ADXL202evaluation board

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6/15/00 4:00PM
a
Dual Axis Accelerometer
Evaluation Board
ADXL202EB
GENERAL DESCRIPTION
The ADXL202EB is a simple evaluation board that allows the
user to quickly evaluate the performance of the ADXL202 dual
axis ± 2
g
accelerometer. Only three additional through-hole
passive components must be added, depending on the bandwidth
required in your application. The ADXL202EB has a 5-pin
0.1-inch spaced header for access to all power and signal lines
that may be attached to a prototyping board (breadboard) or wired
via a standard plug. Two holes are provided for mechanical
attachment of the ADXL202EB to your application.
ADXL202EB
A
V
DD
C5
0.47
F
1
R
SET
ADDED
BY
USER
D
X
OUT
C
Y
OUT
E
COM
ST
B
CIRCUIT DESCRIPTION
The schematic and parts list of the ADXL202EB are shown in
Figure 1 and Table I respectively. The minimal application will
require at least one resistor (R
SET
) added to the board to set the
PWM period (T2). Analog bandwidth may be set by adding
capacitors C2 and C3. Refer to the ADXL202 data sheet for a
complete description of the operation of the accelerometer.
C3
ADDED
BY
USER
C4
2200pF
C1
2200pF
C2
ADDED
BY
USER
Figure 1. ADXL202EB Schematic
The part layout of the ADXL202EB is shown in Figure 2. The
ADXL202EB has two factory- installed 2200 pF capacitors (C1
and C4) at X
FILT
and Y
FILT
to satisfy the minimum filter capacitor
specification of the ADXL202. Your application will likely require
narrower bandwidth (and lower noise), in which case a through-
hole capacitor may be added in parallel in the space provided
at C2 and C3 respectively. When calculating the capacitance
required to achieve the desired analog bandwidth do not forget
to subtract the 2200 pF already on the PCB. The pinout descrip-
tion of the ADXL202EB is shown in Table II.
SETTING THE PERIOD OF THE DUTY CYCLE
MODULATOR
The DCM period is set by R
SET
. Choose a value between 100 k
and 2 M
. See Table III for some typical R
SET
values.
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., 2000
 6/15/00 4:00PM
ADV611/ADV612
Table I. ADXL202EB Parts List
Reference
Value
Function
C1
2200 pF/25V
X
FILT
. Sets X axis analog bandwidth along with C2
C2
Added by User
X
FILT
. Sets X axis analog bandwidth along with C1
C3
Added by User
Y
FILT
. Sets Y axis analog bandwidth along with C4
C4
2200 pF/25V
Y
FILT
. Sets Y axis analog bandwidth along with C3
J1
Connector
All power and signal connection through J1
R1
Added by User
R
SET
. Sets the PWM period (T2)
U1
ADXL202
Dual axis ±2
g
accelerometer
Table II. ADXL202EB Pinout Description
Pin Reference
Pinout
C5
C1
E
GROUND
B
SELF-TEST INPUT
D
X AXIS DUTY CYCLE OUT
C2
C
Y AXIS DUTY CYCLE OUT
A
+V SUPPLY (3 to 5.25 VDC)
R
SET
U1
C4
Table III. DCM Period vs. R
SET
Value
C3
T2 Period
R
SET
J1
1 ms
124 k
EBD
C
A
2 ms
248 k
5 ms
620 k
10 ms
1.24 M
Figure 2. ADXL202EB Part Layout (Top View)
Table IV. Typical X
FILT
and Y
FILT
Values vs. Bandwidth and
Noise Performance
SPECIAL NOTES ON HANDLING
Note that the ADXL202EB is not reverse polarity protected.
Reversing the +V
SUPPLY
and Ground pins will damage the
ADXL202.
X
FILT
, Y
FILT
Bandwidth
RMS Noise
Dropping the ADXL202EB on a hard surface may generate
several thousand
g
of acceleration. Enough to damage the accel-
erometer. Please refer to the ADXL202 data sheet for information
on shock survivability.
0.01
F
500 Hz
12.7 m
g
0.047
F
100 Hz
7 m
g
0.1
F
50 Hz
4.2 m
g
0.47
F
10 Hz
2.3 m
g
SETTING THE ADXL202’S BANDWIDTH
The ADXL202EB is supplied with the minimum specified X
FILT
and Y
FILT
values installed. Your application will likely require a
narrower bandwidth to improve noise performance. See Table
IV for some typical capacitor values.
–2–
REV. 0
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