Freescale Semiconductor
Technical Data
Document Number: MMA2260D
Rev 3, 03/2006
±1.5g
X-Axis Micromachined
Accelerometer
The MMA series of silicon capacitive, micromachined accelerometers feature
signal conditioning, a 2-pole low pass filter and temperature compensation. Zero-
g offset full scale span and filter cut-off are factory set and require no external
devices. A full system self-test capability verifies system functionality.
Features
•
•
•
•
•
•
•
•
Integral Signal Conditioning
High Sensitivity
Linear Output
2nd Order Bessel Filter
Calibrated Self-test
EPROM Parity Check Status
Transducer Hermetically Sealed at Wafer Level for Superior Reliability
Robust Design, High Shock Survivability
MMA2260
MMA2260D: X AXIS SENSITIVITY
MICROMACHINED
ACCELEROMETER
±1.5g
Typical Applications
•
•
•
•
•
•
•
•
Tilt Monitoring
Inclinometers
Appliance Control
Mechanical Bearing Monitoring
Vibration Monitoring and Recording
Sports Diagnostic Devices and Systems
Trailer Brake Controls
Automotive Aftermarket
ORDERING INFORMATION
Device
MMA2260D
MMA2260DR2
MMA2260EG
MMA2260EGR2
Temperature Range
–40 to +105°C
–40 to +105°C
–40 to +105°C
–40 to +105°C
Case No.
475-01
475-01
475-01
475-01
Package
SOIC-16
SOIC-16, Tape & Reel
SOIC-16
SOIC-16, Tape & Reel
D SUFFIX
EG SUFFIX (Pb-FREE)
16-LEAD SOIC
CASE 475-01
V
DD
G-Cell
Sensor
Integrator
Gain
Filter
Temp Comp
and Gain
V
OUT
V
SS
V
SS
V
SS
ST
Self-test
Control Logic &
EPROM Trim Circuits
Oscillator
Clock
Generator
V
OUT
V
SS
STATUS
V
DD
ST
STATUS
1
2
3
4
5
6
7
8
16
15
14
13
12
11
10
9
N/C
N/C
N/C
N/C
N/C
N/C
N/C
N/C
Figure 1. Simplified Accelerometer Functional Block Diagram
Figure 2. Pin Connections
© Freescale Semiconductor, Inc., 2006. All rights reserved.
Table 1. Maximum Ratings
(1)
(Maximum ratings are the limits to which the device can be exposed without causing permanent damage.)
Rating
Unpowered Acceleration (all axes)
Supply Voltage
Drop Test
(1)
Storage Temperature Range
1. Dropped onto concrete surface from any axis.
Symbol
g
upd
V
DD
H
drop
T
stg
Value
2000
-0.3 to +7.0
1.2
-40 to +125
Unit
g
V
m
°C
ELECTRO STATIC DISCHARGE (ESD)
WARNING: This device is sensitive to electrostatic
discharge.
Although the Freescale accelerometers contain internal
2kV 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.
MMA2260D
2
Sensors
Freescale Semiconductor
Table 2. Operating Characteristics
(Unless otherwise noted: –40°C
≤
T
A
≤
+105°C, 4.75
≤
V
DD
≤
5.25, Acceleration = 0g, Loaded output
(1)
)
Characteristic
Operating Range
(2)
Supply Voltage
(3)
Supply Current
Operating Temperature Range
Acceleration Range
Output Signal
Zero g (V
DD
= 5.0 V)
(4)
Sensitivity (T
A
= 25°C, V
DD
= 5.0 V)
(5)
Sensitivity (V
DD
= 5.0 V)
(5)
Bandwidth Response
Nonlinearity
Noise
RMS (0.1 Hz – 1.0 kHz)
Spectral Density (RMS, 0.1 Hz – 1.0 kHz)
(6)
Self-Test
Output Response (V
DD
= 5.0 V)
Input Low
Input High
Input Loading
(7)
Response Time
(8)
Status
(9)(10)
Output Low (I
load
= 100
µA)
Output High (I
load
= –100
µA)
Output Stage Performance
Electrical Saturation Recovery Time
(11)
Full Scale Output Range (I
OUT
= –200
µA)
Capacitive Load Drive
(12)
Output Impedance
Mechanical Characteristics
Transverse Sensitivity
(13)
Symbol
V
DD
I
DD
T
A
g
FS
V
OFF
S
S
f
–3dB
NL
OUT
n
RMS
n
SD
∆V
ST
V
IL
V
IH
I
IN
t
ST
V
OL
V
OH
t
DELAY
V
FSO
C
L
Z
O
V
YX,ZX
Min
4.75
1.1
–40
–
2.3
1140
1110
40
–1.0
–
–
0.3
V
SS
0.7 V
DD
–50
–
–
V
DD
–0.8
–
V
SS
+0.25
–
–
–
Typ
5.00
2.2
–
1.5
2.5
1200
1200
50
–
3.5
350
0.4
–
–
–125
20
–
–
–
–
–
50
–
Max
5.25
3.2
+105
–
2.7
1260
1290
60
+1.0
–
–
0.5
0.3 V
DD
V
DD
–300
25
0.4
–
2.0
V
DD
–0.25
100
–
5.0
Unit
V
mA
°C
g
V
mV/g
mV/g
Hz
% FSO
mVrms
µg/√Hz
V
V
V
µA
ms
V
V
ms
V
pF
Ω
% FSO
1. For a loaded output the measurements are observed after an RC filter consisting of a 1 kΩ resistor and a 0.1
µF
capacitor to ground.
