Data Sheet

MMA1270KEG
Rev 0, 11/2009
Freescale Semiconductor
Technical Data
Low G
Micromachined Accelerometer
MMA1270KEG
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.
MMA1270KEG: Z-AXIS SENSITIVITY
MICROMACHINED
ACCELEROMETER
±2.5g
Features
•
•
•
•
•
•
•
•
Integral Signal Conditioning
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
Qualified AEC-Q100, Rev. F Grade 2 (-40°C/ +105°C)
Typical Applications
•
•
•
•
•
•
•
Vibration Monitoring and Recording
Appliance Control
Mechanical Bearing Monitoring
Computer Hard Drive Protection
Computer Mouse and Joysticks
Virtual Reality Input Devices
Sports Diagnostic Devices and Systems
KEG SUFFIX (Pb-FREE)
16-LEAD SOIC
CASE 475-01
ORDERING INFORMATION
Device Name
Temperature Range
Case No.
Package
MMA1270EG
–40° to 105°C
475-01
SOIC-16
MMA1270EGR2
–40° to 105°C
475-01
SOIC-16, Tape & Reel
MMA1270KEG*
–40° to 105°C
475-01
SOIC-16
MMA1270KEGR2*
–40° to 105°C
475-01
SOIC-16, Tape & Reel
*Part number sourced from a different facility.
VDD
G-Cell
Sensor
Integrator
Self-test
Control Logic &
EPROM Trim Circuits
ST
Gain
Filter
Temp Comp
and Gain
Oscillator
Clock
Generator
VOUT
VSS
VSS
VSS
VSS
VOUT
STATUS
VDD
VSS
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
Figure 1. Simplified Accelerometer Functional Block Diagram
© Freescale Semiconductor, Inc., 2009. All rights reserved.
Figure 2. Pin Connections
Table 1. Maximum Ratings
(Maximum ratings are the limits to which the device can be exposed without causing permanent damage.)
Rating
Symbol
Value
Unit
Powered Acceleration (all axes)
Gpd
1500
g
Unpowered Acceleration (all axes)
Gupd
2000
g
Supply Voltage
VDD
–0.3 to +7.0
V
Drop Test (1)
Hdrop
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
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.
MMA1270KEG
2
Sensors
Freescale Semiconductor
Table 2. Operating Characteristics
(Unless otherwise noted: –40°C ≤ TA ≤ +105°C, 4.75 ≤ VDD ≤ 5.25, Acceleration = 0g, Loaded output.(1))
Characteristic
Symbol
Min
Typ
Max
Unit
VDD
IDD
TA
gFS
4.75
1.1
– 40
—
5.00
2.1
—
2.5
5.25
3.0
+105
—
V
mA
°C
g
VOFF
VOFF
S
S
f -3dB
NLOUT
2.25
2.2
712.5
693.8
40
– 1.0
2.5
2.5
750
750
50
—
2.75
2.8
787.5
806.3
60
+1.0
V
V
mV/g
mV/g
Hz
% FSO
Noise
RMS (0.1 Hz – 1.0 kHz)
Spectral Density (RMS, 0.1 Hz – 1.0 KHz)(6)
nRMS
nSD
—
—
3.5
700
6.5
—
mVrms
μg/√Hz
Self-Test
Output Response (VDD = 5.0 V)
Input Low
Input High
Input Loading(7)
Response Time(8)
ΔVST
VIL
VIH
IIN
tST
0.9
VSS
0.7 VDD
– 300
—
1.25
—
—
– 125
10
1.6
0.3 VDD
VDD
– 50
25
V
V
V
μA
ms
Status(9), (10)
Output Low (Iload = 100 μA)
Output High (Iload = 100 μA)
VOL
VOH
—
VDD – 0.8
—
—
0.4
—
V
V
Output Stage Performance
Electrical Saturation Recovery Time(11)
Full Scale Output Range (IOUT = 200 μA)
Capacitive Load Drive(12)
Output Impedance
tDELAY
VFSO
CL
ZO
—
VSS +0.25
—
—
—
—
—
50
2.0
VDD – 0.25
100
—
ms
V
pF
Ω
Mechanical Characteristics
Transverse Sensitivity(13)
VXZ,YZ
—
—
5.0
% FSO
Operating Range(2)
Supply Voltage(3)
Supply Current
Operating Temperature Range
Acceleration Range
Output Signal
Zero g (TA = 25°C, VDD = 5.0 V)(4)
Zero g (VDD = 5.0 V)
Sensitivity (TA = 25°C, VDD = 5.0 V)(5)
Sensitivity (VDD = 5.0 V)
Bandwidth Response
Nonlinearity
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 VDD/2 and for negative acceleration the output will decrease below VDD/2.
