Digital to Analog Converter / ComparatorD/A •Digital to Analog Converter Performance • 4 bit...
Transcript of Digital to Analog Converter / ComparatorD/A •Digital to Analog Converter Performance • 4 bit...
![Page 1: Digital to Analog Converter / ComparatorD/A •Digital to Analog Converter Performance • 4 bit DAC, 5v range • 5v / 24 →0.3125v/step Code Output 0000 0.0v 0001 0.3125v 0010 0.625v](https://reader033.fdocuments.in/reader033/viewer/2022053122/60aa79f71990f20f03293ade/html5/thumbnails/1.jpg)
Digital to Analog Converter / Comparator
Last updated 5/21/19
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D/A
• Digital to Analog Converter
• Converts a digital word to a fixed analog voltage level
• Many applications• Electronic music
• Audio conversion – cell phones
• Video conversion – digital TV
• Mechanical conversion – valve opening
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D/A
• Digital to Analog Converter
• Converts a digital word to a fixed analog voltage level
• Many types of D/A converters• Resistor DAC
• Current DAC
• Switched Capacitor DAC
• Delta-sigma DAC
• Pulse width modulator
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D/A
• Digital to Analog Converter Performance
• Resolution• n-bit digital word can represent 2n levels
• 8-bit DAC → 256 levels
• Frequency• Outputs are provided at a fixed rate – sampling rate
• Accuracy• Linearity
• Noise
• Many others
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D/A
• Digital to Analog Converter Performance
• 4 bit DAC, 5v range• 5v / 24
→ 0.3125v/step
Code Output
0000 0.0v
0001 0.3125v
0010 0.625v
0011 0.9375v
…
1101 4.0625v
1110 4.375v
1111 4.6875v
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D/A
• Digital to Analog Converter Performance
• 4 bit DAC, 5v range
Code
0010
0011
0100
0011
0111
0101
0011
0110
1001
0000
Tim
e
voltage
time
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D/A
• Digital to Analog Converter Performance
• Typically additional signal conditioning is required to ‘clean up’ the output
voltage
time
voltage
time
filtering
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D/A
• D to A Converter
• Converts a digital word to a fixed voltage level
• example: 4 bit code0000 → Vout = VrefL
1111→ Vout = VrefL+(VrefH-VrefL)(15
16)
b0 contributes 1/16
b1 contributes 1/8
b2 contributes ¼
b3 contributes ½
0110 → Vout = VrefL+(VrefH-VrefL)(1
4+
1
8)
1000 → Vout = VrefL+(VrefH-VrefL)(1
2)
2R
R
R
R
2R
2R
2R
2R
VrefL
“b0”VrefHVrefL
“b1”VrefHVrefL
“b2”VrefHVrefL
“b3”VrefHVrefL
vout
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D/A
• D to A Converter
• Converts a digital word to a fixed voltage level
• example: 4 bit code0000 → Vout = 0
1111→ Vout = VrefH*(15
16)
b0 contributes 1/16
b1 contributes 1/8
b2 contributes ¼
b3 contributes ½
0110 → Vout = VrefH(1
4+
1
8)
1000 → Vout = VrefH(1
2)
2R
R
R
R
2R
2R
2R
2R
Gnd
“b0”VrefHGnd
“b1”VrefHGnd
“b2”VrefHGnd
“b3”VrefHGnd
vout
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D/A
• D to A Converter
• Superposition and Thevenin Equivalents
2R
R
R
R
2R
2R
2R
2R
Gnd
“b0”
“b1”
“b2”
“b3” vout
R
R
R
R
2R
2R
2R
Gnd
“b1”
“b2”
“b3” vout
V+
-
b0 x VrefH2
2R
2R
Gnd
“b0”VrefHGnd
VrefHGnd
VrefHGnd
VrefHGnd
VrefHGnd
VrefHGnd
VrefHGnd
VrefHGnd
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D/A
• D to A Converter
voutvout
R
R
R
2R
2R
Gnd
“b2”VrefHGnd
“b3”VrefHGnd
V+
-
b0 x VrefH4
R
R
R
R
2R
2R
2R
Gnd
“b1”VrefHGnd
“b2”VrefHGnd
“b3”VrefHGnd
V+
-
b0 x VrefH2
R
R
2R
Gnd
V+
-
b0 x VrefH2
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D/A
• D to A Converter
R
R
2R
Gnd
“b3”VrefHGnd
vout
V+
-
b0 x VrefH8
R
R
R
2R
2R
Gnd
“b2”VrefHGnd
“b3”VrefHGnd
vout
V+
-
b0 x VrefH4
R
R
2R
Gnd
V+
-
b0 x VrefH4
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D/A
• D to A Converter
R
Gnd
vout
V+
-
b0 x VrefH16
R
R
2R
Gnd
“b3”VrefHGnd
vout
V+
-
b0 x VrefH8
R
R
2R
Gnd
V+
-
b0 x VrefH8
