ADXL150 250 0

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a
50 g, Low Noise, Low Power,
Single/Dual Axis
i
MEM
S
Ò
Accelerometers
ADXL150/ADXL250
6
5 g to
6
FEATURES
Complete Acceleration Measurement System
on a Single Monolithic IC
80 dB Dynamic Range
Pin Programmable
6
50 g or
FUNCTIONAL BLOCK DIAGRAMS
TP
(DO NOT CONNECT)
6
25 g Full Scale
+V
S
ADXL150
GAIN
AMP
+V
S
2
5k
V
Low Noise: 1 mg/
Hz Typical
Low Power: <2 mA per Axis
Supply Voltages as Low as 4 V
2-Pole Filter On-Chip
Ratiometric Operation
Complete Mechanical & Electrical Self-Test
Dual & Single Axis Versions Available
Surface Mount Package
Ö
0.1
m
F
V
OUT
SENSOR
DEMODULATOR
25k
V
BUFFER
AMP
CLOCK
9
SELF-TEST
COM
OFFSET
NULL
TP
(DO NOT CONNECT)
X OFFSET
NULL
ADXL250
25k
V
BUFFER
AMP
+V
S
GAIN
AMP
0.1
m
F
V
OUT
X
DEMODULATOR
SENSOR
GENERAL DESCRIPTION
The ADXL150 and ADXL250 are third generation
5k
V
50
g
sur-
face micromachined accelerometers. These improved replace-
ments for the ADXL50 offer lower noise, wider dynamic range,
reduced power consumption and improved zero
g
bias drift.
The ADXL150 is a single axis product; the ADXL250 is a fully
integrated dual axis accelerometer with signal conditioning on a
single monolithic IC, the first of its kind available on the com-
mercial market. The two sensitive axes of the ADXL250 are
orthogonal (90
±
CLOCK
+V
S
2
5k
V
GAIN
AM
P
V
OUT
Y
SENSOR
DEMODULATOR
25k
V
BUFFER
AMP
SELF-TEST
COM
Y OFFSET
NULL
) to each other. Both devices have their sensitive
axes in the same plane as the silicon chip.
The ADXL150/ADXL250 offer lower noise and improved
signal-to-noise ratio over the ADXL50. Typical S/N is 80 dB,
allowing resolution of signals as low as 10 m
g
, yet still providing
a
°
ratiometric to the power supply, eliminating the need for a volt-
age reference when driving ratiometric A/D converters such as
those found in most microprocessors. A power supply bypass
capacitor is the only external component needed for normal
operation.
The ADXL150/ADXL250 are available in a hermetic 14-lead
surface mount cerpac package specified over the 0°C to +70°C
commercial and –40°C to +85°C industrial temperature ranges.
Contact factory for availability of devices specified over automo-
tive and military temperature ranges.
50
g
full-scale range. Device scale factor can be increased
from 38 mV/
g
to 76 mV/
g
by connecting a jumper between
V
OUT
and the offset null pin. Zero
g
drift has been reduced to
0.4
g
over the industrial temperature range, a 10
improvement
over the ADXL50. Power consumption is a modest 1.8 mA
per axis. The scale factor and zero
g
output level are both
´
i
MEM
S
is a registered trademark of Analog Devices, Inc.
REV. 0
Information furnished by Analog Devices is believed to be accurate and
reliable. However, no responsibility is assumed by Analog Devices for its
use, nor for any infringements of patents or other rights of third parties
which may result from its use. No license is granted by implication or
otherwise under any patent or patent rights of Analog Devices.
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 781/329-4700
World Wide Web Site: http://www.analog.com
Fax: 781/326-8703
© Analog Devices, Inc., 1998
±
ADXL150/ADXL250–SPECIFICATIONS
(T
A
= +25
8
C for J Grade, T
A
= –40
8
C to +85
8
C for A Grade,
V
S
= +5.00 V, Acceleration = Zero g, unless otherwise noted)
ADXL150JQC/AQC
ADXL250JQC/AQC
Parameter
Conditions
Min
Typ Max
Min
Typ Max
Units
SENSOR
Guaranteed Full-Scale Range
±
40
±
50
±
40
±
50
g
Nonlinearity
0.2
0.2
% of FS
Package Alignment Error
1
±
1
±
1
Degrees
Sensor-to-Sensor Alignment Error
±
0.1
Degrees
Transverse Sensitivity
2
±
2
±
2
%
SENSITIVITY
Sensitivity (Ratiometric)
3
Y Channel
33.0
38.0 43.0
mV/
g
X Channel
33.0
38.0 43.0
33.0
38.0 43.0
mV/
g
Sensitivity Drift Due to Temperature Delta from 25
°
C to T
MIN
or T
MAX
±
0.5
±
0.5
%
ZERO
g
BIAS LEVEL
Output Bias Voltage
4
V
S
/2 – 0.35 V
