AD538 Datasheet, PDF (1/11 Pages) Analog Devices – Real-Time Analog Computational Unit ACU

a
Real-Time Analog
Computational Unit (ACU)
AD538
FEATURES
V_OUT =
V_Y
 V_Z ^m
 VX 
Transfer Function
Wide Dynamic Range (Denominator) –1000:1
Simultaneous Multiplication and Division
Resistor-Programmable Powers and Roots
No External Trims Required
Low Input Offsets <100 ␮V
Low Error ؎0.25% of Reading (100:1 Range)
+2 V and +10 V On-Chip References
Monolithic Construction
APPLICATIONS
One- or Two-Quadrant Mult/Div
Log Ratio Computation
Squaring/Square Rooting
Trigonometric Function Approximations
Linearization Via Curve Fitting
Precision AGC
Power Functions
FUNCTIONAL BLOCK DIAGRAM
I_Z 1
25k⍀
V_Z 2
LOG
RATIO
18 A
17 D
B3
16 I_X
+10V 4
+2V 5
+V_S 6
100⍀
INTERNAL
VOLTAGE
REFERENCE
100⍀
AD538
25k⍀ ^{15 VX}
SIGNAL
14 _GND
PWR
13 _GND
–V_S 7
V_O 8
OUTPUT
25k⍀
I9
ANTILOG
LOG
12 C
11 I_Y
10 V_Y
25k⍀
PRODUCT DESCRIPTION
The AD538 is a monolithic real-time computational circuit that
provides precision analog multiplication, division and exponen-
tiation. The combination of low input and output offset voltages
and excellent linearity results in accurate computation over an
unusually wide input dynamic range. Laser wafer trimming makes
multiplication and division with errors as low as 0.25% of read-
ing possible, while typical output offsets of 100 µV or less add to
the overall off-the-shelf performance level. Real-time analog
signal processing is further enhanced by the device’s 400 kHz
bandwidth.
The AD538’s overall transfer function is V_O = V_Y (V_Z / V_X)^m.
Programming a particular function is via pin strapping. No
external components are required for one-quadrant (positive
input) multiplication and division. Two-quadrant (bipolar
numerator) division is possible with the use of external level
shifting and scaling resistors. The desired scale factor for both
multiplication and division can be set using the on-chip +2 V or
+10 V references, or controlled externally to provide simulta-
neous multiplication and division. Exponentiation with an m
value from 0.2 to 5 can be implemented with the addition of
one or two external resistors.
Direct log ratio computation is possible by using only the log
ratio and output sections of the chip. Access to the multiple
summing junctions adds further to the AD538’s flexibility.
Finally, a wide power supply range of ± 4.5 V to ± 18 V allows
operation from standard ± 5 V, ± 12 V and ± 15 V supplies.
The AD538 is available in two accuracy grades (A and B) over
the industrial (–25°C to +85°C) temperature range and one
grade (S) over the military (–55°C to +125°C) temperature
range. The device is packaged in an 18-lead TO-118 hermetic
side-brazed ceramic DIP. A-grade chips are also available.
PRODUCT HIGHLIGHTS
1. Real-time analog multiplication, division and exponentiation.
2. High accuracy analog division with a wide input dynamic
range.
3. On-chip +2 V or +10 V scaling reference voltages.
4. Both voltage and current (summing) input modes.
5. Monolithic construction with lower cost and higher reliability
than hybrid and modular circuits.
REV. C
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