TLV277xEP, TLV277xAEP

FAMILY OF 2.7V HIGHSLEW RATE RAILTORAIL OUTPUT

OPERATIONAL AMPLIFIERS WITH SHUTDOWN

SGLS317A − OCTOBER 2005 − REVISED SEPTEMBER 2007

28

POST OFFICE BOX 655303

APPLICATION INFORMATION

using the TLV2772 as an accelerometer interface

The schematic (see Figure 63) 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 k

Ω

C1

0.22

µF

R2

1 M

Ω

R3

10 k

Ω

1.23 V

C2

2.2 nF

R4

100 k

Ω

3 V

R5

1 k

Ω

C3

0.22

µF

1/2

TLV2772

Signal Conditioning

Output to

TLV1544 (ADC)

R6

2.2 k

Ω

1.23 V

3 V

TLV431

C

R

A

4

8

1

2

3

Voltage Reference

Figure 63. 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 63 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-k

Ω 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.