AD623-EVAL [ADI]
Evaluation Board for the AD623;
| 型号： | AD623-EVAL |
| 厂家： | 
ADI |
| 描述： | Evaluation Board for the AD623 |
| 文件： | 总4页 (文件大小：287K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
Evaluation Board for the AD623
AD623-EVALZ
offset voltage, apply an output reference, or provide shield
drivers with user-supplied components. The board is shipped
with a surface-mount package installed, and it has an alternative
footprint for a through-hole, 8-lead PDIP.
FEATURES
Accepts SOIC or PDIP packages
Configurable for dual or single supplies
Provision for optional circuitry
Shield driver
BASIC OPERATION
Adjustable offset/reference
The AD623 converts a differential signal to a single-ended signal
with respect to a reference. User-supplied power supplies
connect +VS, –VS, and ground to pins of the AD623 on the
evaluation board. The differential signal is applied to the +IN
and –IN pins of the AD623, and the output is monitored at the
in-amp’s OUTPUT pin. Figure 2 shows the component layout
and location of connections.
GENERAL DESCRIPTION
The AD623-EVALZ is an easy-to-use accessory for evaluating
the AD623 instrumentation amplifier. In addition to the basic
in-amp connection, circuit options enable the user to adjust the
FUNCTIONAL BLOCK DIAGRAM
GND2
+IN
REMOVE W3 AND W4 FOR AC COUPLING.
R2
W3
100Ω
+V
S
C1, 0.1µF
+V
AUX
R3
1
COMPONENTS IN SHADED AREAS
ARE USER SUPPLIED.
C6
0.1µF
100kΩ
C4
0.1µF
W9
A3
+
8
3
2
3
8
1
W1
7
A2
W8
+GUARD
–GUARD
+R
G
2
2
6
R5
R6
W10
R
OUTPUT
OUTPUT
G
1
2
REF
W5
R8
–R
W12
G
5
6
5
4
7
–
W2
A2
EXT_REF
+V
W15
W13
W11
4
AUX
C2
0.1µF
R5
1
C5
0.1µF
100kΩ
OP177
CS2
J500
C10
0.1µF
–V
AUX
C3, 0.1µF
W4
–V
S
W14
240µA
–IN
OFFSET ADJ.
C7
0.1µF
R9
R4
100Ω
R1
100k
5.9k
Ω, 1
7
3
%
NOTES
GND1
Ω
6
1
2
2
INSTALL FOR AC COUPLING ONLY.
TO USE GUARD DRIVER, INSTALL R5 AND R6
INSTEAD OF R . R5 AND R6 = 0.5R
A1
2
4
R10
5.9kΩ
.
G
G
C9
0.1µF
, 1%
W7
W6
+V
+V
C8
0.1µF
S
AUX
–V
AUX
CS2
J500
+
C12
10µF
25V
OP177
240µA
GND
–V
AUX
–V
–V
S
AUX
C11
10µF
25V
+
Figure 1.
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
intellectual property by application or use of evaluation boards. Information furnished by Analog
Devices is believed to be accurate and reliable. However, no responsibility is assumed by Analog
Devices for its use, nor for any infringements of patents or other rights of third parties that may result
from its use. Analog Devices reserves the right to change devices or specifications at any time
without notice. Trademarks and registered trademarks are the property of their respective owners.
Evaluation boards are not authorized to be used in life support devices or systems.
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 781.329.4700
Fax: 781.461.3113
www.analog.com
©2007 Analog Devices, Inc. All rights reserved.
AD623-EVALZ
CIRCUIT OPTIONS
GUARD DRIVERS
Single-Supply Operation
When interference from sources such as power lines must be
reduced to levels below those provided by standard shielded
cable, guard drivers may be effective. A guard equalizes the ac
potential between the in-amp input and the cable shield of the
line, effectively reducing the low frequency interference voltage.
A jumper is provided to select between single or dual power
supplies. The board is shipped with W14 in the dual-supply
position. To convert to single supply, place W14 in the position
marked with a ground symbol.
A1 in Figure 2 is a dual op amp AD708 driving the shield(s) of
the input cable(s) from the AD623’s gain resistor pins. The
voltages at these pins are equal to the input voltages plus 0.6 V
(refer to the AD623 data sheet.)
Gain Adjustment
The default gain of the AD623 is unity; installing a resistor at RG
enables the adjustment of gain. RG can be calculated according
to the following equation, or selected from Table 1:
The AD623-EVALZ provides single and differential guards.
Differential guards drive the shields with essentially the same
signals as the inputs, whereas the single guard can be used for
dual conductor cables. In this mode, the +GUARD drives the
shield at ½(VIN DIFF) + 0.6 V.
RG = 100 kΩ/(G − 1)
Table 1. AD623 Standard Value Gain Resistors
Desired
Gain
1% Standard
Value of RG (Ω) Standard 1% Resistors
Calculated Gain Using
2
5
10
20
33
40
50
65
100
200
500
1000
100 k
24.9 k
11 k
5.23 k
3.09 k
2.55 k
2.05 k
1.58 k
1.02 k
499
2
5.02
To activate the guard drivers, +VAUX and –VAUX must be connected.
