Common Mode Amplifier Drive; Voltage Reference; Figure 2-3. Common-Mode Amplifier Drive; Figure 2-4. Voltage Reference - Texas Instruments ADS9218EVM-PDK User Manual

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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.
amplifier and is not populated. When R35 is populated, U8 is unpopulated so that the ADC VCMOUT pin directly
drives the FDA VCM input.

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.
SBAU409 – SEPTEMBER 2022
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Figure 2-3 shows an example of the buffer circuit. R35 bypasses the
C17
5V
GND
10V
0.1µF
4
VCMOUT 3
OPA320AIDBVT
GND

Figure 2-3. Common-Mode Amplifier Drive

U9
5V
2
VIN
1
EN
C30
10V
0.1µF
REF7040QFKHT
GND

Figure 2-4. Voltage Reference

Copyright © 2022 Texas Instruments Incorporated
DNP
VCMOUT
R35
R15
VCM_FDA
1
402
U8
C24
10V
1uF
GND
7
OUTF
6
OUTS
3
GND
4
GND
C31
5
GND
10V
J10
8
GND
10uF
GND GND
Analog Interface
VCM
REFIO
ADS9218EVM-PDK Evaluation Module 7