Texas Instruments ADS126 EVM-PDK Series, User Manual, Page: 13 / 38

47pF
C4
47pF
C1
GND
AIN0
AIN1
IN0
IN1
GND
AIN2
AIN3
IN2
IN3
AIN4
AIN5
IN4
IN5
47pF
C26
47pF
C23
AIN6
AIN7
(EXT REF3 P)
(EXT REF3 N)
IN0
IN1
IN2
IN3
IN4
IN5
IN6
IN7
AINCOM
GND
CM f-3dB = 72 MHz
DM f-3dB = 16.9 kHz
INPUT FILTERING
TERMINAL BLOCK
Top Side
IN0
IN1
IN2
IN3
IN4
IN5
IN6
IN7
GND
Bottom Side
GND
IN7
IN6
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
J3
DAUGHTER-ANALOG
REFOUT
(Connects to MMB0)
ED555/2DS
1
2
J4
Thermocouple
Cold Junction = GND
47 R21
GND
X2Y Capacitor
100nF
C18
100nF
C25
ED555/10DS
1
2
3
4
5
6
7
8
9
10
J2
499 R26
GND
AIN8
AIN9
CM f-3dB = 319 kHz
DM f-3dB = 1.59 kHz
FILTERING
1nF
C34
1
2
JP5
Sensor Bias
(Test SIG P)
(Test SIG N)
499 R28
100nF
C36
1nF
C37
(EXT REF2 P)
(EXT REF2 N)
(EXT REF1 N)
(EXT REF1 P)
AVSS Connection
47 R16
47 R18
47pF
C21
47pF
C16
GND
GND GND
X2Y Capacitor
47 R20
47 R12
47 R8
47 R6
47 R1
GND GND
X2Y Capacitor
100nF
C9
47pF
C11
47pF
C7
GND
NI
R24
IN7
NI
R22
IN6
1
2
JP3
AVSS
2.2k @ 25°C
t°
R
T
1
12k
R23
Thermistor (for CJC)
Jumper
NI C2
NI C8
NI C35
100nF
C3
Jumper
AINCOM
NI
R2
NI
R10
3.9k
R17
REFOUT1
IN1
IN2
GND
47pF
C22
AINCOM
AINCOM1
620
R19
R19 increases REF3N voltage to >0.3V when used with
500uA ID AC in single supply and ratiometric configurations
GND GND
NI C17
GND GND
NI C24
X2Y Capacitor
X2Y Capacitor
MMB0 passes signals through to J10
TERMINAL BLOCK
Top Side
1.2k
R25
Input
GND
Configured for 250uA ID AC
1
2
JP1
Ratiometric
Connection
IN4
IN6
Jumper
in single supply configuration
(Install 0-Ohms in R22 & R24)
R17 sets up a 1.95V reference
voltage with 500uA ID AC
NI
R31
GND
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ADS126xEVM Hardware
2.6 Analog Inputs
The ADS126x has a total of 11 analog input pin: AIN0 through AIN9 plus a common reference input,
AINCOM. This design allows the ADS126x to be configured for up to five differential input pairs, ten
single-ended inputs referenced to a common voltage, or a combination of single-ended and differential
inputs. The flexible input multiplexer of the ADS126x allows any two inputs to be selected for either the
positive or negative ADC input.
When measuring single-ended input signals, any input pin may be used as a common voltage reference.
However, AINCOM is specially designated to serve this purpose because it provides a bias voltage (level-
shift function) for floating sensors to meet the common-mode voltage requirements of the ADS126x inputs.
All of the analog inputs to the ADC are pinned out on the ADS126xEVM. The supporting circuitry provides
filtering and ratiometric connections for a variety of sensors. Additionally, a separate terminal block (J4) is
provided for thermocouple inputs.
Figure 10 shows the schematic of the ADS126xEVM analog input
circuitry.
Figure 10. Analog Input Support Circuitry on the ADS126xEVM
13 SBAU206 – April 2015 ADS126xEVM-PDK
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