Re-writing the resistor and op-amp failure mode definitions

old_thesis/component_failure_modes_definition/component_failure_modes_definition.tex

@@ -144,41 +144,119 @@ When building from the bottom up, it is more meaningful to call them `derived~co
  
 
 
-\section{Failure Modes in depth: A detailed look at the op-amp and the resistor}
+\section{Failure Modes in depth}
+
+For FMEA appraisals of systems we begin with components. 
+%These will have a set of failure modes assigned to them.
+In order to perform FMEA we require a set of failure modes for each component in the system under investigation.
+These are failure modes from the perspective of the user
+of the component. We are not usually concerned with how the component has failed
+internally. What we need to know are the symptoms of failure.
+With these symptoms, we can trace their effects through the system under investigation
+and determine outcomes.
+
+Different approval agenices may list different failure mode sets for the same generic components.
+
+ 
+\subsection{A detailed look at the op-amp and the resistor}
 
 We look in detail at two common electrical components in this section and examine how
 two sources of information on failure modes view their failure mode behaviour.
 We look at the reasons why some known failure modes are omitted, or presented in 
 specific but unintuitive ways.
+%We compare the US. military published failure mode specifications wi
+
 
 - Failure modes. Prescribed failure modes EN298 - FMD91
 
 \subsection{resistor}
 
-EN298 says......
+The resistor is a ubiquitous component in electronics, and is there fore a good
-Parameter change not considered for EN298 because the resistors are down-rated from
+example for examining it failure modes.
-maximum possible voltage exposure -- find refs.
+FMD-91\cite{fmd91}[3-178] lists many types of resistor
+and lists many possible failure causes.
+For instance for {\textbf Resistor,~Fixed,~Film} we are given the following failure causes:
+\begin{itemize}
+ \item Opened 52\%  
+  \item Drift 31.8\%  
+ \item Film Imperfections 5.1\%  
+ \item Substrate defects 5.1\% 
+ \item Shorted 3.9\%  
+ \item Lead damage 1.9\%  
+\end{itemize}
+This information may be of insterest to the manufacturer of resistors, but it does not directly
+help a circuit designer.
+The circuit designer is not interested in the causes of resistor failure, but to build in contingecy
+the symptoms of failure that the resistor may exhibit.
+We can determine these symptoms and map these failure causes to three symptoms,
+drift (resistance value changing), open and short.
+
+\begin{itemize}
+ \item Opened 52\% $\mapsto$ OPENED
+  \item Drift 31.8\% $\mapsto$ DRIFT
+ \item Film Imperfections 5.1\% $\mapsto$ OPEN
+ \item Substrate defects 5.1\% $\mapsto$ OPEN
+ \item Shorted 3.9\% $\mapsto$  SHORT
+ \item Lead damage 1.9\% $\mapsto$ OPEN
+\end{itemize}
+The main causes of drift are overloading of components.
+This is bourne out in entry for a resistor network where the failure
+modes do not include drift.
+If we can ensure that our resistors will not be exposed to overload conditions, drift or parameter change
+can be reasonably excluded.
+
+EN298~\cite{en298}[Annex A], the gas burner safety standard, for most types of resistor
+only requires that the failure mode OPEN be considered in FMEA analysis.
+for resitor types not specifically listed in EN298, the failure modes
+are considered to be either OPEN or SHORT.
+The reason that parameter change is not considered for resistors chosen for an EN298 compliant system; is that they must be must be {\em downrated},
+that is to say the power and voltage ratings of components must be calculated
+for maximum possible exposure, with a 40\% margin of error. This ensures the resistors will not be overloaded.
+
+% XXXXXX get ref from colin T
+
+%If a resistor was rated for instance for  
+
+%These are useful for resistor manufacturersthey have three failure modes
+%EN298 
+%Parameter change not considered for EN298 because the resistors are down-rated from
+%maximum possible voltage exposure -- find refs.
 
