Analog to Digital Conversion EE3376
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