2. These limits define the range of operation for which the part will meet specification.
3. Within the supply range of 4.75 and 5.25 volts, 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. 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 and for negative acceleration the output will decrease below V
DD
/2.
5. Sensitivity limits apply to 0 Hz acceleration.
6. At clock frequency
≅
34 kHz.
7. The digital input pin has an internal pull-down current source to prevent inadvertent self test initiation due to external board level leakages.
8. Time for the output to reach 90% of its final value after a self-test is initiated.
9. The Status pin output is not valid following power-up until at least one rising edge has been applied to the self-test pin. The Status pin is
high whenever the self-test input is high.
10. The Status pin output latches high if the EPROM parity changes to odd. The Status pin can be reset by a rising edge on self-test, unless a
fault condition continues to exist.
11. Time for amplifiers to recover after an acceleration signal causes them to saturate.
12. Preserves phase margin (60°) to guarantee output amplifier stability.
13. A measure of the device's ability to reject an acceleration applied 90° from the true axis of sensitivity.
MMA2260D
Sensors
Freescale Semiconductor
3
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 CMOS signal
conditioning ASIC contained in a single integrated circuit
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 moves
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 (). As
the central mass moves with acceleration, the distance
between the beams change and each capacitor's value will
change, (C = NAε/D). Where A is the area of the facing side
of the beam, e is the dielectric constant, D is the distance
between the beams, and N is the number of beams.
The CMOS 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.
SPECIAL FEATURES
Filtering
Freescale accelerometers contain an onboard 2-pole
switched capacitor filter. 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.
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. A fourth
“plate'' is used in the g-cell as a self-test plate. When the user
applies a logic high input to the self-test pin, a calibrated
potential is applied across the self-test plate and the
moveable plate. The resulting electrostatic force
(Fe =
1
/
2
AV
2
/d
2
) causes the center plate to deflect. The
resultant deflection is measured by the accelerometer's
control ASIC and a proportional output voltage results. This
procedure assures that both the mechanical (g-cell) and
electronic sections of the accelerometer are functioning.
Status
Freescale accelerometers include fault detection circuitry
and a fault latch. The Status pin is an output from the fault
latch, OR'd with self-test, and is set high whenever the
following event occurs:
• Parity of the EPROM bits becomes odd in number.
The fault latch can be reset by a rising edge on the self-test
input pin, unless one (or more) of the fault conditions
continues to exist.
Acceleration
Figure 3. Transducer
Physical Model
Figure 4. Equivalent
Circuit Model
MMA2260D
4
Sensors
Freescale Semiconductor
BASIC CONNECTIONS
Pinout Description
PCB Layout
V
SS
V
SS
V
SS
V
OUT
STATUS
V
DD
ST
.
1
2
3
4
5
6
7
8
16
15
14
13
12
11
10
9
N/C
N/C
N/C
N/C
N/C
N/C
N/C
N/C
STATUS
Accelerometer
ST
V
OUT
V
SS
V
DD
R
1 kΩ
C 0.1
µF
P1
Microcontroller
P0
A/D In
C 0.01
µF
V
SS
C 0.1
µF
V
DD
V
RH
C
0.1
µF
Table 3. Pin Description
Pin No.
1 thru 3
Pin Name
V
SS
Description
Redundant connections to the
internal V
SS
and may be left
unconnected.
Output voltage of the
accelerometer.
Logic output pin to indicate fault.
The power supply ground.
The power supply input.
Logic input pin used to initiate
self-test.
Used for factory trim. Leave
unconnected.
No internal connection. Leave
unconnected.
Power Supply
Figure 6. Recommended PCB Layout for Interfacing
Accelerometer to Microcontroller
NOTES:
1. Use a 0.1
µF
capacitor on V
DD
to decouple the power
source.
2. Physical coupling distance of the accelerometer to the
microcontroller should be minimal.
3. 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.
4. Use an RC filter of 1 kΩ and 0.01
µF
on the output of
the accelerometer to minimize clock noise (from the
switched capacitor filter circuit).
5. PCB layout of power and ground should not couple
power supply noise.
6. Accelerometer and microcontroller should not be a
high current path.
4
5
6
7
8
9 thru 13
14 thru 16
V
OUT
STATUS
V
DD
V
SS
ST
Trim pins
—
V
DD
Logic
Input
8
MMA2260D
ST
V
OUT
5
R1
1 kΩ
STATUS
Output
Signal
6 V
DD
4
7. 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. This will prevent aliasing errors.
C1
0.1
µF
7 V
SS
C2
0.01
µF
Figure 5. SOIC Accelerometer with Recommended
Connection Diagram
MMA2260D
Sensors
Freescale Semiconductor
5
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