Datasheet

+
-
+
-
ADC141S626
REF
DAC081S101
Micro-
Controller
LMP7702
100 k:
Bridge
Sensor
A
V
= 100 V/V
CSB
SCLK
DOUT
SYNCB
SCLK
DIN
100 k:
2 k:
180:
180:
V
A
V
IO
470 pF
+5V +5V
+5V
+5V
LM4132-4.1
4.7 PF
+
+
4.7 PF
0.1 PF
100:
+
ADC141S626
V
REF
+IN
- IN
GND
V
A
SCLK
D
OUT
CSB
0.1 PF
10 PF
0.1 PF
+
10 PF
+5V
Controller
LM4040-4.1
V
IO
ADC141S626
www.ti.com
SNAS434B NOVEMBER 2007REVISED MARCH 2013
APPLICATION CIRCUITS
The following figures are examples of the ADC141S626 in typical application circuits. These circuits are basic
and will generally require modification for specific circumstances.
Data Acquisition
Figure 44 shows a typical connection diagram for the ADC141S626 operating at V
A
of +5V. V
REF
is connected to
a 4.1V shunt reference, the LM4040-4.1, to define the analog input range of the ADC141S626 independent of
supply variation on the +5V supply line. The V
REF
pin should be de-coupled to the ground plane by a 0.1 µF
ceramic capacitor and a tantalum capacitor of 10 µF. It is important that the 0.1 µF capacitor be placed as close
as possible to the V
REF
pin while the placement of the tantalum capacitor is less critical. It is also recommended
that the V
A
and V
IO
pins of the ADC141S626 be de-coupled to ground by a 0.1 µF ceramic capacitor in parallel
with a 10 µF tantalum capacitor.
Figure 44. Low cost, low power Data Acquisition System
Bridge Sensor Application
Figure 45 shows an example of interfacing a bridge sensor to the ADC141S626. The application assumes that
the bridge sensor requires buffering and amplification to fully utilize the dynamic range of the ADC and thus
optimize the performance of the entire signal path. The amplification stage consists of the LMP7702, a dual
precision amplifier, and some gain setting passive components. The amplification stage offers the benefit of high
input impedance and high amplification capability. On the other hand, it offers no common-mode rejection of
common-mode noise or DC-voltage coming from the bridge sensor.
The DAC081S101, a digital-to-analog converter (DAC), is used to bias the bridge sensor. The DAC provides a
mean for dynamically adjusting the gain of the bridge sensor relative to actual maximum and minimum output
conditions. Another option for biasing the bridge sensor would be powering it from the same +5V power supply
voltage as the V
A
pin on the ADC141S626. This option has the benefit of providing the ideal common-mode input
voltage for the ADC141S626 while keeping design complexity and cost to a minimum. However, any fluctuation
in the +5V supply will still be visible in the converted result. The LM4132-4.1, a 4.1V series reference, is used as
the reference voltage in the application. The ADC141S626, DAC081S101, and the LM4132-4.1 are all powered
from the same +5V voltage source.
Figure 45. Interfacing the ADC141S626 to a Bridge Sensor
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