Texas Instruments ADS7853EVM-PDK, Руководство пользователя, Страница: 7 / 41

AINP
AINN
8200 pF
10
10
+
-
1 k
OPA836
+2.5 V
0.2 V
+4.8 V
1 k
2.5 V
5 V
J1/J2
JP9/JP10 (OPEN)
0.2 V
4.8 V
2.5 V
Unipolar Input Signal
GND or
FSR/2
AINP
AINN
8200 pF
10
10
+
-
1 k
OPA836
+1.25 V
-2.3 V
+2.3 V
1 k
0 V
5 V
J1/J2
JP9/JP10 (CLOSED)
0.2 V
4.8 V
2.5 V
GND or
FSR/2
Bipolar Input Signal
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EVM Analog Interface
Figure 3 shows an example where the ADSxx53EVM is configured to support a bipolar input signal with 2
× V
ref
range at the J1 (JP1.2) and J2 (JP2.2) analog interface connectors.
Figure 3. Bipolar Input Signal Configuration with 2 × V
ref
range
2.4 Unipolar Input-Signal Configuration
When jumpers JP9 and JP10 are open, the inverting amplifier (OPA836) is biased at the appropiate
common-mode voltage level to support unipolar signals on the analog interface connectors. In this
configuration, apply a unipolar input signal with FSR / 2 common-mode voltage.
Figure 4 shows an
example where the ADSxx53EVM is configured to support a unipolar input signal with 2 × V
ref
range at the
J1 (JP1.2) and J2 (JP2.2) analog interface connectors.
Figure 4. Unipolar Input Signal Configuration
2.5 ADSxx53EVM Onboard Reference and ADSxx53 Device Internal Reference
The ADSxx53 dual, simultaneous ADC operates with reference voltages VREF_A and VREF_B present
on pins REFIO_A and REFIO_B, respectively. The ADSxx53 device incorporates two internal individually-
programmable 2.5-V reference sources. Alternatively, the onboard 2.5-V reference, REF5025 (U5), can
also be selected. The reference voltage source is determined by setting bit B6 of the ADC configuration
register. Note that this bit is common to ADC_A and ADC_B. Configure the reference settings on the
ADSxx53EVM-PDK by navigating to the
ADSxx53EVM Settings page on the GUI; see Section 6.3 for
more information. By default, the evaluation module is set up with the onboard external reference source,
with jumpers JP5 and JP6 installed, as shown in
Figure 5 . If the ADSxx53 must be configured with the
internal reference, make sure to remove jumpers JP5 and JP6 before enabling the internal reference.
7 SBAU210A – June 2014 – Revised August 2014 ADS8353EVM-PDK and ADS7853EVM-PDK
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