Four_quadrant_multiplication_with_the__in_bipolar_operation

Published:2009/7/21 3:09:00 Author:Jessie | From:SeekIC

Four-quadrant multiplication with the AD7520 in bipolar operation. The Intersil AD7520 is an 18-pin multiplying D/A converter. A logic one input at any digital input forces the corresponding ladder switch to steer the bit current to the IOUT1 bus. A logic zero input forces the bit current to the IOUT2 bus. For any code the IOUT1 and IOUT2 bus currents are complements of one another. The current amplifier at IOUT2 changes the polarity of IOUT2 current and the transconductance amplifier at lour output sums the two currents. This configuration doubles the output range but halves the resolution of the D/A convener. For the offset adjustment set VREF to approximately +10 volts and connect all digital inputs to logic one. Adjust the IOUT2 amplifier offset zero pot for 0V ±1 mV at IOUT2 amplifier output. Connect the MSB to logic one and all other bits to logic zero. Adjust IOUT1 offset zero pot for 0V ±mV at VOUT. For the gain adjustment connect all digital inputs, to VDD. Monitor VOUT for a -VREF (1- 2- (n - 1)) volt reading, where n is equal to 10. To increase VOUT connect a series resistor, 0 to 500 ohms, in the lour amplifier feedback loop. To decrease VOUT connect a series resistor, 0 to 500 ohms, between the reference voltage and pin 15 (courtesy Intersil, Inc.).



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