Digital to Analog Converter DAC

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Digital to Analog Converter DAC

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1. Digital to Analog Converter (DAC) Trayvon Leslie Orlando Carreon Zack Sosebee

2. Outline Overview Choosing a DAC Specifications Resolution Speed Linearity Settling Time Reference Voltages Errors Errors Types of DAC Binary Weighted Resistor R-2R Ladder Multiplier DAC Non-Multiplier DAC Applications References

3. Overview Digital to Analog Converter (DAC) A digital to analog converter (DAC) is a device that converts digital numbers (binary) into an analog voltage, current, or electric charge output.

4. Overview Typically generates a piecewise continuous function Step Functions The function is continuous between each of the open intervalsTypically generates a piecewise continuous function Step Functions The function is continuous between each of the open intervals

5. Overview Normally a linear function Normally a linear function

6. Overview

7. Overview AD 7224 8-Bit Voltage Output R-2R Output AmplifierAD 7224 8-Bit Voltage Output R-2R Output Amplifier

8. Overview 8 input pins Reference Voltage Variable Resistors Helps to meet the output signal requirements Helps to adjust input signal Offset: Decreasing the offset Decreases the Output Voltage Gain:8 input pins Reference Voltage Variable Resistors Helps to meet the output signal requirements Helps to adjust input signal Offset: Decreasing the offset Decreases the Output Voltage Gain:

9. Choosing a DAC When it comes to your project… There are 6 main specification for choosing your DACWhen it comes to your project… There are 6 main specification for choosing your DAC

10. Specifications The out of the DAC is largely determined by the reference voltage Usually changes with the types of DAC Multiplier: (Internal Reference) Fixed Reference Voltage Less Error Non-Multiplier: (External Reference) Multiplies binary functions Scales ContinuousThe out of the DAC is largely determined by the reference voltage Usually changes with the types of DAC Multiplier: (Internal Reference) Fixed Reference Voltage Less Error Non-Multiplier: (External Reference) Multiplies binary functions Scales Continuous

11. Specifications Similar to the ADC Will be shown from the linear specifications Function of the Reference Voltage and the Number of Bits Increasing the bits decreases the resolution (finer) Number of bits representing an analog signal -- generally ranging from 6 to 24. The higher the number of bits, the higher the resolution of the converter. Generally more accurate too.Similar to the ADC Will be shown from the linear specifications Function of the Reference Voltage and the Number of Bits Increasing the bits decreases the resolution (finer) Number of bits representing an analog signal -- generally ranging from 6 to 24. The higher the number of bits, the higher the resolution of the converter. Generally more accurate too.

12. Specifications Depending on the binary number that How well the device's actual performance across a specified operating range approximates a straight line. Maximum deviation of actual performance relative to a straight line, located such that it minimizes the maximum deviation Depending on the binary number that How well the device's actual performance across a specified operating range approximates a straight line. Maximum deviation of actual performance relative to a straight line, located such that it minimizes the maximum deviation

13. Specifications The rate at which the input digital or binary number are cycled through the DAC The number of conversions per second the DAC is producing. Clock speed: the speed at which the CPU operates.The rate at which the input digital or binary number are cycled through the DAC The number of conversions per second the DAC is producing. Clock speed: the speed at which the CPU operates.

14. Specifications Ideally Usually updated at uniform sampling intervals Each number latched in sequence The time required for the output to reach and remain within a specified error band about its final value, measured from the start of the output transition.Ideally Usually updated at uniform sampling intervals Each number latched in sequence The time required for the output to reach and remain within a specified error band about its final value, measured from the start of the output transition.

15. Specifications

16. Errors Gain Error Deviation in the slope of the ideal curve and with respect to the actual DAC output

17. Errors Offset Error Occurs when there is an offset in the output voltage in reference to the ideal output.

18. Errors Full Scale Error

19. Errors Non-Linearity Differential Non-Linearity: Voltage step size differences vary as digital input increases. Ideally each step should be equivalent.

20. Errors Non-Linearity Integral Non-Linearity: Occurs when the output voltage is non linear. Basically an inability to adhere to the ideal slope.

21. Errors Non-Monotonic Output Error Occurs when the an increase in digital input results in a lower output voltage.

22. Errors Settling Time and Overshoot

23. Errors Settling Time and Overshoot

24. Errors Resolution Inherent errors associated with the resolution More Bits = Less Error and Greater Resolution Less Bits = More Error and Less Resolution

25. Errors Resolution Poor Resolution (1 Bit)

26. Errors Resolution Better Resolution (3 Bit)

27. Types of DAC

28. Types of DAC

29. Types of DAC

30. Types of DAC

31. Types of DAC

32. Types of DAC

33. Types of DAC

34. Types of DAC

35. Types of DAC

37. Types of DAC

38. Types of DAC

39. Types of DAC

40. Applications

41. Applications

42. Applications

43. Applications

44. Applications

45. Applications

46. References http://en.wikipedia.org/wiki/Digital-to-analog_converter Alciatore, “Introduction to Mechatronics and Measurement Systems,” McGraw-Hill, 2003 Horowitz and Hill, “The Art of Electronics,” Cambridge University Press, 2nd Ed. 1995 http://products.analog.com/products/info.asp?product=AD7224 http://courses.washington.edu/jbcallis/lectures/C464_Lec5_Sp-02.pdf http://www.eecg.toronto.edu/~kphang/ece1371/chap11_slides.pdf Past student lectures

47. Questions

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