12-DigitalAnalog

12-DigitalAnalog - Digital to analog conversion Digital to...

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igital to analog conversion Digital to analog conversion Analog to digital conversion ECE 2534 Packet 12 1
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Why? Need to i nterface with the real (analog) world Sensor ADC μController DAC Actuator ± Transducer ² A device that converts one form of energy to a different form ² E.g., a photodiode produces an electrical current that is a function of the photons striking the device Packet 12 2
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± Example phenomena (and sensors) ² Position (potentiometer, etc.) irection yroscope) ² Direction (gyroscope) ² Temperature (thermistor) ² Force, pressure (strain gauge, etc.) ² Sound (microphone) ² Light intensity (photodiode, camera) adio signal ntenna) ² Radio signal (antenna) ± Example outputs (and actuators) osition orientation otor) ² Position, orientation (motor) ² Sound (acoustic speaker) ² Current, etc. (relay, solenoid, Packet 12 3 SCR, etc.)
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First: the output side Packet 12 4
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Digital-to-Analog Conversion ± Goal ² Convert a digital value to an analog voltage sually an unsigned binary number 8 to 16 bits ² Usually an unsigned binary number, 8 to 16 bits ² Common output range: a few volts, such as 0 to Vcc or –12 V to +12 V ± Normally use a linear mapping ommon concerns ± Common concerns ² Resolution ccuracy Packet 12 5 ² Accuracy ² Conversion speed
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Digital-to-Analog Conversion ypical conversion ± Typical conversion ( ) OUT RefHig hR e fLow RefLow n D VV V V ⎛⎞ =− + ⎜⎟ ² V OUT = analog output voltage 2 ⎝⎠ ² D = binary input value ² n = number of bits pper reference voltage ² V RefHigh = upper reference voltage ² V RefLow = lower reference voltage = “offset” ² V efHigh V efLow is called the “span” Packet 12 6 ( RefHigh RefLow )p ² “Resolution” is ( V RefHigh –V RefLow ) / (2 n )
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Digital-to-Analog Conversion onversion on Spartan board ±
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This note was uploaded on 02/07/2011 for the course ECE 2534 taught by Professor Abbott during the Fall '10 term at Virginia Tech.

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12-DigitalAnalog - Digital to analog conversion Digital to...

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