Freescale MMA6262QR2 ±1.5g dual axis micromachined accelerometer Datasheet

Freescale Semiconductor
Technical Data
Document Number: MMA6260Q
Rev 3, 10/2006
±1.5g Dual Axis
Micromachined Accelerometer
MMA6260Q
MMA6261Q
MMA6262Q
MMA6263Q
The MMA6200 series of low cost capacitive micromachined accelerometers
feature signal conditioning, a 1-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
•
•
•
•
•
•
•
•
•
•
High Sensitivity
Low Noise
Low Power
2.7 V to 3.6 V Operation
6mm x 6mm x 1.98mm QFN
Integral Signal Conditioning with Low Pass Filter
Linear Output
Ratiometric Performance
Self-Test
Robust Design, High Shocks Survivability
MMA6260Q Series: X-Y AXIS
SENSITIVITY MICROMACHINED
ACCELEROMETER
±1.5 g
Bottom View
Typical Applications
•
•
•
•
•
•
•
Tilt Monitoring
Position & Motion Sensing
Freefall Detection
Impact Monitoring
Appliance Control
Vibration Monitoring and Recording
Smart Portable Electronics
16-LEAD
QFN
CASE 1477-02
ORDERING INFORMATION
Package
MMA6260Q
50 Hz
1.2 mA
1477-02
QFN-16, Tube
MMA6260QR2
50 Hz
1.2 mA
1477-02
QFN-16,Tape & Reel
MMA6261Q
300 Hz
1.2 mA
1477-02
QFN-16, Tube
MMA6261QR2
300 Hz
1.2 mA
1477-02
1
12 ST
QFN-16,Tape & Reel
NC
2
11 N/C
QFN-16,Tube
VDD
3
10 N/C
VSS
4
9 N/C
1477-02
MMA6262QR2
150 Hz
2.2 mA
1477-02
QFN-16,Tape & Reel
MMA6263Q
900 Hz
2.2 mA
1477-02
QFN-16, Tube
MMA6263QR2
900 Hz
2.2 mA
1477-02
QFN-16,Tape & Reel
5
6
7
8
N/C
NC
N/C
2.2 mA
14 13
N/C
150 Hz
16 15
N/C
MMA6262Q
Top View
N/C
Case No.
YOUT
IDD
XOUT
Bandwidth
Response
N/C
Device Name
Figure 1. Pin Connections
© Freescale Semiconductor, Inc., 2006. All rights reserved.
G-Cell
Sensor
ST
Self Test
X-Integrator
X-Gain
Control Logic &
EEPROM Trim Circuits
Y-Integrator
X-Filter
Oscillator
Y-Gain
X-Temp
Comp
VDD
XOUT
Clock Generator
Y-Filter
Y-Temp
Comp
YOUT
VSS
Figure 2. Simplified Accelerometer Functional Block Diagram
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)
gmax
±2000
g
Supply Voltage
VDD
–0.3 to +3.6
V
Drop Test(1)
Ddrop
1.2
m
Tstg
–40 to +125
°C
Storage Temperature Range
1. Dropped onto concrete surface from any axis.
ELECTRO STATIC DISCHARGE (ESD)
WARNING: This device is sensitive to electrostatic
discharge.
Although the Freescale accelerometers contain internal
2 kV 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.
