Notice: Do not discuss the content of this assignment with any student who is not taking module ES3B2.
ES3A3 – Analogue Systems Design
Assignment - this represents 5% of module credit or 0.75 Credits.
It concerns the worst-case design analysis of a given circuit.
This document is dated Wednesday 22nd October 2014
Written by Dr. David C. Dyer
Below is the description of what you are expected to do for the first assignment which is part of ES3A3. Submission is Thursday of week 9 in *.pdf format only. (format to be confirmed)
The analysis should be presented in a succinct written report of at most 6 sides of A4 in a font no smaller than 11 point. This should bear your student ID code with numbered pages. All references used should be cited.
The circuit below generates a ‘square-wave’ (of duty cycle D) on test land Z346 that is used by a ‘buck’ converter to switch –V_BATT (-70 V) to a resistive load. Consequently, the mean voltage across the load is somewhere between 0 and -70 V depending on the relative proportion of the high and low phases of the
Furthermore, the supplier of IC32 is not defined and the hysteresis of the Schmitt trigger at pin 1 will depend on exactly who’s part is fitted. See http://www.datasheetcatalog.com/ or elsewhere for data from 3 independent manufactures. Similarly for IC21.
You may assume that the capacitors have ±% tolerance shown but do not vary with applied voltage.
File: WAR-ES3A3-A01-20141022.docx 1 of 2 Copyright © 2014 David C. Dyer
You are to determine
1. The minimum and maximum frequencies that will be encountered at pin 3 of IC21.
2. The minimum and maximum Duty cycle at pin 13 of IC21 and hence the least negative and most negative voltages when placed on a scale of -70 V.
3. The worst case voltage deviations from the mean values across all variations of all parts.
4. The supplier(s) who’s integrated circuits will give the least deviation.
You are expected to develop an equation for the operating frequency of the Schmitt Trigger oscillator and with careful attention to the pulse widths of the high and low phases explain the precise behaviour of the monostable circuit built around IC21. Be careful to interpret carefully the truth tables associated with IC21.
Having developed the appropriate formula you may use a spreadsheet to perform calculations. However, if this is included within the repot be sure to explain the way each cell is calculated.
Also, state the questions and present the analysis in a way that it will have meaning to any future reader.
File: WAR-ES3A3-A01-20141022.docx 2 of 2 Copyright © 2014 David C. Dyer