The results of cosmic rays had been as soon as mentioned in “Doubled-up MOSFETs“.
The thought was that part redundancy, paired MOSFETs in that case, would permit one MOSFET to nonetheless operate even when its companion in a switched mode energy provide had been to be disabled from regular switching due to a cosmic ray occasion, a single occasion upset, or an SEU (Determine 1).
Determine 1 An SEU from a cosmic ray can result in part failure.
Nevertheless, an SEU doesn’t essentially have to come back from a cosmic ray. CMOS built-in circuits are generally seen to latch-up for no obvious motive. The latch-up occasion comes about from inner four-layer constructions that look very very similar to SCRs which when triggered, can nearly brief circuit the +Vcc rail pin to floor. In contrast to the facility MOSFET scenario, part redundancy might not be attainable. In such a case, SEU restoration often is the reply.
Determine 2 is conceptual, however it’s derived from precise circuitry that was utilized in a extra complicated design.Â
Determine 2 The SEU restoration idea the place the circuitry in inexperienced in latch-up susceptible.
The essential concept is that Q1, Q2 etal in inexperienced represents a latch-up susceptible built-in circuit, in all probability CMOS, whereas V1 etal in blue represents a latch-up set off. An RC pair in yellow supplies a delay of the latch-up restoration course of in order that the restoration situation will be extra simply seen on the scope, however we are going to shortly take away that RC pair.
When the IC latches up, it drags down the output of the +5-volt regulator. When that voltage falls under the comparator threshold, +3 volts as proven right here, the comparator sends a drive pulse to the facility MOSFET which additional lowers the rail voltage to the place the IC latch can’t be sustained. When the facility MOSFET turns off once more, the +5-volt regulator output voltage returns to regular.
If we now take away that RC delay, the situation proceeds the identical method, however on this simulation all of it occurs too quick for the saturation voltage of the latched-up machine to be viewable within the scope show (Determine 3).
Determine 3 SEU Restoration the place the RC delay is now eliminated.
John Dunn is an electronics advisor, and a graduate of The Polytechnic Institute of Brooklyn (BSEE) and of New York College (MSEE).
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