MMA6260Q
2
Sensors
Freescale Semiconductor
Table 2. Operating Characteristics
Unless otherwise noted: –20°C < TA < 85°C, 3.0 V < VDD < 3.6 V, Acceleration = 0g, Loaded output (1)
Characteristic
Symbol
Min
Typ
Max
Unit
VDD
2.7
3.3
3.6
V
MMA6260Q, MMA6261Q
IDD
—
1.2
1.5
mA
MMA6262Q, MMA6263Q
IDD
—
2.2
3.0
mA
Operating Temperature Range
TA
–20
—
+85
°C
Acceleration Range
gFS
—
1.5
—
g
Operating Range(2)
Supply Voltage(3)
Supply Current
Output Signal
Zero g (TA = 25°C, VDD = 3.3 V)(4)
Zero g
Sensitivity (TA = 25°C, VDD = 3.3 V)
VOFF
1.485
1.65
1.815
V
VOFF, TA
—
2.0
—
mg/°C
S
740
800
860
mV/g
S, TA
—
0.015
—
%/°C
MMA6260Q
f_3dB
—
50
—
Hz
MMA6261Q
f_3dB
—
300
—
Hz
MMA6262Q
f_3dB
—
150
—
Hz
MMA6263Q
f_3dB
—
900
—
Hz
NLOUT
–1.0
—
+1.0
% FSO
mVrms
Sensitivity
Bandwidth Response
Nonlinearity
Noise
MMA6260Q RMS (0.1 Hz – 1 kHz)
nRMS
—
1.8
—
MMA6261Q RMS (0.1 Hz – 1 kHz)
nRMS
—
3.5
—
MMA6262Q RMS (0.1 Hz – 1 kHz)
nRMS
—
1.3
—
MMA6263Q RMS (0.1 Hz – 1 kHz)
nRMS
—
2.5
—
MMA6260Q, MMA6261Q
nPSD
—
300
—
MMA6262Q, MMA6263Q
nPSD
—
200
—
Power Spectral Density RMS (0.1 Hz – 1 kHz)
ug/√Hz
Self-Test
Output Response
VST
0.9 VDD
—
VDD
V
Input Low
VIL
—
—
0.3 VDD
V
Input High
VIH
0.7 VDD
—
VDD
V
RPO
43
57
71
kΩ
tST
—
2.0
—
ms
VFSO
VSS +0.25
—
VDD –0.25
V
CL
—
—
100
pF
ZO
—
50
300
Ω
Pull-Down Resistance(5)
Response Time(6)
Output Stage Performance
Full-Scale Output Range (IOUT = 200 µA)
Capacitive Load Drive(7)
Output Impedance
Power-Up Response Time
MMA6260Q
tRESPONSE
—
14
—
ms
MMA6261Q
tRESPONSE
—
2.0
—
ms
MMA6262Q
tRESPONSE
—
4.0
—
ms
MMA6263Q
tRESPONSE
—
0.7
—
ms
VZX, YX, ZY
–5.0
—
+5.0
% FSO
Mechanical Characteristics
Transverse Sensitivity(8)
1. For a loaded output, the measurements are observed after an RC filter consisting of a 1.0 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 2.7 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. The device can measure both + and – acceleration. With no input acceleration the output is at midsupply. For positive acceleration the output
will increase above VDD/2. For negative acceleration, the output will decrease below VDD/2.
5. The digital input pin has an internal pull-down resistance to prevent inadvertent self-test initiation due to external board level leakages.
6. Time for the output to reach 90% of its final value after a self-test is initiated.
7. Preserves phase margin (60°) to guarantee output amplifier stability.
8. A measure of the device’s ability to reject an acceleration applied 90° from the true axis of sensitivity.
MMA6260Q
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 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 plates form two back-to-back capacitors
(Figure 4). As the center plate moves with acceleration, the
distance between the plates changes and each capacitor's
value will change, (C = Aε/D). Where A is the area of the
plate, ε is the dielectric constant, and D is the distance
between the plates.
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.
Acceleration
Figure 3. Transducer
Physical Model
SPECIAL FEATURES
Filtering
These Freescale accelerometers contain an onboard
single-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 allowing 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 a logic
high input to the self-test pin is applied, a calibrated potential
is applied across the self-test plate and the moveable plate.
The resulting electrostatic force (Fe = 1/2 AV2/d2) causes the
center plate to deflect. The resultant deflection is measured
by the accelerometer's ASIC and a proportional output
voltage results. This procedure assures both the mechanical
(g-cell) and electronic sections of the accelerometer are
functioning.
Freescale accelerometers include fault detection circuitry
and a fault latch. Parity of the EEPROM bits becomes odd in
number.
Self-test is disabled when EEPROM parity error occurs.
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.