 
-FMD-91 gives the following percentages for failure rates in
+% FMD-91 gives the following percentages for failure rates in
-\label{downrate}
+% \label{downrate}
-The parameter change, is usually a failure mode associated with over stressing the component.
+% The parameter change, is usually a failure mode associated with over stressing the component.
 In a system designed to typical safety critical constraints (as in EN298)
 these environmentally induced failure modes need not be considered.
 
+
+For this study we will take the conservative view from EN298, and consider the failure
+modes for a resistor to be OPEN and SHORT.
+i.e.
+
+$$ fm(R) = \{ OPEN, SHORT \} . $$
+
 \subsection{op-amp}
 
-Literature suggests, latch up, latch down and oscillation.
+
-FMD-91 states, V+ disconnected, V- V+ shorted, NOOP and Low slew.
+
+%Literature suggests, latch up, latch down and oscillation.
+FMD-91\cite{fmd91}{3-116] states,
+\begin{itemize}
+ \item Degraded Output 50\% Low Slew rate - poor die attach
+  \item No Operation - overstress 31.3\%  
+ \item Shorted $V_+$ to $V_-$, overstress, resistive short in amplifier\%  
+ \item Opened $V_+$ open\%  
+\end{itemize}
+
+
+
 
 EN298 does not specifically define  OP\_AMPS failure modes; these would fall under the procedure outlined in
 table \cite{en298}[A.1 note e].
 This demands that all open connections, and shorts between adjacent pins be considered.
-We can examine these failure modes by taking our 358 op-amp and examining
+We can examine these failure modes by taking a typical single op-amp, say the $\mu741$  and examining
-
+these conditions.
-
- looking at
-Discuss why. Determine more user friendly terms from FMD91 definition.
 
 
 
@@ -186,6 +264,19 @@ Discuss why. Determine more user friendly terms from FMD91 definition.
 %% Paragraph using failure modes to build from bottom up
 %%
 
+
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+
 \section{Fault Mode Analysis, top down or bottom up?}
 
 Traditional static fault analysis methods work from the top down.

old_thesis/logic_diagram/paper.tex~

@@ -1,42 +0,0 @@
-
-\documentclass[a4paper,10pt]{article}
-\usepackage{graphicx}
-\usepackage{fancyhdr}
-\usepackage{tikz}
-\usetikzlibrary{shapes,snakes}
-\usepackage{amsfonts,amsmath,amsthm}
-\input{../style}
-\usepackage{ifthen}
-\usepackage{lastpage}
-
-\newboolean{paper}
-\setboolean{paper}{true} % boolvar=true or false
-
-%\newtheorem{definition}{Definition:}
-
-\begin{document}
-\pagestyle{fancy}                                                                                                                                                                                                                                 
-\fancyhf{}                                                                                                                                                                                                                                        
-%\renewcommand{\chaptermark}[1]{\markboth{ \emph{#1}}{}}                                                                                                                                                                                          
-\fancyhead[LO]{}                                                                                                                                                                                                                                  
-\fancyhead[RE]{\leftmark}                                                                                                                                                                                                                         
-%\fancyfoot[LE,RO]{\thepage}                                                                                                                                                                                                                      
-\cfoot{Page \thepage\ of \pageref{LastPage}}                                                                                                                                                                                                      
-\rfoot{\today}                                                                                                                                                                                                                                    
-\lhead{Propositional Logic Diagram FMMD}  
-
-                                              % numbers at outer edges
-\pagenumbering{arabic}                        % Arabic page numbers hereafter
-\author{R.P.Clark}
-\title{Propositional Logic Diagrams}
-\maketitle 
-\input{logic_diagram_paper}
-
-\bibliographystyle{plain}
-\bibliography{../mybib,../vmgbibliography}
-
-%\begin{verbatim}
-%$Id: paper.tex,v 1.4 2009/11/28 20:05:52 robin Exp $
-%\end{verbatim}
-
-\end{document}