5. The device is claibrated at 2g. Sensitivity limits apply to 0 Hz acceleration.
6. At clock frequency ≅ 70 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 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.
MMA1270KEG
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 two
stationary plates with a moveable plate in-between. The
center plate can be deflected from its rest position by
subjecting the system to an acceleration (Figure 3).
When the center plate deflects, the distance from it to one
fixed plate will increase by the same amount that the distance
to the other plate 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 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.
Acceleration
Figure 3. Transducer
Physical Model
SPECIAL FEATURES
Filtering
The Freescale accelerometers contain an onboard 2-pole
switched capacitor filter. A Bessel implementation is used
because it provides a maximally flat delay response (linear
phase) thus preserving pulse shape integrity. 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. This
feature is critical in applications such as automotive airbag
systems where system integrity must be ensured over the life
of the vehicle. A fourth “plate'' is used in the g-cell as a selftest plate. When the user applies a logic high input to the selftest pin, 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
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 selftest input pin, unless one (or more) of the fault conditions
continues to exist.
Figure 4. Equivalent
Circuit Model
MMA1270KEG
4
Sensors
Freescale Semiconductor
BASIC CONNECTIONS
PCB Layout
16
15
14
13
12
11
10
9
1
2
3
4
5
6
7
8
N/C
N/C
N/C
N/C
N/C
N/C
N/C
N/C
STATUS
P1
ST
P0
Accelerometer
VSS
VSS
VSS
VOUT
STATUS
VDD
VSS
ST
VOUT
VSS
VDD
R
1 kΩ
A/D In
C
0.1 μF
C 0.1 μF
Microcontroller
Pinout Description
VSS
C 0.1 μF
VDD
VRH
C 0.1 μF
Table 3. Pin Descriptions
Power Supply
Pin No.
Pin Name
Description
1 thru 3
VSS
Redundant connections to the internal
VSS and may be left unconnected.
4
VOUT
5
STATUS
6
VDD
The power supply input.
7
VSS
The power supply ground.
8
ST
Logic input pin used to initiate self-test.
9 thru 13
Trim pins
14 thru 16
—
Figure 6. Recommended PCB Layout for Interfacing
Accelerometer to Microcontroller
Output voltage of the accelerometer.
Logic output pin used to indicate fault.
NOTES:
1. Use a 0.1 μF capacitor on VDD to decouple the power
source.
2. Physical coupling distance of the accelerometer to the
microcontroller should be minimal.
Used for factory trim.
Leave unconnected.
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 0.1 μF on the output of the
accelerometer to minimize clock noise (from the
switched capacitor filter circuit).
No internal connection.
Leave unconnected.
5. PCB layout of power and ground should not couple
power supply noise.
VDD
8
LOGIC
INPUT
C1
0.1 μF
6
1
2
3
MMA1270KEG
5
ST
VDD
VSS
VSS
VSS
7 VSS
VOUT
4
STATUS
R1
1 kΩ
OUTPUT
SIGNAL
C2
0.1 μF
6. Accelerometer and microcontroller should not be a
high current path.
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.
