PC/CP300 Electronics Laboratory II

Digital-to-Analog and Analog-to-Digital Converters Prelab

Interfacing between analog input devices and the typically digital processing environment, e.g. microprocessor or embedded system, requires analog input signals to be converted to digital signals for processing. The results of the processing then have to be converted to analog signals for controlling analog output transducers. These conversions are done by analog to digital (A/D) and digital to analog (D/A) converters, respectively.

For the digital-to-analog converters, DAC0800 and DAC1020, review the data sheets and answer the following questions for both chips.

• DAC0800 [PDF: 11 pages], a digital-to-analog converter from National Semiconductor
• DAC1020 [PDF: 14 pages], a digital-to-analog converter from National Semiconductor

1. What supply voltages are needed? What is the notation to denote the supply voltages?
   
   Can the (fixed) lab bench supplies be used for this purpose?
   
   
2. Is this a current output device or a voltage output device, i.e. is the output naturally a current or a voltage?
3. What type of reference (voltage or current) does the DAC require? How is this usually provided? What nominal value of reference is suggested? What range is allowed?
4. What is the input resolution (in bits) of the DAC? What are the related pins labeled? Indicate the most significant and least significant bits for these pins.
5. What is the range of output values?
6. What is the settling time for the DAC?
7. If the DAC can produce bipolar (i.e. positive and negative) output values, indicate the location and title of the sample circuit on the datasheet.
8. If the DAC can produce unipolar (e.g. positive) output values, indicate the location and title of the sample circuit on the datasheet.
9. Is the DAC double-buffered? How did you determine this?

For the analog-to-digital converters, ADC0804 and AD1380, review the data sheets and answer the following questions for both chips.

• ADC0804 [PDF: 41 pages], an analog-to-digital converter from National Semiconductor
• AD1380 [PDF; 8 pages], an analog-to-digital converter from Analog Devices

1. What supply voltages are needed? What is the notation to denote the supply voltages?
   
   Can the (fixed) lab bench supplies be used for this purpose?
   
   
2. Is this a current input device or a voltage input device, i.e. is the input naturally a current or a voltage?
3. What type of reference (voltage or current) does the ADC require? How is this usually provided? What nominal value of reference is suggested? What range is allowed?
4. What is the output resolution (in bits) of the ADC? What are the related pins labeled? Indicate the most significant and least significant bits for these pins.
5. What is the range of acceptable analog input values? What determines this range and how?
6. What is the maximum time required for a conversion?
7. How do you start a conversion?
8. How can you tell when a conversion is done?
9. How do you get the results of the conversion?
10. What (if any) initialization is needed?
11. If the ADC can be used with bipolar (i.e. positive and negative) inputs, indicate the location and title of the sample circuit in the datasheet.
12. Does the ADC have tri-state outputs? How did you determine this?

For both the DAC and the ADC, use a zener diode circuit with the appropriate diode for the reference voltage/current. For the zener diodes, LM336-2.5 and LM336-5.0, review the data sheets and answer the following questions for both devices.

• LM 336-2.5 [PDF: 12 pages], 2.5 V zener diode from National Semiconductor
• LM 336-5.0 [PDF: 11 pages], 5.0 V zener diode from National Semiconductor

1. Compare the two zener diodes in terms of reverse breakdown voltage and adjustment range.
2. Locate the provided typical application circuit examples for a reference voltage/current.
3. Almost all devices you have used until this point either have nondifferentiated axial leads or DIP packaging and the connection diagrams (pin out diagram) always show the top view of the component. The zener diodes come in DIP packages (which we will not be using) or as a device with differentiated axial leads (which we will be using). Does the datasheet use the top view for the connection diagrams? How did you determine this?