Datasheet
SLOS209G − JANUARY 1998 − REVISED FEBRUARY 2004
36
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APPLICATION INFORMATION
using the TLV2772 as an accelerometer interface
The schematic, shown in Figure 62, shows the ACH04-08-05 interfaced to the TLV1544 10-bit analog-to-digital
converter (ADC).
The ACH04-08-05 is a shock sensor designed to convert mechanical acceleration into electrical signals. The
sensor contains three piezoelectric sensing elements oriented to simultaneously measure acceleration in three
orthogonal, linear axes (x, y, z). The operating frequency is 0.5 Hz to 5 kHz. The output is buffered with an
internal JFET and has a typical output voltage of 1.80 mV/g for the x and y axis and 1.35 mV/g for the z axis.
Amplification and frequency shaping of the shock sensor output is done by the TLV2772 rail-to-rail operational
amplifier. The TLV2772 is ideal for this application as it offers high input impedance, good slew rate, and
excellent dc precision. The rail-to-rail output swing and high output drive are perfect for driving the analog input
of the TLV1544 ADC.
_
+
1 Axis ACH04−08−05
Shock Sensor
3 V
1.23 V
R1
100 kΩ
C1
0.22 µF
R2
1 MΩ
R3
10 kΩ
1.23 V
C2
2.2 nF
R4
100 kΩ
3 V
R5
1 kΩ
C3
0.22 µF
1/2
TLV2772
Signal Conditioning
Output to
TLV1544 (ADC)
R6
2.2 kΩ
1.23 V
3 V
TLV431
C
R
A
4
8
1
2
3
Voltage Reference
Figure 62. Accelerometer Interface Schematic
The sensor signal must be amplified and frequency-shaped to provide a signal the ADC can properly convert
into the digital domain. Figure 62 shows the topology used in this application for one axis of the sensor. This
system is powered from a single 3-V supply. Configuring the TLV431 with a 2.2-kΩ resistor produces a reference
voltage of 1.23 V. This voltage is used to bias the operational amplifier and the internal JFETs in the shock
sensor.