ADXL210AE-REEL Analog Devices Inc, ADXL210AE-REEL Datasheet - Page 8

• Manufacturer Part Number: ADXL210AE-REEL
• Description: IC ACCELEROMETER LP 8-CLCC
• Manufacturer: Analog Devices Inc

Specifications of ADXL210AE-REEL

• Axis: X, Y
• Acceleration Range: ±10g
• Sensitivity: 100mV/g
• Voltage - Supply: 3 V ~ 5.25 V
• Output Type: Analog
• Bandwidth: 6kHz
• Mounting Type: Surface Mount
• Package / Case: 8-CLCC
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Interface: -

ADXL210E
DEFINITIONS
T1
T2
Duty Cycle Ratio of the “on” time (T1) of the cycle to the total
Pulsewidth
THEORY OF OPERATION
The ADXL210E is a complete, dual-axis acceleration measure-
ment system on a single monolithic IC. It contains a polysilicon
surface-micromachined sensor and signal conditioning circuitry
to implement an open loop acceleration measurement architec-
ture. For each axis, an output circuit converts the analog signal to
a duty cycle modulated (DCM) digital signal that can be decoded
with a counter/timer port on a microprocessor. The ADXL210E
is capable of measuring both positive and negative accelerations
to ± 10 g. The accelerometer can measure static acceleration
forces such as gravity, allowing it to be used as a tilt sensor.
The sensor is a surface micromachined polysilicon structure
built on top of the silicon wafer. Polysilicon springs suspend the
structure over the surface of the wafer and provide a resistance
against acceleration forces. Deflection of the structure is mea-
sured using a differential capacitor that consists of independent
fixed plates and central plates attached to the moving mass. The
fixed plates are driven by 180° out of phase square waves. An
acceleration will deflect the beam and unbalance the differential
capacitor, resulting in an output square wave whose amplitude
is proportional to acceleration. Phase sensitive demodulation
techniques are then used to rectify the signal and determine the
direction of the acceleration.
The output of the demodulator drives a duty cycle modulator
(DCM) stage through a 32 kΩ resistor. At this point a pin is
available on each channel to allow the user to set the signal band-
width of the device by adding a capacitor. This filtering improves
measurement resolution and helps prevent aliasing.
After being low-pass filtered, the analog signal is converted to a
duty cycle modulated signal by the DCM stage. A single resistor
sets the period for a complete cycle (T2), which can be set between
0.5 ms and 10 ms (see TPC 12). A 0 g acceleration produces a
Length of the “on” portion of the cycle.
Length of the total cycle.
Time period of the “on” pulse. Defined as T1 for
cycle (T2). Defined as T1/T2 for the ADXL210E/
ADXL210.
the ADXL210E/ADXL210.
1.06
1.04
1.02
1.00
0.98
0.96
0.94
–45
–30
–15
0
TEMPERATURE – C
15
nominally 50% duty cycle. The acceleration signal can be deter-
mined by measuring the length of the T1 and T2 pulses with
a counter/timer or with a polling loop using a low cost micro-
controller.
An analog output voltage can be obtained either by buffering the
signal from the X
signal through an RC filter to reconstruct the dc value.
The ADXL210E will operate with supply voltages as low as 3.0 V
or as high as 5.25 V.
APPLICATIONS
POWER SUPPLY DECOUPLING
For most applications a single 0.1 µF capacitor, C
adequately decouple the accelerometer from signal and noise
on the power supply. However, in some cases, especially where
digital devices such as microcontrollers share the same power
supply, digital noise on the supply may cause interference on
the ADXL210E output. This may be observed as a slowly
undulating fluctuation of voltage at X
decoupling is needed, a 100 Ω (or smaller) resistor or ferrite
beads, may be inserted in the supply line of the ADXL210E.
30
45
V
DD
60
100
75
FILT
FERRITE BEAD
R
C
SET
DC
and Y
A(g) = (T1/T2 – 0.5)/4%
0g = 50% DUTY CYCLE
T2(s) = R
90
T1
FILT
V
COM
ST
T2
SET
DD
ADXL210E
( )/125M
pin, or by passing the duty cycle
T2
FILT
X
Y
X
Y
OUT
OUT
FILT
FILT
and Y
FILT
Y
FILT
. If additional
DC
X
FILT
, will