Datasheet

Evaluation Board User Guide UG-224
Rev. 0 | Page 3 of 20
EVALUATION BOARD HARDWARE
POWER SUPPLIES
There are several power supply options on the AD7194
evaluation board, which include the following:
• The EVAL-AD7194EBZ evaluation board is powered via
the 5 V supply from the USB connector, J51. This 5 V supply
can power the AD7194 directly. Place the J1 link in the
5 V USB position.
• The 5 V supply from the USB connector can be regulated to
3.3 V using the on-board ADP3330ARTZ3.3, a high precision,
low power, 3.3 V output voltage regulator. Therefore, using
the J1 link, the 3.3 V can be used as the power supply to the
AD7194. Place the J1 link in the 3.3 V position.
• An external power supply can be applied via J6. Place the
J1 link in the EXT position.
SOCKETS
There are five sockets relevant to the operation of the AD7194
on this evaluation board. The functions of these sockets are
outlined in Table 1.
NOISE TEST
Header J5 allows the user to perform noise testing of the AD7194.
Use Header J4 to apply the reference to the AD7194. With the
links on both headers, as configured per Figure 2, the analog input
and reference are applied to the AD7194, as shown in Figure 3.
J5 J4
A
V
D
D
A
I
N
7
A
I
N
8
R
E
F
–
R
E
F
+
A
V
D
D
09553-002
Figure 2. Link Positions for Noise Testing
AD7194
AV
DD
A
V
DD
REFIN1(+)
1kΩ
1kΩ
AIN7
AIN8
REFIN1(–)
09553-003
Figure 3. Noise Test Connections
As per Figure 2, inserting the links in Header J5 connects a
resistor network to the AD7194. The reference to the ADC is
provided by AV
DD
. The resistor divider generates a bias voltage
of approximately AV
DD
/2. Channel AIN7 and Channel AIN8 are
connected to this voltage. Conversions 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 EVAL-AD7194EBZ so that the
part can also be evaluated using an absolute reference. The
reference can be connected to the REFIN1(+)/REFIN1(−) pins
of the AD7194 by connecting the links of J4 as shown in Figure 4.
J4
R
E
F
–
R
E
F
+
A
V
D
D
09553-004
Figure 4. Connecting an Absolute Reference to the AD7194
CONNECTING THE AD7194 TO AN EXTERNAL
MICROCONTROLLER
The EVAL-AD7194EBZ can be connected to an external micro-
controller using Header J2. With all links in place, the AD7194
is connected to the on-board microcontroller. However, with these
links removed, the AD7194 is disconnected from the evaluation
board microcontroller. The user can then use Header J2 to
interface the AD7194 to the external microcontroller.
Table 1. Socket Functions
Socket Description
REFIN1(+)
Subminiature BNC (SMB) connector. This socket is used in conjunction with REFIN1(−) to apply an external reference to the
AD7194. The voltage for the REFIN1(+) input of the AD7194 is applied to this socket.
REFIN1(−)
Subminiature BNC (SMB) connector. This socket is used in conjunction with REFIN1(+) to apply an external reference to the
AD7194. The voltage for the REFIN1(−) input of the AD7194 is applied to this socket.
AIN7 Subminiature BNC (SMB) connector. Use this socket to apply an analog input signal to AIN7.
AIN8 Subminiature BNC (SMB) connector. Use this socket to apply an analog input signal to AIN8.
MCLK Subminiature BNC (SMB) connector. Use this socket to apply an external clock source to the AD7194.