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1 Deptartment of Measurement and Information Systems VIMIA347-Embedded and Ambient Systems Digital to Analog Converters Lecturer: Krébesz, Tamás
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Deptartment of Measurement and Information Systems
VIMIA347-Embedded and Ambient Systems
Digital to Analog Converters
Lecturer: Krébesz, Tamás
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Deptartment of Measurement and Information Systems
VIMIA347-Embedded and Ambient Systems
Digital to analog converter (DAC)
• Idea
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Deptartment of Measurement and Information Systems
VIMIA347-Embedded and Ambient Systems
Kelvin divider (string DAC)
• Simplest voltage output DAC– Number of resistances: 2^N– Number of switches: 2^N– Output impedance is code dependent– Monoton– Small code change transient (glitch)
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Deptartment of Measurement and Information Systems
VIMIA347-Embedded and Ambient Systems
• Block diagram of Kelvin divider
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Deptartment of Measurement and Information Systems
VIMIA347-Embedded and Ambient Systems
• Segmented Kelvin divider
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Deptartment of Measurement and Information Systems
VIMIA347-Embedded and Ambient Systems
• Kelvin divider and R-2R ladder network
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Deptartment of Measurement and Information Systems
VIMIA347-Embedded and Ambient Systems
Current output DAC
• Simplest case:
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Deptartment of Measurement and Information Systems
VIMIA347-Embedded and Ambient Systems
• Current output DAC with current sources
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Deptartment of Measurement and Information Systems
VIMIA347-Embedded and Ambient Systems
• Binary weighted current output DAC
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Deptartment of Measurement and Information Systems
VIMIA347-Embedded and Ambient Systems
• Note: difficult to fabricate on IC due to largeresistors or current ratios for highresolutions
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Deptartment of Measurement and Information Systems
VIMIA347-Embedded and Ambient Systems
• Remember:
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Deptartment of Measurement and Information Systems
VIMIA347-Embedded and Ambient Systems
R-2R ladder network
• One of the most common DAC building-block structure
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Deptartment of Measurement and Information Systems
VIMIA347-Embedded and Ambient Systems
• Current output
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Deptartment of Measurement and Information Systems
VIMIA347-Embedded and Ambient Systems
• Voltage output
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Deptartment of Measurement and Information Systems
VIMIA347-Embedded and Ambient Systems
Double buffering in DAC
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Deptartment of Measurement and Information Systems
VIMIA347-Embedded and Ambient Systems
• Input representation is arbitrary• Input can be asynchronous while output
buffer works at constant frequency
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Deptartment of Measurement and Information Systems
VIMIA347-Embedded and Ambient Systems
DAC dynamic performace
• Settling time
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Deptartment of Measurement and Information Systems
VIMIA347-Embedded and Ambient Systems
• Glitch: code change transient
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Deptartment of Measurement and Information Systems
VIMIA347-Embedded and Ambient Systems
– Cahracterized by Glitch pulse area
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Deptartment of Measurement and Information Systems
VIMIA347-Embedded and Ambient Systems
• Example of measuring dynamic features
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Deptartment of Measurement and Information Systems
VIMIA347-Embedded and Ambient Systems
Sigma-Delta DAC
• Single bit
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Deptartment of Measurement and Information Systems
VIMIA347-Embedded and Ambient Systems
• Multi bit
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