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D/A
• D to A Converter
• b2 analysis
2R
R
R
R
2R
2R
2R
2R
Gnd
“b0”VrefHGnd
“b1”VrefHGnd
“b2”VrefHGnd
“b3”VrefHGnd
vout
R
R
2R
Gnd
“b3”VrefHGnd
vout
V+
-
b2 x VrefH2
2R
R
R
2R
2R
2R
Gnd
“b2”VrefHGnd
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D/A
• D to A Converter
R
Gnd
vout
V+
-
b2 x VrefH4
R
R
2R
Gnd
“b3”VrefHGnd
vout
V+
-
b2 x VrefH2
R
R
2R
Gnd
V+
-
b2 x VrefH2
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D/A
• D to A Converter
• Vout = ((b0)/16 + (b1)/8 + (b2)/4 + (b3)/2) * VrefH
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D/A
• Example
Code Steps Volts
0000 0000 0 0
0000 0001 1 0.013
0001 0000 16 0.206
0111 1111 127 1.637
1000 0000 128 1.650
1100 0000 192 2.475
1111 1111 255 3.287
3.3V Vref8 bit convertor
3.3v / 28 steps= 12.89mv/step
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Comparator
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Comparator
• Comparator• Compare the voltage of two inputs and generate
‘0’ if minus input > plus input
‘1’ if minus input < plus input
• Open Loop OpAmp
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MSP432P401R
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Comparator
• MSP432 Comparators
• Analog Comparator• 2 blocks
• Input Multiplexing (8)
• Hysteresis Generator
• Programmable RC filter
• Can Generate Interrupt
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Comparator
• Comparator
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Comparator
• ComparatorCOMP_E0->CTL0, …COMP_E1->CTL0, …
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Comparator
• Comparator
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Comparator
• Comparator
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Comparator
• Comparator
τ = R x C8-10 τ recommended for sample time
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Comparator
• Comparator
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Comparator
• Comparator
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Comparator
• Comparator
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Comparator
• Comparator
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Comparator
• Comparator
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Comparator
• Comparator
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Comparator
• Comparator Example
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Comparator
• Comparator Example
/** comparator_example.c** Created on: Jul 27, 2018* Author: johnsontimoj*/
////////////////////////////////////// use port 7.7 as + input (C02)// use port 8.0 as - input (C01)//// use port 7.1 as output//// use a potentiometer to sweep + input// use a fixed divider for – input//// toggle an LED with the output/////////////////////////////////////
// includes#include "msp.h"#include <stdio.h>
// prototypesvoid pin_setup(void);void comp_setup(void);
int main(void){// setup routinespin_setup();comp_setup();
while(1){; // do nothing in the main program
} // end while
return 0;}
void pin_setup(void){// setup pins// Port 8 pins 0 and Port 7 pin 7 "11" select mode// Port 7 pin 1 is output, mode '01'P8->SEL0 |= 0x01; // '11' pin functionalityP8->SEL1 |= 0x01;P7->SEL0 |= 0x80; // '11' pin functionalityP7->SEL1 |= 0x80;
P7->SEL0 |= 0x02; // '01' pin functionalityP7->SEL1 &= ~0x02;P7->DIR |= 0x02;
return;}
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Comparator
• Comparator Example
void comp_setup(void){// setup Comparator E0
// en - in xxx in1 en + in xxx in2// 1 000 0001 1 000 0010COMP_E0->CTL0 = 0x8182;
// xxx x x on normal xx no_ex no_sht no_int no_filt no_inv x// 000 0 0 1 01 00 0 0 0 0 0 0COMP_E0->CTL1 = 0x0500;
// no_ref// 0 00 00000 00 0 0000COMP_E0->CTL2 = 0x0000;
// disable buffer inputs 0 and 2// 0000 0000 0000 0101COMP_E0->CTL3 = 0x0005;
// no interrupts// xxx 0 xx 0 0 xxx x xx x xCOMP_E0->INT = 0x0000;
return;}