Datasheet AD538 (Analog Devices)

Real-Time Analog Computational Unit (ACU) AD538 FEATURES FUNCTIONAL BLOCK DIAGRAM VO = VY(VZ/VX)m transfer function IX D Wide dynamic range (denominator) −1000:1 25kΩ V 100Ω X Simultaneous multiplication and division Resistor-programmable powers and roots LOG B RATIO No external trims required Low input offsets <100 μV 25kΩ VZ A Low error ±0.25% of reading (100:1 range) 100Ω IZ Monolithic construction Real-time analog multiplication, division and +10V INTERNAL VOLTAGE exponentiation +2V REFERENCE V High accuracy analog division with a wide input dynamic range Y 25kΩ I On board +2 V or +10 V scaling reference Y AD538 LOG Voltage and current (summing) input modes Monolithic construction with lower cost and higher C ANTILOG reliability than hybrid and modular circuits I OUTPUT VO
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APPLICATIONS
00 9- 95 00
One- or two-quadrant multiply/divide
Figure 1.
Log ratio computation Squaring/square rooting Trigonometric function approximations Linearization via curve fitting Precision AGC Power functions GENERAL DESCRIPTION
The AD538 is a monolithic real-time computational circuit multiplication and division can be set using the on-chip +2 V or that provides precision analog multiplication, division, and +10 V references, or controlled externally to provide simultaneous exponentiation. The combination of low input and output offset multiplication and division. Exponentiation with an m value voltages and excellent linearity results in accurate computation from 0.2 to 5 can be implemented with the addition of one or over an unusually wide input dynamic range. Laser wafer two external resistors. trimming makes multiplication and division with errors as low Direct log ratio computation is possible by using only the log as 0.25% of reading possible, while typical output offsets of ratio and output sections of the chip. Access to the multiple 100 μV or less add to the overall off-the-shelf performance level. summing junctions adds further to the flexibility of the AD538. Real-time analog signal processing is further enhanced by the Finally, a wide power supply range of ±4.5 V to ±18 V allows 400 kHz bandwidth of the device. operation from standard ±5 V, ±12 V and ±15 V supplies. The overall transfer function of the AD538 is VO = VY(VZ/VX)m. The AD538 is available in two accuracy grades (A and B) over Programming a particular function is via pin strapping. No the industrial (−25°C to +85°C) temperature range and one external components are required for one-quadrant (positive grade (S) over the military (−55°C to +125°C) temperature input) multiplication and division. Two-quadrant (bipolar range. The device is packaged in an 18-lead TO-118 hermetic numerator) division is possible with the use of external level side-brazed ceramic DIP. A-grade chips are also available. shifting and scaling resistors. The desired scale factor for both
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