1. ECE-L304 Lecture 3

2. 9/13/2018
Important Notes
Only positive voltages can be applied to ADC, check input signal on oscilloscope before applying to circuit
Control pins of ADC must be wired for the circuit to begin operation, if LEDs do not light check control pins
Read Data sheet before lab to see how internal clock rate relates to sampling rate
After some wiring is done, you concentrate on what timing components to use, how to characterize what is observed on the LED array, and how to measure the data on the test port.
ECE-L304 Lecture 3

3. Questions What is the frequency bandwidth of human speech?
9/13/2018
Questions
What is the frequency bandwidth of human speech?
What is the minimum sampling rate for digital recording of speech?
How many internal clock cycles does this ADC need to take one sample?
What is the maximum internal clock rate?
What clock rate to you want? Defend this choice. What values of R and C give you this rate?
A good report will answer all of these questions in one form or another.
The resistor and capacitor included in your kit will produce a functional circuit, but not one that is optimized for speech.
ECE-L304 Lecture 3

4. Floorplan RAM DAC ADC ADC Out LED Resistor Address inputs AD/RAM
Controls
LED
ECE-L304 Lecture 3

5. Step 2 Deliverables ADC Performance Measurements
Floorplan/RC calculations, results and explanation
Table of dc tests, with reverse calculations and analysis
Observation of performance on logic analyzer
Comparison of predicted and measured timing
Intr and Internal clock signals
Report writing in progress
Due next week
Circuit must be checked and tested by Kongkuo or myself before moving on to step 3
ECE-L304 Lecture 3

6. DC Testing Purpose How? Test functionality of ADC design
Apply dc voltage
Record in notebook:
Applied voltage
Pattern of LED display
High/low or dark/light
Power supply voltage
ECE-L304 Lecture 3

7. Table of Measurements ECE-L304 Lecture 3 9/13/2018
Only two decimal place are available from the power supply. The multimeter can be used for more accuracy.
ECE-L304 Lecture 3

8. Calculations
Use the equation in your lab notes to back-calculate the dc input voltage from the LED status, add this result to your table, and comment on accuracy
Use your data to find the voltage resolution of your system
ECE-L304 Lecture 3

9. Calculations
ECE-L304 Lecture 3

10. Observe Data Bus
Replace your dc input source with a function generator
Voltage ramp output, V
Very low frequency 0.1 to 10 Hz
Observe the progression of the binary count on the display
ECE-L304 Lecture 3

11. Observe the ADC Output Observe data bus
Add probes to pins 4 & 5 of ADC
Pin 4 is the internal clock
Pin 5 pulses every time the ADC completes a conversion
Use these times to determine the period of the internal clock
Check this result against your initial design goal
ECE-L304 Lecture 3