analog to digital conversion - utepanalog to digital conversion sampling period analog input digital...

Analog to Digital Conversion

EE3376

Analog to Digital Conversion

Analog to Digital Conversion sampling period

Analog Input

Digital version

56 -40 -65 -41 60 55 -45 -62 -22 50

This is the essence of how CDs or MP3s store music. Stream of digital values represents an audio (analog) waveform. Nyquist Frequency = twice the frequency of the data and is required for sampling to correctly represent an analog signal. MP3s typically sampled at 128ksps (period of ~ 8 microseconds)

5V = 65

-5V = -65

Sampling Theory – Nyquist Freq

Quantization Noise

First – Digital to Analog Converter

DACs are a little less complicated and often used in ADCs. The simplest DAC is a PWM with a low pass filter. Here is an R-2R DAC – fast but high power

A/D circuit – simplified flash a/d

Vref - +

- +

- +

- +

- +

- +

- +

- + R

R

R

R

R

R

R

R

analog Input

8 to 3 E n c o d e r

3

thermometer code

0

0

0

1

1

1

1

1

%100 = 4 digital output Index of highest true input is the output

7/8 Vref

6/8 Vref

5/8 Vref

4/8 Vref

3/8 Vref

2/8 Vref

1/8 Vref

11/16 Vref

Ramp ADC

Successive Approximation ADC

Number of bits = ~number of cycles for conversion

ADC10 ADC Overview

ADC10 Overview

ADC10 Sample Timing

Max sample period = 13 ADC10CLK + Tsample + Tsync

ADC10 Control Register 0

ADC10 Control Register 0 (cont)

ADC10 Control Register 1

ADC10 Control Register 1 (cont)

ADC Lab

X_AXIS = 0, Y_AXIS = 1, Z_AXIS = 2

msp430x22x4_adc10_01

msp430x22x4_adc10_01

msp430x22x4_adc10_01

msp430x22x4_adc10_10

msp430x22x4_adc10_10

msp430x22x4_adc10_10

msp430x22x4_adc10_03

msp430x22x4_adc10_03

msp430x22x4_adc10_13

msp430x22x4_adc10_13

msp430x22x4_adc10_13

msp430x22x4_adc10_14

msp430x22x4_adc10_14

msp430x22x4_adc10_14