Texas Instruments ADS127L11EVM, Руководство пользователя, Страница: 7 / 35

2.4 VCOM Buffer
The circuit shown in Figure 2-3 buffers the VCM signal from the ADC and connects this signal to the J8 SMA
connector. This process is useful if the VCOM signal must be connected to an external piece of test equipment
to set the common-mode voltage. A common use case is to connect this signal to the Audio Precision SYS-2722
to set the signal generators common-mode output. This circuit is not required in your end application and is only
used for testing purposes.
1
2
3
4
5
OPA192IDBVR
U7
10µF
C45
37.4
R64
1.00k
R66
10.0k
R65
0.033µF
C47
GND
1µF
16V
C44
1.00k
R63
VCM
VCOM BUFFER
1
2
J9
TSW-102-07-G-S
DNP
1
2 3 4 5
J8
901-144-8RFX
AVSS
AVDD1
AVSS
GND
AVSS
AVSS
100nF
C46
Figure 2-3. VCOM Buffer
2.5 Onboard Voltage Reference
Figure 2-4 shows the REF6225 configuration. This reference includes an integrated wide bandwidth buffer
that makes the REF6225 ideal for driving the switched-capacitor input to the ADS127L11. The EVM provides
a buffer and connections if you choose to use a different voltage reference. This reference is sufficient to
meet the
ADS127L11 24-Bit, Wide-Bandwidth Analog-to-Digital Converter data sheet specifications for dynamic
performance.
AVDD1
VREF_2v5
1µF
16V
C5
25V
22µF
C3
10µF
C2
REFERENCE
0R2
REFP
REFN
Minimum (AVDD1-AVSS) 3V for REF6225
0
R1
0R4
0.047
R5
120k
R6
AVSS
VIN
1
EN
2
SS
3
FILT
4
OUT_S
5
OUT_F
6
GND_F
7
GND_S
8
REF6225IDGKR
U1
TP2
REFN
DNP
TP1
REFP
DNP
TP3
AVSS
DNP
TP4
VrefIN
DNP
0
R89
DNP
0
R90
0
R92
0
R93
DNP
Figure 2-4. Onboard Voltage Reference
www.ti.com EVM Analog Interface
SBAU351 – APRIL 2021
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ADS127L11EVM-PDK Evaluation Module 7
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