1. Arnan Sipitakiat Dept. Computer Engineering, Chiang Mai Univeristy

2. ADC Methods Direct conversion (Flash ADC) Successive-Approximation Ramp-compare ADC

3. Direct Conversion

4. Successive-Approximation DAC = Digital-to-Analog converter EOC = end of conversion SAR = successive approximation register S/H = sample and hold circuit V in = input voltage V ref = reference voltage

5. 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.

6. R1 = 33K, Vin = 5V ถ้า Rsensor = 66K ค่าที่อ่านจาก GoGo Monitor จะเป็นเท่าใด Vout = Vin x R2 / (R1+R2) Voltage divider: Measuring Resistance

7. Vo = Vin x R2 / (R1+R2) ADC = 1023 x R2 / (R1+R2) = 1023 x 66 / (33 + 66) = 1023 x 2/3 = 682

8. Successive-Approximation ADC Voltage Divider

9. ADC Parameters Resolution. 8, 10, 12, … bits Number of analog ports ADC speed