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Latch for Coupling Power Supply Line to Utilization Circuits

IP.com Disclosure Number: IPCOM000079301D
Original Publication Date: 1973-Jun-01
Included in the Prior Art Database: 2005-Feb-26
Document File: 2 page(s) / 31K

Publishing Venue

IBM

Related People

Clark, MJ: AUTHOR

Abstract

The need constantly arises in power supply systems for a reliable electronic latch that is not sensitive to line noise, or inductive kickback spikes that are imposed through regulators and on DC voltage levels. The figure shows such a latch 1 including +AND circuits 2 and 7, +OR circuit 3, and a feedback circuit including the light-emitting diode 4, the photosensitive Darlington pair 5, and the inverter 6. Positive logic signals at the inputs of 2 set the latch, i.e., produce a positive output from 2, which produces a positive output from 3 to energize 4 (and output line 8). Light emitted from 4 impinges on the base of transistor 5a to turn on 5. This turns 6 off to apply a positive hold signal to 7. The line, -RESET, is normally positive, thus maintaining 1 in its set state.

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Latch for Coupling Power Supply Line to Utilization Circuits

The need constantly arises in power supply systems for a reliable electronic latch that is not sensitive to line noise, or inductive kickback spikes that are imposed through regulators and on DC voltage levels. The figure shows such a latch 1 including +AND circuits 2 and 7, +OR circuit 3, and a feedback circuit including the light-emitting diode 4, the photosensitive Darlington pair 5, and the inverter 6. Positive logic signals at the inputs of 2 set the latch, i.e., produce a positive output from 2, which produces a positive output from 3 to energize 4 (and output line 8). Light emitted from 4 impinges on the base of transistor 5a to turn on 5. This turns 6 off to apply a positive hold signal to 7. The line, -RESET, is normally positive, thus maintaining 1 in its set state. The +AND circuit 7 normally maintains the latch in its set state until -RESET goes negative.

The diode 4 is selected with desired delay characteristics, such that the feedback signal from the output of 3 (during setting of 1) is propagated to the input of 7 fast enough to permit the operation of 1 at its desired speed. However, the turn-off delay of 4 (to decrease its light intensity so as to deactivate the base region of 5a to turn off the Darlington pair 5) is selected to be of long enough duration, to be insensitive to the power supply line noise and inductive kickback on line 8. Thus line noise will not erroneously reset 1.

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