S
/2 V
S
/2 + 0.35 V
S
/2 – 0.35 V
S
/2 V
S
/2 + 0.35 V
Zero
g
Drift Due to Temperature
Delta from 25
°
C to T
MIN
or T
MAX
0.2
0.3
g
ZERO-
g
OFFSET ADJUSTMENT
Voltage Gain
Delta V
OUT
/Delta V
OS PIN
0.45
0.50 0.55
0.45
0.50 0.55
V/V
Input Impedance
20
30
20
30
k
W
NOISE PERFORMANCE
Noise Density
5
1
2.5
1
2.5
m
g
/
Ö
Hz
Clock Noise
5
5
mV p-p
FREQUENCY RESPONSE
–3 dB Bandwidth
900
1000
900
1000
Hz
Bandwidth Temperature Drift
T
MIN
to T
MAX
50
50
Hz
Sensor Resonant Frequency
Q = 5
24
24
kHz
SELF-TEST
Output Change
6
ST Pin from Logic “0” to “1”
0.25
0.40 0.60
0.25
0.40 0.60
V
Logic “1” Voltage
V
S
– 1
V
S
– 1
V
Logic “0” Voltage
1.0
1.0
V
Input Resistance
To Common
30
50
30
50
k
W
OUTPUT AMPLIFIER
Output Voltage Swing
I
OUT
=
±
100
m
A
0.25
V
S
– 0.25 0.25
V
S
– 0.25 V
Capacitive Load Drive
1000
1000
pF
POWER SUPPLY (V
S
)
7
Functional Voltage Range
4.0
6.0
4.0
6.0
V
Quiescent Supply Current
ADXL150
1.8 3.0
mA
ADXL250 (Total 2 Channels)
3.5 5.0
mA
TEMPERATURE RANGE
Operating Range J
0
+70
0
+70
°
C
Specified Performance A
–40
+85
–40
+85
°
C
NOTES
1
Alignment error is specified as the angle between the true axis of sensitivity and the edge of the package.
2
Transverse sensitivity is measured with an applied acceleration that is 90 degrees from the indicated axis of sensitivity.
3
Ratiometric: V
OUT
= V
S
/2 + (Sensitivity
´
V
S
/5 V
´
a) where a = applied acceleration in
g
s, and V
S
= supply voltage. See Figure 21. Output scale factor can be
doubled by connecting V
OUT
to the offset null pin.
4
Ratiometric, proportional to V
S
/2. See Figure 21.
5
See Figure 11 and Device Bandwidth vs. Resolution section.
6
Self-test output varies with supply voltage.
7
When using ADXL250, both Pins 13 and 14 must be connected to the supply for the device to function.
Specifications subject to change without notice.
–2–
REV. 0
ADXL150/ADXL250
ABSOLUTE MAXIMUM RATINGS*
Acceleration (Any Axis, Unpowered for 0.5 ms) . . . . . . 2000
g
Acceleration (Any Axis, Powered for 0.5 ms) . . . . . . . . . 500
g
+V
S
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . –0.3 V to +7.0 V
Output Short Circuit Duration
(V
OUT
, V
REF
Terminals to Common) . . . . . . . . . . . Indefinite
Operating Temperature . . . . . . . . . . . . . . . . . –55
Package Characteristics
Package
u
JA
u
JC
Device Weight
14-Lead Cerpac 110
°
C/W
30
°
C/W
5 Grams
C to +125
°
C
ORDERING GUIDE
C
*
Stresses above those listed under Absolute Maximum Ratings may cause
perma-
nent damage to the device. This is a stress rating only; the functional operation of
the device at these or any other conditions above those indicated in the operational
sections of this specification is not implied. Exposure to absolute maximum rating
conditions for extended periods may affect device reliability.
C to +150
°
Model
Temperature Range
ADXL150JQC
0
°
C to +70
°
C
ADXL150AQC
–40
°
C to +85
°
C
ADXL250JQC
0
°
C to +70
°
C
ADXL250AQC
–40
°
C to +85
°
C
Drops onto hard surfaces can cause shocks of greater than 2000
g
and exceed the absolute maximum rating of the device. Care
should be exercised in handling to avoid damage.
PIN CONNECTIONS
NC
NC
NC
NC
1
14
V
S
NC
ADXL150
NC
NC
V
OUT
SELF-TEST
ZERO g ADJ
TP (DO NOT CONNECT)
TOP VIEW
(Not to Scale)
1
ADXL150
14
ADXL250
14
NC
COMMON
7
8
TOP VIEW
(Not to Scale)
TOP VIEW
(Not to Scale)
A
X
A
X
A
Y
90
8
NC
1
14
V
S
V
S
NC
NC
ZERO g ADJ Y
V
OUT
Y
NC
7
8
7
8
ADXL250
TOP VIEW
(Not to Scale)
POSITIVE A = POSITIVE V
OUT
POSITIVE A = POSITIVE V
OUT
TP (DO NOT CONNECT)
V
OUT
X
Figure 1. ADXL150 and ADXL250 Sensitive Axis
Orientation
NC
COMMON
SELF-TEST
7
8
ZERO g ADJ X
NC = NO CONNECT
NOTE: WHEN USING ADXL250, BOTH PINS 13 AND 14 NEED
TO BE CONNECTED TO SUPPLY FOR DEVICE TO FUNCTION
CAUTION
ESD (electrostatic discharge) sensitive device. Electrostatic charges as high as 4000 V readily
accumulate on the human body and test equipment and can discharge without detection.
