Datasheet

UG-222 Evaluation Board User Guide
Rev. 0 | Page 4 of 20
NOISE TEST
Header J3 allows the user to perform noise testing of the
AD7190/AD7192. With all links in the vertical position
(see Figure 2), the analog and reference are applied to the
AD7190/AD7192, as shown in Figure 3.
AVDD AIN1 AIN2 AINCOM AGND REF2– REF2+ VREF
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J3
Figure 2. Link Positions for Noise Testing
100Ω
1kΩ
1kΩ
AV
DD
A
V
DD
AD7190/
AD7192
REFIN2(+)
AIN1
AIN2
AINCOM
REFIN2(–)
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Figure 3. Noise Test Connections
As shown in Figure 3, inserting the links in Header J3 connects
a resistor network to the AD7190/AD7192. The reference to
the ADC is provided by AV
DD
. The resistor divider generates
a bias voltage of approximately AV
DD
/2. Channel AIN1 and
Channel AIN2 are connected to this voltage. Therefore, conver-
sions can now be performed using this external short to measure
the rms noise, peak-to-peak noise, and peak-to-peak resolution.
USING AN ABSOLUTE REFERENCE
An ADR421 is included on the AD7190/AD7192 evaluation
board so that the part can also be evaluated using an absolute
reference. The reference can be connected to the REFIN2(+)
and REFIN2(−) pins of the AD7190/AD7192 by connecting the
links of Header J3, as shown in Figure 4.
AVDD AIN1 AIN2 AINCOM AGND REF2– REF2+ VREF
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J3
Figure 4. Connecting an Absolute Reference to the AD7190/AD7192
CONNECTING THE AD7190/AD7192 TO AN
EXTERNAL MICROCONTROLLER
The AD7190/AD7192 evaluation board can be connected to an
external microcontroller using Header J2. With all links in
place, the AD7190/AD7192 are connected to the on-board
microcontroller. However, with these links removed, the
AD7190/AD7192 are disconnected from the evaluation board
microcontroller. The user can then use a header to interface the
AD7190/AD7192 to the external microcontroller.