Zero Drift, Digitally Programmable
Instrumentation Amplifier Evaluation
Board
AD8231-EVALZ
Rev. 0
Evaluation boards are only intended for device evaluation and not for production purposes.
Evaluation boards are supplied “as is” and without warranties of any kind, express, implied, or
statutory including, but not limited to, any implied warranty of merchantability or fitness for a
particular purpose. No license is granted by implication or otherwise under any patents or other
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Evaluation boards are not authorized to be used in life support devices or systems.
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FEATURES
Two AD8231 circuits
In-amp and op amp
Differential output
Easy to switch jumpers
Decoupled supply lines
GENERAL DESCRIPTION
The AD8231-EVALZ has two AD8231s mounted on it. Z1 is the
AD8231 on the left side of the board. It is configured to allow
access of the in-amp and op amp separately. Z2 is the AD8231
on the right side of the board. It is set up as a differential output
configuration.
Inputs, outputs, references, and the supplies are routed to test
points for easy connectivity.
SDN
,
CS
, and the gain select pins
(A0 to A2) are routed to jumpers. These jumpers control both
AD8231s. When a jumper is in the high position, its corresponding
pin is connected to VS. When the jumper is in the low position,
it is connected to ground.
The PCB has four layers. The top and bottom layers are used for
routing, and the two internal layers are power and ground planes.
EVALUATION BOARD
07016-001
Figure 1.
QUICK START
Set the jumpers as shown in Table 1. These jumper settings ensure
the part is enabled and in a gain of 1.
Table 1. Quick Start Jumper Settings
Function Setting
SDN
High
A2 Low
A1 Low
A0 Low
CS
Low
Connect the ground lead to GND and connect a 5 V supply to
+V
S.
Connect a 1 V source to –INA, and connect a 2 V source to
+INA. 3.5 V should now appear at OUTA.
The output equation for the AD8231 with a gain of 1 is
V
+INA
− V
−INA
+ V
REF
= V
OUT
. As shipped, the evaluation board
has the in-amp reference pin driven to half the supply voltage.
Therefore, the output voltage is 2 V – 1 V + 2.5 V = 3.5 V.
DUAL SUPPLIES
The supplies on the AD8231-EVALZ are labeled VS and GND
because most applications are single supply. However, dual
supplies can also be used with this evaluation board, as long as
the difference between the two supplies is less than 6 V. Simply
connect the negative supply to the GND terminal. For example,
connect +2.5 V to +V
S
and −2.5 V to GND. Any voltage connected
to GND also appears at the GND1, GND2, and GND3 terminals;
therefore, take care when connecting external equipment.
CONFIGURING THE OP AMP
By default, the op amp in Z1 is configured as a unity-gain buffer
driving the in-amp reference pin. A resistor divider at the op amp
input sets the voltage at midsupply. When using this op amp for
other applications, remove R8 and drive the in-amp REF pin
with a different source.
R12
0Ω
RC11
10kΩ
R7
10kΩ
R10
0Ω
R13
0Ω
R8
0Ω
REF
OP_OUT
OP_IN
S
07016-002
Figure 2. Default Op Amp Configuration
