Texas Instruments ADS9218EVM-PDK, User Manual, Page: 7 / 29

2.3 Common Mode Amplifier Drive
The ADS9218 has a common-mode output pin (VCMOUT). The common-mode signal must be buffered to drive
the THS4552 common-mode input pin.
Figure 2-3 shows an example of the buffer circuit. R35 bypasses the
amplifier and is not populated. When R35 is populated, U8 is unpopulated so that the ADC VCMOUT pin directly
drives the FDA VCM input.
10V
0.1µF
C17
GND
5V
GND
VCMOUT
GND
10V
1uF
C24
VCM_FDA
1
2
3
4
5
OPA320AIDBVT
U8
402
R15
VCM
R35
VCMOUT
DNP
Figure 2-3. Common-Mode Amplifier Drive
2.4 Voltage Reference
As shown in Figure 2-4 , the REF7040 is a very low-drift, low-noise, highly stable 4.096-V reference. This
reference can externally drive the REFIO pin of the ADS9218 by installing jumper J10. Alternatively, J10 can be
removed and the ADS9218 can use the internal voltage reference.
VIN
2
EN
1
OUTF
7
OUTS
6
GND
3
GND
4
GND
5
GND
8
REF7040QFKHT
U9
10V
0.1µF
C30
GND
5V
GND
10V
10uF
C31
GND
1 2
J10
REFIO
Figure 2-4. Voltage Reference
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SBAU409 – SEPTEMBER 2022
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ADS9218EVM-PDK Evaluation Module 7
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