CHAPTER 5 MEASUREMENT CONSIDERATIONS
5.3 T EST F LOW
5.3.2 Test Flow of Binary Input
If we do not have 4-PAM source, there is an alternative way to replace 4-PAM with binary signal. First, it is fed with a PRBS which represents the lowest eye of 4-PAM signal while switching to calibration mode. After a period of calibration, we will get the selected channel number of the level. Record it and repeat the same procedure for the rest levels.
Second, we switch to normal mode when complete calibration is done, and feed the lowest binary sequence again and scan channels. It tells which channel is the best either by BER analysis or eye-diagram comparison. Last, we check the other two levels iteratively. The test flow is shown in Figure 5.8.
BEGIN
increment &
Record
Figure 5.8 Test flow of binary input
Chapter 6 Conclusion
In this thesis, we have proposed an ADC with advantages of simple structure, high-speed, power-efficient, low hardware overhead, and immunity against process variation and temperature. We use tri-state inverters as comparator and building up multiplexers for the merit of power saving and gain and gain boosting. By proper overlap between comparators and multiplexers, we can enhance the accuracy of conversion. Because the threshold comparators are deeply impacted by process variation, we use an undersampling scheme for calibration. By means of duty cycle estimation, we can choose optimal comparators and channels for conversion. The numbers of sampling are evaluated by statistical analysis. For example, we can get 99.35% confidence level for a 300mV peak to peak input out of a 7-bit counter to acquire the best channels.
In verification, we propose PRBS and 4-PAM test. PRBS is a simpler way for data acquisition, but the test flow is more complicated for the three-eye iteration. As for 4-PAM source, we have on-chip and off-chip solutions. On-chip signal solution is a self-generating signal by LFSR and DAC. On the other hand, off-chip solution is configured as a resistor-ladder type DAC through a high slew rate analog MUX.
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Autobiography
I was born in Taichung and raised in a traditional family. After graduating from National Central University, I went to military service as a lieutenant officer. I had learned responsibility and led staffs to achieve missions.
My first job was a hardware engineer, developing switch hubs. Later I went on to devote myself to semiconductor field as a product engineer, dealing with yield improvement and new product verification. Being aggressive by nature, I had achieved some goals that other people could not. For instance, I was the youngest qualified statistical process control seed, and quality innovation team leader. Needless to say, team work spirit is important. I have cooperated with others to solve problems, such as shooting defective sources with integration staffs, and working out the returned parts with quality assurance staffs. I also applied Taguchi method and statistical analysis to improve product and testing quality.
Years later, I went back to campus for advance study, majoring in electric engineering and concentrating on integrated circuits design. My project is to make a 2.5Gsps self-calibrating 4-PAM receiver, and evaluate the accuracy by statistical method. During these years, I do appreciate my professor directs me both philosophy and profession. There goes an old saying: “No pain, no gain!” I will devote to work enthusiastically and extend my width and depth aggressively.