AD598JR 查看數據表（PDF） - Analog Devices
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AD598JR Datasheet PDF : 16 Pages
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AD598–Typical Characteristics (at +25؇C and VS = ؎15 V, unless otherwise noted)
40
120
OFFSET PSRR 12–15V
0
80
OFFSET PSRR 15–18V
–40
40
GAIN PSRR 12–15V
–80
20
–120
GAIN PSRR 15–18V
0
–160
–20
–200
–40
–240
–60
–60
–20 0 20
60
100
140
TEMPERATURE – °C
Figure 1. Gain and Offset PSRR vs. Temperature
5
–80
–60
–20 0 20
60
100
140
TEMPERATURE – °C
Figure 2. Typical Gain Drift vs. Temperature
20
0
OFFSET CMRR ± 3V
–5
10
–10
–15
0
–20
GAIN CMRR ± 3V
–25
–10
–30
–35
–60
–20 0 20
60
100
140
TEMPERATURE – °C
Figure 3. Gain and Offset CMRR vs. Temperature
–20
–60
–20 0 20
60
100
140
TEMPERATURE – °C
Figure 4. Typical Offset Drift vs. Temperature
THEORY OF OPERATION
A block diagram of the AD598 along with an LVDT (Linear
Variable Differential Transformer) connected to its input is
shown in Figure 5. The LVDT is an electromechanical trans-
ducer whose input is the mechanical displacement of a core and
whose output is a pair of ac voltages proportional to core posi-
tion. The transducer consists of a primary winding energized by
EXCITATION (CARRIER)
VA
11
32
OSC
AMP
17
AD598
LVDT
10
VB
A–B
A+B
FILTER AMP
16 VOUT
Figure 5. AD598 Functional Block Diagram
an external sine wave reference source, two secondary windings
connected in series, and the moveable core to couple flux be-
tween the primary and secondary windings.
The AD598 energizes the LVDT primary, senses the LVDT
secondary output voltages and produces a dc output voltage
proportional to core position. The AD598 consists of a sine
wave oscillator and power amplifier to drive the primary, a de-
coder which determines the ratio of the difference between the
LVDT secondary voltages divided by their sum, a filter and an
output amplifier.
The oscillator comprises a multivibrator which produces a
triwave output. The triwave drives a sine shaper, which pro-
duces a low distortion sine wave whose frequency is determined
by a single capacitor. Output frequency can range from 20 Hz to
20 kHz and amplitude from 2 V rms to 24 V rms. Total har-
monic distortion is typically –50 dB.
The output from the LVDT secondaries consists of a pair of
sine waves whose amplitude difference, (VA–VB), is proportional
to core position. Previous LVDT conditioners synchronously
detect this amplitude difference and convert its absolute value to
–4–
REV. A
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