Figure 5. SOIC Accelerometer with Recommended
Connection Diagram
MMA1270KEG
Sensors
Freescale Semiconductor
5
ACCELERATION SENSING DIRECTIONS
DYNAMIC ACCELERATION
VSS
VSS
VSS
VOUT
STATUS
VDD
VSS
ST
+g
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
16-Pin SOIC Package
N/C pins are recommended to be left FLOATING
–g
STATIC ACCELERATION
Direction of Earth's gravity field(1)
+1g
VOUT = 3.25 V
0g
0g
VOUT = 2.50 V
VOUT = 2.50 V
–1g
VOUT = 1.75 V
1. When positioned as shown, the Earth's gravity will result in a positive 1g output
MMA1270KEG
6
Sensors
Freescale Semiconductor
PACKAGE DIMENSIONS
PAGE 1 OF 2
CASE 475-01
ISSUE C
16-LEAD SOIC
MMA1270KEG
Sensors
Freescale Semiconductor
7
PACKAGE DIMENSIONS
PAGE 2 OF 2
CASE 475-01
ISSUE C
16-LEAD SOIC
MMA1270KEG
8
Sensors
Freescale Semiconductor
How to Reach Us:
Home Page:
www.freescale.com
Web Support:
http://www.freescale.com/support
USA/Europe or Locations Not Listed:
Freescale Semiconductor, Inc.
Technical Information Center, EL516
2100 East Elliot Road
Tempe, Arizona 85284
1-800-521-6274 or +1-480-768-2130
www.freescale.com/support
Europe, Middle East, and Africa:
Freescale Halbleiter Deutschland GmbH
Technical Information Center
Schatzbogen 7
81829 Muenchen, Germany
+44 1296 380 456 (English)
+46 8 52200080 (English)
+49 89 92103 559 (German)
+33 1 69 35 48 48 (French)
www.freescale.com/support
Japan:
Freescale Semiconductor Japan Ltd.
Headquarters
ARCO Tower 15F
1-8-1, Shimo-Meguro, Meguro-ku,
Tokyo 153-0064
Japan
0120 191014 or +81 3 5437 9125
[email protected]
Asia/Pacific:
Freescale Semiconductor China Ltd.
Exchange Building 23F
No. 118 Jianguo Road
Chaoyang District
Beijing 100022
China
+86 10 5879 8000
[email protected]
For Literature Requests Only:
Freescale Semiconductor Literature Distribution Center
1-800-441-2447 or +1-303-675-2140
Fax: +1-303-675-2150
[email protected]
Information in this document is provided solely to enable system and software
implementers to use Freescale Semiconductor products. There are no express or
implied copyright licenses granted hereunder to design or fabricate any integrated
circuits or integrated circuits based on the information in this document.
Freescale Semiconductor reserves the right to make changes without further notice to
any products herein. Freescale Semiconductor makes no warranty, representation or
guarantee regarding the suitability of its products for any particular purpose, nor does
Freescale Semiconductor assume any liability arising out of the application or use of any
product or circuit, and specifically disclaims any and all liability, including without
limitation consequential or incidental damages. “Typical” parameters that may be
provided in Freescale Semiconductor data sheets and/or specifications can and do vary
in different applications and actual performance may vary over time. All operating
parameters, including “Typicals”, must be validated for each customer application by
customer’s technical experts. Freescale Semiconductor does not convey any license
under its patent rights nor the rights of others. Freescale Semiconductor products are
not designed, intended, or authorized for use as components in systems intended for
surgical implant into the body, or other applications intended to support or sustain life,
or for any other application in which the failure of the Freescale Semiconductor product
could create a situation where personal injury or death may occur. Should Buyer
purchase or use Freescale Semiconductor products for any such unintended or
unauthorized application, Buyer shall indemnify and hold Freescale Semiconductor and
its officers, employees, subsidiaries, affiliates, and distributors harmless against all
claims, costs, damages, and expenses, and reasonable attorney fees arising out of,
directly or indirectly, any claim of personal injury or death associated with such
unintended or unauthorized use, even if such claim alleges that Freescale
Semiconductor was negligent regarding the design or manufacture of the part.
Freescale™ and the Freescale logo are trademarks of Freescale Semiconductor, Inc.
All other product or service names are the property of their respective owners.
© Freescale Semiconductor, Inc. 2009. All rights reserved.
RoHS-compliant and/or Pb-free versions of Freescale products have the functionality and electrical
characteristics of their non-RoHS-compliant and/or non-Pb-free counterparts. For further
information, see http:/www.freescale.com or contact your Freescale sales representative.
For information on Freescale’s Environmental Products program, go to http://www.freescale.com/epp.
MMA1270KEG
Rev. 0
11/2009