a
FEATURES
V
OUT
= V
Y
V
Z
V
X
m
Real-Time Analog
Computational Unit (ACU)
AD538
FUNCTIONAL BLOCK DIAGRAM
I
Z 1
V
Z 2
B
3
+10V
4
100
+2V
5
+V
S 6
–V
S 7
V
O 8
I
9
INTERNAL
VOLTAGE
REFERENCE
OUTPUT
25k
ANTILOG
LOG
11
I
Y
18
A
Transfer Function
25k
LOG
RATIO
17
D
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
PRODUCT DESCRIPTION
16
I
X
100
25k
15
V
X
14
SIGNAL
GND
PWR
GND
AD538
13
12
C
25k
10
V
Y
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
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
which may result from its use. No license is granted by implication or
otherwise under any patent or patent rights of Analog Devices.
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 781/329-4700
World Wide Web Site: http://www.analog.com
Fax: 781/326-8703
© Analog Devices, Inc., 1999
AD [ ANALOG DEVICES ]
