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OK think I got more of the componen failure mode stuff

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done...
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Your Name 2012-03-12 20:08:02 +00:00
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thesis_submission/CH5_Examples/copy.tex
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@ -12,6 +12,8 @@
\usepackage{lastpage}
\newcommand{\fg}{\em functional~group}
\newcommand{\fm}{\em failure mode}
\newcommand{\fms}{\em failure modes}
\newcommand{\fgs}{\em functional~groups}
\newcommand{\dc}{\em derived~component}
\newcommand{\dcs}{\em derived~components}
@ -93,6 +95,7 @@ allowing re-use of modules and reducing the number of by-hand analysis checks to
\begin{itemize}
\item {\bc} - is taken to mean a `part' as defined above~\cite{scse}[p.619]. We should be able to define a set of failure modes for every {\bc}.
\item {\fm} - failure mode - the ways in which a component can fail
\item {\fg} - a collection of components chosen to perform a particular task
\item {\em symptom} - a failure mode of a functional group caused by one or more of its component failure modes.
\item {\dc} - a new component derived from an analysed {\fg}
@ -102,14 +105,53 @@ allowing re-use of modules and reducing the number of by-hand analysis checks to
\subsection{A detailed look at failure symptoms of two components: the op-amp and the resistor}
In order to apply any form of Failure Mode Effects Analysis (FMEA) we need to know the ways in which the components we are using can fail.
How base components could fail internally, its not of interest to an FMEA investigation.
The FMEA investigator needs to know what failure behaviour a component may exhibit, or in other words, its
modes of failure.
A large body of literature exists which gives guidance for for determining component {\fms}.
For this study FMD-91~\cite{fmd91} and the gas burner standard EN298~\cite{en298}.
%Some standards prescribe specific failure modes for generic component types.
In EN298 failure modes for generic component types are prescribed, or
determined by a procedure where failure scenarios of all pins OPEN and all adjacent pins shorted
are examined.
%
FMD-91 is a reference document released into the public domain by the United States DOD
and describes {\fms} of common electronic components.
FMD-91 entries include descriptions of internal failures along with {\fms}.
FMD-91 entries need, in some cases, some interpretation to be mapped to a clear set of
component failure modes.
% One is from the US military document FMD-91, where internal failures
% of components are described (with stats).
%
% The other is EN298 where the failure modes for generic component types are prescribed, or
% determined by a procedure where failure scenarios of all pins OPEN and all adjacent pins shorted
% is applied. These techniques
%
% The FMD-91 entries need, in some cases, some interpretation to be mapped to
% component failure symptoms, but include failure modes that can be due to internal failures.
% The EN298 SHORT/OPEN procedure cannot determine failures due to internal causes but can be applied to any IC.
%
% Could I come in and see you Chris to quickly discuss these.
%
% I hope to have chapter 5 finished by the end of March, chapter 5 being the
% electronics examples for the FMMD methodology.
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
We then compare and contrast the failure modes determined for these components
from the FMD-91 reference source and from the guidelines of the
European burner standard EN298.
- Failure modes. Prescribed failure modes EN298 - FMD91
%- Failure modes. Prescribed failure modes EN298 - FMD91
\subsection{resistor}
@ -186,7 +228,11 @@ $$ fm(R) = \{ OPEN, SHORT \} . $$
\subsection{op-amp}
The op-amp is a differential amplifier and is very widely used.
They are typically packaged in dual or quad configurations---meaning
that a chip will typically contain two or four amplifiers.
For the purpose of example, we look at
a typical op-amp designed for instrumentation and measurement, the dual packaged version of the LM358~\cite{lm358}.
\subsubsection{FMD-91 Op-AMP Failure Modes}
@ -194,8 +240,7 @@ $$ fm(R) = \{ OPEN, SHORT \} . $$
For OP-AMP failures modes, 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 No Operation - overstress 31.3\% \item Shorted $V_+$ to $V_-$, overstress, resistive short in amplifier\%
\item Opened $V_+$ open\%
\end{itemize}
@ -213,7 +258,7 @@ a signal may be lost.
We can map this failure cause to a failure symptom, and we can call it $LOW_{slew}$.
\paragraph{No Operation - over stress}
Here the OP_AMP has been damaged, and the output may be held HIGH LOW, or may be effectively tri-stated
Here the OP\_AMP has been damaged, and the output may be held HIGH LOW, or may be effectively tri-stated
, i.e. not able to drive circuitry in along the next stages of te signal path: we can call theis state NOOP (no Operation).
We can map this failure cause to three symptoms, $LOW$, $HIGH$, $NOOP$.
@ -233,8 +278,8 @@ We can define an OP-AMP, under FMD-91 definitions to have the following failure
$$fm(OP-AMP) = \{ HIGH, LOW, NOOP, LOW_{slew} \} $$
EN298 does not specifically define OP\_AMPS failure modes; these can be determeined
by following a generic procedure for integrated circuits outlined in
EN298 does not specifically define OP\_AMPS failure modes; these can be determined
by following a procedure for `integrated~circuits' outlined in
annex~A~\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 a typical instrumentation op-amp, say the $LM358$ %\mu741$
@ -245,7 +290,7 @@ these conditions.
