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op-amp en298 failure symptom determination technique half done

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on LM358
and datasheet added to related docs
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old_thesis/component_failure_modes_definition/component_failure_modes_definition.tex
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@ -158,6 +158,14 @@ and determine outcomes.
Different approval agenices may list different failure mode sets for the same generic components.
%%
%% DETAILED LOOK AT TWO COMPONENTS AND THEIR FAILURE MODES
%%
%% FROM TWO LITERATURE SOURCES, FMD-91 and EN298
%%
%%% THIS HAS BEEN TAKEN OUT AND PLACED IN THE C_GARRET OPAMPS DOCUMENT
\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
@ -187,7 +195,7 @@ For instance for {\textbf Resistor,~Fixed,~Film} we are given the following fail
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.
against symptoms of failure that the resistor could exhibit.
We can determine these symptoms and map these failure causes to three symptoms,
drift (resistance value changing), open and short.
@ -205,9 +213,15 @@ 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
EN298 ,the European gas burner safety standard,tends to be give more symptom centric failure modes than FMD-91,
and requires that a full FMEA be undertaken, examining all characterisic failure modes
of all components~\cite{en298}[11.2 5].
Annex A of EN298, gives failure modes for common components
and guidance on determing sets of failure modes for complex components (i.e. integrated circuits).
EN298~\cite{en298}[Annex A] (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
%
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
@ -240,8 +254,10 @@ $$ fm(R) = \{ OPEN, SHORT \} . $$
\subsubsection{FMD-91 Op-AMP Failure Modes}
%Literature suggests, latch up, latch down and oscillation.
FMD-91\cite{fmd91}{3-116] states,
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\%
@ -249,15 +265,58 @@ FMD-91\cite{fmd91}{3-116] states,
\item Opened $V_+$ open\%
\end{itemize}
These are internal causes of failure, more of interest to the component manufacter
than a designer looking for the symptoms of failure.
We need to translate these failure causes within the OP-AMP into symptoms.
We can look at each failure cause in turn.
\paragraph{OP-AMP failure cause: Poor Die attach}
The symptom for this is given as a low slew rate. This means that the op-amp
will not react quickly to changes on its input terminals.
This is a failure symptom that may not be of concern in a slow responding system like an
instrumentation amplifier. However, where higher frequencies are being processed
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
, 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, $LOW$, $HIGH$, $NOOP$.
\paragraph{Shorted $V_+$ to $V_-$}
Due to the high intrinsic gain of an op-amp, and the effect of offset currents
this will force the output HIGH or LOW.
We map this failure cause to $HIGH$ or $LOW$.
\paragraph{Open $V_+$}
This failure cause will mean that the minus input will have the very high gain
of the OP-AMP applied to it, and the output will be forced HIGH or LOW.
We map this failure cause to $HIGH$ or $LOW$.
\paragraph{Collecting failure symptoms from FMD-91}
We can define an OP-AMP, under FMD-91 definitions to have the following failure mode symptoms.
$$fm(OP-AMP) = \{ HIGH, LOW, NOOP, LOW_{slew} \} $$
EN298 does not specifically define OP\_AMPS failure modes; these would fall under the procedure outlined in
table \cite{en298}[A.1 note e].
EN298 does not specifically define OP\_AMPS failure modes; these can be determeined
by following a generic 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 single op-amp, say the $\mu741$ and examining
This technique cannot reveal failure symptoms that could be caused by internal
failures of the component under investigation. It will be interesting to compare the results we
get from this with the symptoms we derived from FMD-91 above.
We can examine these failure modes by taking a typical instrumentation op-amp, say the $LM358$~\cite{lm258} %\mu741$
and examining
these conditions.
\begin{figure}
\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}
\label{fig:lm258}
\end{figure}
%%

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@ -87,6 +87,8 @@ hierarchical failure mode model. Modularising FMEA should give benefits of reduc
allowing re-use of modules and reducing the number of by-hand analysis checks to consider.
\paragraph {Definitions}
\begin{itemize}
@ -96,6 +98,233 @@ allowing re-use of modules and reducing the number of by-hand analysis checks to
\item {\dc} - a new component derived from an analysed {\fg}
\end{itemize}
\subsection{A detailed look at failure symptoms of two components: 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}
The resistor is a ubiquitous component in electronics, and is there fore a good
example for examining it failure modes.
