+

-

+

-

ADC121S705

REF

DAC081S101

Micro-

Controller

LMP7701

LMP7701

200 k:

Pressure

Sensor

0.2 mV/PSI

VA

VA

AV = 100 V/V

CSB

SCLK

DOUT

SYNCB

SCLK

DIN

200 k:

2 k:

180 :

180 :

470 pF

470 pF

2 k:

VA

LM4040-2.5

1 uF

2 k:

+

ADC121S705

VREF

+IN

-IN

GND

VA

SCLK

DOUT

CSB

0.1 PF

4.7 PF

+ 1.0 PF to

4.7 PF

+

10 PF

+5V

Microcontroller

LM4040-2.5

5: to 10:

ADC121S705

www.ti.com

SNAS355B – DECEMBER 2006 – REVISED MARCH 2013

APPLICATION CIRCUITS

The following figures are examples of the ADC121S705 in typical application circuits. These circuits are basic

and will generally require modification for specific circumstances.

Data Acquisition

Figure 61 shows a basic low cost, low power data acquisition circuit. Maximum clock rate with a minimum

sample rate can reduce the power consumption further.

Figure 61. Low cost, low power Data Acquisition System

Pressure Sensor

Figure 62 shows an example of interfacing a pressure sensor to the ADC121S705. A digital-to-analog converter

(DAC) is used to bias the pressure sensor. The DAC081S101 provides a means for dynamically adjusting the

sensitivity of the sensor. A shunt reference voltage of 2.5V is used as the reference for the ADC121S705. The

ADC121S705, DAC081S101, and the LM4040 are all powered from the same voltage source.

Figure 62. Interfacing the ADC121S705 for a Pressure Sensor

Copyright © 2006–2013, Texas Instruments Incorporated

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