode that is
ideal for battery operated products. When Sleep Mode is
active, the device outputs are turned off, providing significant
reduction of operating current. A low input signal on pin 12
(Sleep Mode) will place the device in this mode and reduce
the current to 3uA typ. For lower power consumption, it is
recommended to set g-Select1 and g-Select2 to 1.5g mode.
By placing a high input signal on pin 12, the device will
resume to normal mode of operation.
Filtering
The 3 axis accelerometer contains onboard single-pole
switched capacitor filters. Because the filter is realized using
switched capacitor techniques, there is no requirement for
external passive components (resistors and capacitors) to set
the cut-off frequency.
Ratiometricity
Ratiometricity simply means the output offset voltage and
sensitivity will scale linearly with 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 supply induced errors
in the analog to digital conversion process.
Acceleration
Table 3. g-Select pin Descriptions
g-Select2
g-Select1
g-Range
Sensitivity
0
0
1.5g
800mV/g
0
1
2g
600mV/g
1
0
4g
300mV/g
1
1
6g
200mV/g
MMA7260Q
Sensors
Freescale Semiconductor
2-5
BASIC CONNECTIONS
Pin Descriptions
Figure 4. Pinout Description
Figure 5. Accelerometer with Recommended
Connection Diagram
PCB Layout
Figure 6Recommended PCB Layout for Interfacing
Accelerometer to Microcontroller
NOTES:
1. Use 0.1 F capacitor on V
DD
to decouple the power
source.
2. Physical coupling distance of the accelerometer to
the microcontroller should be minimal.
3. Flag underneath package is connected to ground.
4. Place a ground plane beneath the accelerometer to
reduce noise, the ground plane should be attached to
all of the open ended terminals shown in
Figure 6
.
5. Use an RC filter with 1.0 k
and 0.1 F on the
outputs of the accelerometer to minimize clock noise
(from the switched capacitor filter circuit).
6. PCB layout of power and ground should not couple
power supply noise.
7. Accelerometer and microcontroller should not be a
high current path.
8. A/D sampling rate and any external power supply
switching frequency should be selected such that
they do not interfere with the internal accelerometer
sampling frequency (11 kHz for the sampling
frequency). This will prevent aliasing errors.
Table 4. Pin Descriptions
Pin No.
Pin Name
Description
1
g-Select1
Logic input pin to select g level.
2
g-Select2
Logic input pin to select g level.
3
V
DD
Power Supply Input
4
V
SS
Power Supply Ground
5 - 7
N/C
No internal connection.
Leave unconnected.
8 - 11
N/C
Unused for factory trim.
Leave unconnected.
12
Sleep Mode
Logic input pin to enable product or
Sleep Mode.
13
Z
OUT
Z direction output voltage.
14
Y
OUT
Y direction output voltage.
15
X
OUT
X direction output voltage.
16
N/C
No internal connection.
Leave unconnected.
Top View
15
16
14 13
12
11
10
1
2
3
4
5
6
7
8
9
g-Select1
NC
NC
NC
g-Select2
V
DD
V
SS
Z
OUT
NC
NC
NC
NC
NC
X
OUT
Y
OUT
Sleep Mode
Sleep Mode
V
DD
V
SS
0.1
F
3
4
V
DD
0.1
F
14
0.1
F
15
12
X
OUT
Y
OUT
1 k
1 k
Logic
Input
2
1
0.1
F
13
Z
OUT
1 k
Logic
Inputs
g-Select2
g-Select1
MMA7260Q
POWER SUPPLY
V
DD
V
SS
Sleep Mode
g-Select1
g-Select2
X
OUT
Y
OUT
Z
OUT
Accel
er
ometer
V
DD
V
SS
V
RH
P0
P1
P2
A/D
IN
A/D
IN
A/D
IN
C
C
C
R
R
R
C
C
C
Mi
cro
c
ontr
o
ll
er
C
C
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