Figure 4. Equivalent
Circuit Model
MMA6260Q
4
Sensors
Freescale Semiconductor
BASIC CONNECTIONS
Pinout Description
PCB Layout
NC
N/C
14 13
1
12 ST
2
11 N/C
5
6
7
8
N/C
9 N/C
N/C
10 N/C
4
N/C
3
VSS
N/C
VDD
VSS
R
1 kΩ
R
1 kΩ
A/D IN
0.1 µF
C
A/D IN
0.1 µF
C
C 0.1 µF
VSS
C 0.1 µF
VDD
VRH
C 0.1 µF
Power Supply
Figure 6. Recommend PCB Layout for Interfacing
Accelerometer to Microcontroller
Pin No.
Pin
Name
1, 5 – 7, 13, 16
N/C
14
YOUT
Output voltage of the accelerometer.
Y Direction.
15
XOUT
Output voltage of the accelerometer.
X Direction.
3
VDD
Power supply input.
4
VSS
The power supply ground.
2, 8 – 11
N/C
Used for factory trim.
Leave unconnected.
Description
No internal connection.
Leave unconnected.
ST
YOUT
VDD
Figure 4. Pinout Description
12
XOUT
Microcontroller
NC
P0
ST
Accelerometer
16 15
YOUT
XOUT
N/C
Top View
NOTES:
1. Use 0.1 µF capacitor on VDD 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 kΩ and 0.1 µF on the outputs
of the accelerometer to minimize clock noise (from the
switched capacitor filter circuit).
Logic input pin used to initiate
self-test.
6. PCB layout of power and ground should not couple
power supply noise.
VDD
7. Accelerometer and microcontroller should not be a
high current path.
MMA6260Q
Series
3
VDD
YOUT
14
0.1 µF
0.1 µF
4
Logic
Input
1 kΩ
12
X Output
Signal
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 (16 kHz for Low IDD and 52 kHz for
Standard IDD for the sampling frequency). This will
prevent aliasing errors.
Y Output
Signal
9. PCB layout should not run traces or vias under the
QFN part. This could lead to ground shorting to the
accelerometer flag.
VSS
XOUT 15
ST
1 kΩ
0.1 µF
Figure 5. Accelerometer with Recommended
Connection Diagram
MMA6260Q
Sensors
Freescale Semiconductor
5
DYNAMIC ACCELERATION
Top View
+Y
16
+X
15
14
13
1
12
2
11
3
10
4
9
5
6
7
–X
8
–Y
16-Pin QFN Package
STATIC ACCELERATION
Top View
Direction of Earth’s gravity field(1)
XOUT @ 0g = 1.65 V
YOUT @ -1g = 0.85 V
XOUT @ -1g = 0.85 V
YOUT @ 0g = 1.65 V
XOUT @ +1g = 2.45 V
YOUT @ 0g = 1.65 V
XOUT @ 0g = 1.65 V
YOUT @ +1g = 2.45 V
1. When positioned as shown, the Earth’s gravity will result in a positive 1g output.
MMA6260Q
6
Sensors
Freescale Semiconductor
MINIMUM RECOMMENDED FOOTPRINT FOR SURFACE MOUNTED APPLICATIONS
Surface mount board layout is a critical portion of the total
design. The footprint for the surface mount packages must be
the correct size to ensure proper solder connection interface
between the board and the package.
With the correct footprint, the packages will self-align when
subjected to a solder reflow process. It is always
recommended to design boards with a solder mask layer to
avoid bridging and shorting between solder pads.
6.0
0.55
4.25
9
8
1.00
5
16
0.50
6.0
13
12
1
Pin 1 ID (non metallic)
4
Flag
Solder areas
Non-Solder areas
MMA6260Q
Sensors
Freescale Semiconductor
7
PACKAGE DIMENSIONS
PAGE 1 OF 3
CASE 1477-02
ISSUE B
16-LEAD QFN
MMA6260Q
8
Sensors
Freescale Semiconductor
PACKAGE DIMENSIONS
PAGE 2 OF 3
CASE 1477-02
ISSUE B
16-LEAD QFN
MMA6260Q
Sensors
Freescale Semiconductor
9
PACKAGE DIMENSIONS
PAGE 3 OF 3
CASE 1477-02
ISSUE B
16-LEAD QFN
MMA6260Q
10
Sensors
Freescale Semiconductor
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MMA6260Q
Rev. 3
10/2006
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