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Analog to Digital Converters. Arnan Sipitakiat Dept. Computer Engineering, Chiang Mai Univeristy. ADC Methods. Direct conversion (Flash ADC) Successive-Approximation Ramp-compare ADC. Direct Conversion. S/H = sample and hold circuit V in = input voltage V ref = reference voltage.
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Analog to Digital Converters ArnanSipitakiat Dept. Computer Engineering, Chiang Mai Univeristy
ADC Methods • Direct conversion (Flash ADC) • Successive-Approximation • Ramp-compare ADC
S/H = sample and hold circuit Vin = input voltage Vref = reference voltage DAC = Digital-to-Analog converter EOC = end of conversion SAR = successive approximation register Successive-Approximation
Ramp-compare ADC Similar to Successive Approximation, but uses a simple circuit to generate a ramp and measures the time it takes to match the input. The ramp generation circuit is often sensitive to temperature.
Voltage divider: Measuring Resistance R1 = 33K, Vin = 5V ถ้า Rsensor = 66K ค่าที่อ่านจาก GoGo Monitor จะเป็นเท่าใด Vout = Vin x R2 / (R1+R2)
Vo = Vin x R2 / (R1+R2)ADC = 1023 x R2 / (R1+R2) = 1023 x 66 / (33 + 66) = 1023 x 2/3 = 682
Successive-Approximation ADC Voltage Divider
ADC Parameters • Resolution. 8, 10, 12, … bits • Number of analog ports • ADC speed