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
against symptoms of failure that the resistor could 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 ,the European gas burner safety standard,tends to be give more symptom centric failure modes than FMD-91,
and requires that a full FMEA be undertaken, examining all characterisic failure modes
of all components~\cite{en298}[11.2 5].
Annex A of EN298, gives failure modes for common components
and guidance on determing sets of failure modes for complex components (i.e. integrated circuits).
EN298~\cite{en298}[Annex A] (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
% \label{downrate}
% 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}
\subsubsection{FMD-91 Op-AMP Failure Modes}
%Literature suggests, latch up, latch down and oscillation.
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 Opened $V_+$ open\%
\end{itemize}
These are internal causes of failure, more of interest to the component manufacter
than a designer looking for the symptoms of failure.
We need to translate these failure causes within the OP-AMP into symptoms.
We can look at each failure cause in turn.
\paragraph{OP-AMP failure cause: Poor Die attach}
The symptom for this is given as a low slew rate. This means that the op-amp
will not react quickly to changes on its input terminals.
This is a failure symptom that may not be of concern in a slow responding system like an
instrumentation amplifier. However, where higher frequencies are being processed
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
, 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, $LOW$, $HIGH$, $NOOP$.
\paragraph{Shorted $V_+$ to $V_-$}
Due to the high intrinsic gain of an op-amp, and the effect of offset currents
this will force the output HIGH or LOW.
We map this failure cause to $HIGH$ or $LOW$.
\paragraph{Open $V_+$}
This failure cause will mean that the minus input will have the very high gain
of the OP-AMP applied to it, and the output will be forced HIGH or LOW.
We map this failure cause to $HIGH$ or $LOW$.
\paragraph{Collecting failure symptoms from FMD-91}
We can define an OP-AMP, under FMD-91 definitions to have the following failure mode symptoms.
$$fm(OP-AMP) = \{ HIGH, LOW, NOOP, LOW_{slew} \} $$
EN298 does not specifically define OP\_AMPS failure modes; these can be determeined
by following a generic procedure for integrated circuits outlined in
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$
and examining
these conditions.
\begin{figure}
\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}
\label{fig:lm258}
\end{figure}
\paragraph{EN298: Open and shorted pin failure symptom determination technique}
\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} \\
\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
FS7: PIN 1 OPEN & & $LOW$ & & $PDLow$ \\ \hline
FS8: PIN 1 OPEN & & $LOW$ & & $PDLow$ \\ \hline
FS2: R1 OPEN & & $HIGH$ & & $PDHigh$ \\ \hline
FS3: R2 SHORT & & $HIGH$ & & $PDHigh$ \\
FS4: R2 OPEN & & $LOW$ & & $PDLow$ \\ \hline
\hline
\end{tabular}
\label{tbl:pd}
\end{table}
%%
%% Paragraph using failure modes to build from bottom up
%%
\paragraph{ Creating a fault hierarchy.}
The main concept of FMMD is to build a hierarchy of failure behaviour from the {\bc}
level up to the top, or system level, with analysis stages between each
@ -112,7 +341,7 @@ A {\fg} is a collection of components that perform some simple task or function.
In order to determine how a {\fg} can fail,
we need to consider all failure modes of its components.
%
By analysing the fault behaviour of a `{\fg}' with respect to all its components failure modes,
By analysing the fault behavior of a `{\fg}' with respect to all its components failure modes,
we can determine its symptoms of failure.
%In fact we can call these
%the symptoms of failure for the {\fg}.
@ -755,7 +984,7 @@ For Functional Group 2 (FG2), let us map:
\section{Example Analysis: Non-Inverting OPAMP}
Consider a non inverting op-amp designed to amplify
a small positive voltage (typical use would be a thermocouple amplifier
taking a range from 0 to 25mV and amplifiying it to the useful range of an ADC, approx 0 to 4 volts).
taking a range from 0 to 25mV and amplifying it to the useful range of an ADC, approx 0 to 4 volts).
\begin{figure}[h+]