\centering
\includegraphics[width=200pt]{./lm258pinout.jpg}
% lm258pinout.jpg: 478x348 pixel, 96dpi, 12.65x9.21 cm, bb=0 0 359 261
\caption{Pinout for an LM258 dual OP-AMP}
\caption{Pinout for an LM358 dual OP-AMP}
\label{fig:lm258}
\end{figure}
@ -260,31 +305,51 @@ these conditions.
\begin{table}[h+]
\caption{LM358: EN298 Single failure symptom extraction}
\begin{tabular}{|| l | l | c | c | l ||} \hline
\textbf{Failure Scenario} & & \textbf{Pot Div Effect} & & \textbf{Symptom} \\
\textbf{Failure Scenario} & & \textbf{Amplifier Effect} & & \textbf{Symptom(s)} \\
\hline
FS1: PIN 1 OPEN & & $LOW$ & & $PDLow$ \\ \hline
FS2: PIN 1 OPEN & & $LOW$ & & $PDLow$ \\ \hline
FS3: PIN 1 OPEN & & $LOW$ & & $PDLow$ \\ \hline
FS4: PIN 1 OPEN & & $LOW$ & & $PDLow$ \\ \hline
FS5: PIN 1 OPEN & & $LOW$ & & $PDLow$ \\ \hline
FS6: PIN 1 OPEN & & $LOW$ & & $PDLow$ \\ \hline
& & & & \\ \hline
FS7: PIN 1 OPEN & & $LOW$ & & $PDLow$ \\ \hline
FS8: PIN 1 OPEN & & $LOW$ & & $PDLow$ \\ \hline
FS1: PIN 1 OPEN & & A output open & & $NOOP_A$ \\ \hline
FS2: PIN 2 OPEN & & A-input disconnected, & & \\
& & infinite gain on A+input & & $LOW_A$ or $HIGH_A$ \\ \hline
FS3: PIN 3 OPEN & & A+input disconnected, & & \\
& & infinite gain on A-input & & $LOW_A$ or $HIGH_A$ \\ \hline
FS4: PIN 4 OPEN & & power to chip (ground) disconnected & & $NOOP_A$ and $NOOP_B$ \\ \hline
FS2: R1 OPEN & & $HIGH$ & & $PDHigh$ \\ \hline
FS5: PIN 5 OPEN & & B+input disconnected, & & \\
& & infinite gain on B-input & & $LOW_B$ or $HIGH_B$ \\ \hline
FS6: PIN 6 OPEN & & B-input disconnected, & & \\
FS6: PIN 6 OPEN & & infinite gain on B+input & & $LOW_B$ or $HIGH_B$ \\ \hline
FS7: PIN 7 OPEN & & B output open & & $NOOP_B$ \\ \hline
FS8: PIN 8 OPEN & & power to chip & & \\
FS8: PIN 8 OPEN & & (Vcc) disconnected & & $NOOP_A$ and $NOOP_B$ \\ \hline
& & & & \\
& & & & \\
& & & & \\ \hline
FS9: PIN 1 $\stackrel{short}{\longrightarrow}$ PIN 2 & & A -ve 100\% Feed back, low gain & & $LOW_A$ \\ \hline
FS3: R2 SHORT & & $HIGH$ & & $PDHigh$ \\
FS4: R2 OPEN & & $LOW$ & & $PDLow$ \\ \hline
FS10: PIN 2 $\stackrel{short}{\longrightarrow}$ PIN 3 & & A inputs shorted, & & \\
& & output controlled by internal offset & & $LOW_A$ or $HIGH_A$ \\ \hline
FS11: PIN 3 $\stackrel{short}{\longrightarrow}$ PIN 4 & & A + input held to ground & & $LOW_A$ \\ \hline
FS12: PIN 5 $\stackrel{short}{\longrightarrow}$ PIN 6 & & B inputs shorted, & & \\
& & output controlled by internal offset & & $LOW_B$ or $HIGH_B$ \\ \hline
FS13: PIN 6 $\stackrel{short}{\longrightarrow}$ PIN 7 & & B -ve 100\% Feed back, low gain & & $LOW_B$ \\ \hline
FS14: PIN 7 $\stackrel{short}{\longrightarrow}$ PIN 8 & & B output held high & & $HIGH_B$ \\ \hline
\hline
@ -293,19 +358,40 @@ these conditions.
\end{table}
\clearpage
\subsection{Comparing the component failure mode sources}
EN298 pinouts failure mode technique.
For our OP-AMP example could have come up with different symptoms for both sides. Cannot predict the effect of internal errors, for instance ($LOW_{slew}$)
is missing from the EN298 failure modes set.
% FMD-91
%
% I have been working on two examples of determining failure modes of components.
% One is from the US military document FMD-91, where internal failures
% of components are described (with stats).
%
% The other is EN298 where the failure modes for generic component types are prescribed, or
% determined by a procedure where failure scenarios of all pins OPEN and all adjacent pins shorted
% is applied. These techniques
%
% The FMD-91 entries need, in some cases, some interpretation to be mapped to
% component failure symptoms, but include failure modes that can be due to internal failures.
% The EN298 SHORT/OPEN procedure cannot determine failures due to internal causes but can be applied to any IC.
%
% Could I come in and see you Chris to quickly discuss these.
%
% I hope to have chapter 5 finished by the end of March, chapter 5 being the
% electronics examples for the FMMD methodology.
\clearpage
%%