Datasheet
+
ADC161S626
V
REF
+IN
-IN
GND
V
A
SCLK
D
OUT
0.1 PF
10 PF
0.1 PF
+
10 PF
+5V
V
IO
CSB
V
CM
OUT
+5V
GND
I
IN
I
OUT
2.5V
2.5V + 2.5V
I
IN
I
OUT
LTSR-1513¶V
LM4120-2.5
ADC
Serial
Interface
ADC161S626
V
REF
Micro-
Controller
A
V
= 2 V/V
CSB
SCLK
DOUT
180:
V
A
V
IO
470 pF
+5V +3.3V
+3.3V
+5V
LM4120-2.5
4.7 PF
+
0.1 PF4.7 PF
+
+
-
+
-
LMP7732
20 k:
100mV Full
Scale
20 k:
2 k:
+
-
2 k:
LMP7731
2 k:
1 k:
1 k:
V
A
Bridge
Sensor
V
BR
A
V
= 20 V/V
V
CM
+
-
ADC161S626
V
REF
Micro-
Controller
CSB
SCLK
DOUT
V
A
V
IO
470 pF
+5V +3.3V
+3.3V
+5V
LM4120-4.1
4.7 PF
+
0.1 PF4.7 PF
+
+
-
+
-
+
-
LMP7732
20 k:
100mV Full
Scale
20 k:
2 k:
180:
180:
Bridge
Sensor
V
BR
A
V
= 40 V/V
ADC161S626
SNAS468C –SEPTEMBER 2008–REVISED MARCH 2013
www.ti.com
A separate power supply (V
BR
) is assumed to be biasing the bridge sensor but another option for biasing the
bridge sensor would be powering it from the +5V power supply. This option has the benefit of providing the ideal
common-mode input voltage for the ADC161S626, while keeping design complexity and cost to a minimum.
However, any fluctuation in the +5V supply will still be visible on the differential input to the amplification stage.
The LM4120-4.1, a 4.1V series reference, and the LM4120-2.5, a 2.5V series reference, are used as the
reference voltages in the respective application drawings. The application in Figure 49 is limited to a V
REF
of 2.5V
or less because of the single-ended configuration of the differential ADC161S626, as discussed in Single-Ended
Input Operation. The ADC161S626 and the LM4120's are all powered from the same +5V voltage source.
Figure 48. Differential Application for a Bridge Sensor
Figure 49. Single-Ended Application for a Bridge Sensor
Current Sensing Application
Figure 50 shows an example of interfacing a current transducer to the ADC161S626. The current transducer
converts an input current into a voltage that is converted by the ADC. Since the output voltage of the current
transducer is single-ended and centered around a common-mode voltage (V
CM
) of 2.5V, the ADC161S626 is
configured with the output of the transducer driving the non-inverting input and V
CM
of the transducer driving the
inverting input. The output of the transducer has an output range of ±2.5V around V
CM
of 2.5V. As a result, a
series reference voltage of 2.5V is connected to the ADC161S626. This will allow all of the codes of the
ADC161S626 to be available for the application. This configuration of the ADC161S626 is referred to as a single-
ended application of a differential ADC. All of the elements in the application are conveniently powered by the
same +5V power supply, keeping circuit complexity and cost to a minimum.
Figure 50. Interfacing the ADC161S626 to a Current Transducer
24 Submit Documentation Feedback Copyright © 2008–2013, Texas Instruments Incorporated
Product Folder Links: ADC161S626