Although the ADXL150/ADXL250 feature proprietary ESD protection circuitry, permanent
damage may occur on devices subjected to high energy electrostatic discharges. Therefore, proper
ESD precautions are recommended to avoid performance degradation or loss of functionality.
WARNING!
ESD SENSITIVE DEVICE
REV. 0
–3–
°
Storage Temperature . . . . . . . . . . . . . . . . . . . –65
°
1
ADXL150/ADXL250
GLOSSARY OF TERMS
Acceleration:
Change in velocity per unit time.
Acceleration Vector:
Vector describing the net acceleration
acting upon the ADXL150/ADXL250.
g
:
A unit of acceleration equal to the average force of gravity
occurring at the earth’s surface. A
g
is approximately equal to
32.17 feet/s
2
or 9.807 meters/s
2
.
Nonlinearity:
The maximum deviation of the ADXL150/
ADXL250 output voltage from a best fit straight line fitted to a
plot of acceleration vs. output voltage, calculated as a % of the
full-scale output voltage (at 50
g
).
Resonant Frequency:
The natural frequency of vibration of
the ADXL150/ADXL250 sensor’s central plate (or “beam”). At
its resonant frequency of 24 kHz, the ADXL150/ADXL250’s
moving center plate has a slight peak in its frequency response.
Sensitivity:
The output voltage change per
g
unit of accelera-
tion applied, specified at the V
OUT
pin in mV/
g.
Total Alignment Error:
Net misalignment of the ADXL150/
ADXL250’s on-chip sensor and the measurement axis of the
application. This error includes errors due to sensor die align-
ment to the package, and any misalignment due to installation
of the sensor package in a circuit board or module.
Transverse Acceleration:
Any acceleration applied 90
Zero
g
Bias Level:
The output voltage of the ADXL150/
ADXL250 when there is no acceleration (or gravity) acting
upon the axis of sensitivity. The output offset is the difference
between the actual zero
g
bias level and (V
S
/2).
Polarity of the Acceleration Output
The polarity of the ADXL150/ADXL250 output is shown in
Figure 1. When its sensitive axis is oriented to the earth’s gravity
(and held in place), it will experience an acceleration of +1
g
.
This corresponds to a change of approximately +38 mV at the
output pin. Note that the polarity will be reversed if the package
is rotated 180
clock-
wise (Pin 14 up, Pin 1 down), the ADXL250’s “Y” axis will now
measure +1
g
.
°
8
7
8
A
Y
7
A
X
ADXL150
A
X
14
1
14
ADXL250
1
°
to the
axis of sensitivity.
Transverse Sensitivity Error:
The percent of a transverse
acceleration that appears at V
OUT
.
Transverse Axis:
The axis perpendicular (90
°
) to the axis of
Figure 2. Output Polarity
Acceleration Vectors
The ADXL150/ADXL250 is a sensor designed to measure
accelerations that result from an applied force. It responds to
the component of acceleration on its sensitive X axis (ADXL150)
or on both the “X” and “Y” axis (ADXL250).
sensitivity.
–4–
REV. 0
. The figure shows the ADXL250 oriented so that
its “X” axis measures +1
g
. If the package is rotated 90
°
ADXL150/ADXL250
Typical Characteristics
(@+5 V dc, +25
8
C with a 38 mV/g Scale Factor unless otherwise noted)
5.0
4.0
3.0
2.0
1.0
0
–1.0
–2.0
–3.0
–4.0
–5.0
6
0
–6
–12
–18
PACKAGE
RESONANCE
–24
–30
–36
BEAM
RESONANCE
–42
–48
4.0
4.5
5.0
5.5
6.0
100
1k
10k
POWER SUPPLY VOLTAGE
FREQUENCY – Hz
Figure 3. Typical Sensitivity Error from Ideal Ratiometric
Response for a Number of Units
Figure 6. Typical Output Response vs. Frequency of
ADXL150/ADXL250 on a PC Board that Has Been
Conformally Coated
2.5
30
2.0
20
1.5
1.0
10
0.5
0
0
–0.5
–1.0
–10
–1.5
–2.0
–20
–30
4.0
4.5
5.0
5.5
6.0
–40 –30 –20 –10
0
10 20 30
40
50
60
70
80 90 100
SUPPLY VOLTAGE
TEMPERATURE –
8
C
Figure 4. Offset Error of Zero g Level from Ideal
V
S
/2 Response as a Percent of Full-Scale for a Number
of Units
Figure 7. Typical Zero g Drift for a Number of Units
2.4
2.2
600g
60g
+105
C
500g
50g
2
500g INPUT
+25
C
400g
40g
1.8
300g
30g
–40
8
C
1.6
OUTPUT RESPONSE
200g
20g
1.4
100g
10g
1.2
4
4.5
5
5.5
6
0g
0g
TIME – 0.2ms/Div
SUPPLY VOLTAGE – Volts
Figure 5. Typical Supply Current vs. Supply Voltage
Figure 8. Typical 500 g Step Recovery at the Output
REV. 0
–5–
8
8
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