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Forum: Reliability & Maintainability Questions and Answers

Topic: Reliability & Maintainability Questions and Answers

Topic Posted by: Reliability & Maintainability Forum (src_forum@alionscience.com )
Organization: System Reliability Center
Date Posted: Mon Aug 31 12:47:36 US/Eastern 1998

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Original Message:

Posted by: Rushabh J (rushabh.jariwala@gmail.com )
Date posted: Wed Mar 30 8:26:11 US/Eastern 2005
Subject: How to estimate IC Failure Rate in IDLE Mode
Message:
I am trying to predict the reliability of electronics control. The control is programmed such a way that 5 ICs would be active every 0.5 Sec. for 0.0012 Sec. and then it would go to it's sleep mode or idle mode. Main point is we are not switching it off but just keeping it in IDLE / SLEEP mode. For all this ICs I got the failure rate data in the working condition of IC. We got the Reliability Test Report conducted for 1000 Hrs. I tried in RELEX as well as PRISM to find any option which takes care of standby/IDLE/Sleep mode failure rates, but it gives option to enter the mission profile time against different temperature. But I believe entering different temperature is not the solution . Because Ideally in stand by more failrue rate would change. My question is how to calculate the total Reliability. In the IDLE/Sleep mode time what should we consider the failure rate. Thanking in Anticipation.


Reply:

Subject: Quiescent or Sleep Failure Modes
Reply Posted by: bwd (b )
Organization: RAC
Date Posted: Thu Mar 31 10:39:48 US/Eastern 2005
Message:
Quiescent or Sleep Failure Mode Calculating the reliability for the entire life of an item is a difficult problem. The RAC PRISM model for electronic components has the capability to provide assessments for the components for operating, non-operating and cycling conditions. Your problems is the addition of a quiescent or sleep mode which is neither operating nor non-operating. My suggestion is to establish failure rates for the operating condition and the non-operating condition using the PRISM model for the components. The PRISM reliability models are built on the inclusion of all failure modes for a device which includes both operating and non-operating stresses. Quiescent failure modes should be subset of reduced operating modes. These failure rates will then be the range of possibilities for the quiescent failure rate. I would then assume a uniform distribution as insufficient data are available to use another. From this uniform distribution, I would determine the 50% point and use this value as the estimated quiescent failure rate. The life reliability can then be calculated using the three failure rate values, operating, non-operating and quiescent, and the time spent in each condition.


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