For shielded cables at both inputs, install the W1, W2, W8,
and W5 jumpers.
10.09
20.12
33.36
40.21
49.78
64.29
99.04
201.4
501
Using a Single Guard
For gains greater than 1, Resistors R6 and R11 (which are each
half the calculated resistance of RG), and the W1, W2, and W10
jumpers are installed. For a gain of 1, either Position R6 or
Position R11 can be shorted to enable the guard driver input.
Connect the shield to +GUARD. On the header pins that do not
bear the ground symbol, insert a shunt across Position W1.
200
100
1001
The guard drivers can be assembled using the components
listed in Table 4.
External Reference or Offset Adjustment
When shipped, the reference of the AD623-EVALZ is
connected to ground. Certain single-supply applications (for
example, an analog-to-digital converter (ADC) connected to
the AD623’s output) require a symmetrical output voltage
centered on a nonzero value. The reference can be equal to half
the supply, or an application-specific voltage can be provided by
an ADC. The user can install a jumper at W13 and connect an
external reference to the EXT_REF pin. To maintain proper
operation of the in-amp, the reference should be provided by a
voltage source.
POWER
OUTPUT
INPUT
Similarly, a provision is made for an offset adjustment of 1.12
V by installing the parts listed in Table 4. Although the A2 and
A3 ICs can be used with a single or dual power supply
connection, A1 requires a dual supply. To enable the offset
feature, install a shunt in Position W11. To adjust the offset of
the AD623, ground both inputs and measure the output voltage.
Adjust Potentiometer R1 for 0 V.
Figure 2. Component Location of In-Amp Evaluation Board
LOAD RESISTOR
Although a load resistor is not required for normal operation,
one can be inserted at Position R8.
Rev. 0 | Page 2 of 4
AD623-EVALZ
APPENDIX
Table 2. Jumpers
Jumper Function
Description
Status
W1
+GUARD select
Allows the shield of the positive input cable to be connected to the guard driver or ground
Not installed
W2
W3
W4
W5
W6
W7
W8
W9
W10
W11
W12
W13
W14
W15
–GUARD select
+Input coupling
–Input coupling
Guard driver –IN
–VS to – VAUX
Allows the shield of the negative input cable to be connected to the guard driver or ground Not installed
Installed; the positive input is dc-coupled
Installed
Installed; the negative input is dc-coupled
Installed
Connects the negative shield guard driver to Pin 1 of the in-amp
Connects the negative supply voltage to the negative auxiliary voltage if of the same value
Connects the positive supply voltage to the positive auxiliary voltage if of the same value
Connects the positive shield guard driver to Pin 8 of the in-amp
Connects the positive shield guard driver to ground
Selects the single-shield guard driver
Connects the reference of the in-amp to the offset-adjustable voltage reference
Connects the reference of the in-amp to ground
Not installed
Not installed
Not installed
Not installed
Not installed
Not installed
Not installed
Installed
+VS to + VAUX
Guard driver +IN
Guard driver +IN
Guard driver +IN
Reference input
Reference input
Reference input
Connects the reference of the in-amp to an external reference supply
Not installed
Connected to –VS
Not installed
In-amp –VS source Connects the in-amp’s –VS pin to GND or to –VS of the evaluation board
Guard driver –IN
Connects the negative shield guard driver to ground
Table 3. Input/Output
I/O
Function
+VS/–VS
GND
+IN/–IN
+GUARD/–GUARD
EXT_REF
Positive and negative rails of the in-amp.
Ground for the board. GND1, GND2, GND3, and GND4 designate pins.
Positive and negative input of the in-amp.
Positive and negative terminals for use with a shielded cable.
External reference input for the in-amp.
OUTPUT
Output of the in-amp.
+VAUX/–VAUX
Auxiliary power rails for guard drivers and offset reference circuitry.
Table 4. User-Supplied Parts for Guard and Offset Circuits
Reference Designation
Guard Drivers
C5, C6
Part
0.1 μF, 25 V ceramic capacitor
A2
AD708JN dual precision op amp
Offset Regulators
C7 to C10
A1
0.1 μF, 25 V ceramic capacitor
OP177 precision op amp
CS1, CS2
R9, R10
J500 240 μA current source
5.9 kΩ, 1% metal film resistor
Rev. 0 | Page 3 of 4
AD623-EVALZ
ORDERING GUIDE
ESD CAUTION
Model
Description
AD623-EVAL
AD623-EVALZ1
Evaluation Board
Evaluation Board
1 Z = RoHS Compliant Part.
©2007 Analog Devices, Inc. All rights reserved. Trademarks and
registered trademarks are the property of their respective owners.
EB07175-0-12/07(0)
Rev. 0 | Page 4 of 4
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