Datasheet

AD524
Rev. F | Page 21 of 28
WR
CS
+INPUT
G = 10
–INPUT
G = 100
G = 1000
AD7524
OUT2
39kΩ
AD589
MSB
LSB
C1
GND
OUT1
AD524
+V
S
RG
1
RG
2
+
–
–
+
–
+
–V
S
V
REF
+V
S
+V
S
R5
20kΩ
R3
20kΩ
R4
10kΩ
–V
S
R6
5kΩ
1/2
AD712
1/2
AD712
DATA
INPUTS
–V
S
2
8
7
10
6
9
16
13
12
11
3
1
7
6
5
4
1
8
2
3
3
13
12
11
4
15
14
16
1
2
00500-050
AD524C
G = 100
10kΩ
+10V
350Ω350Ω
350Ω350Ω
14-BIT
ADC
0V TO 2V
F.S.
+V
S
–V
S
RG
1
RG
2
+
–
2
8
4
5
10
9
6
7
16
13
12
11
3
1
00500-052
Figure 52. Typical Bridge Application
ERROR BUDGET ANALYSIS
To illustrate how instrumentation amplifier specifications are
applied, review a typical case where an AD524 is required to
amplify the output of an unbalanced transducer. Figure 52
shows a differential transducer, unbalanced by 100 Ω, supplying
a 0 mV to 20 mV signal to an AD524C. The output of the I
A
feeds a 14-bit ADC with a 0 V to 2 V input voltage range. The
operating temperature range is −25°C to +85°C. Therefore, the
largest change in temperature, ∆T, within the operating range is
from ambient to +85°C (85°C − 25°C = 60°C).
Figure 50. Software Controllable Offset
In many applications, complex software algorithms for autozero
applications are not available. For those applications, Figure 51
provides a hardware solution.
AD524
14
15 16
13
GND
CH
1kΩ
ZERO PULSE
AD7510KD
AD711
A1 A2 A3 A4
V
DD
V
SS
200µs
910
1112
–V
S
V
OUT
0.1µF LOW
LEAKAGE
+V
S
RG
1
RG
2
2
8
7
10
6
9
16
13
12
11
3
1
8
1
2
–
+
–
+
00500-051
In many applications, differential linearity and resolution are of
prime importance in cases where the absolute value of a variable is
less important than changes in value. In these applications, only
the irreducible errors (45 ppm = 0.004%) are significant. Further-
more, if a system has an intelligent processor monitoring the
analog-to-digital output, the addition of an autogain/autozero
cycle removes all reducible errors and may eliminate the require-
ment for initial calibration. This also reduces errors to 0.004%.
Figure 51. Autozero Circuit