Browse Prior Art Database

Latch Circuit Insensitive to Disturb by Alpha Particles

IP.com Disclosure Number: IPCOM000049166D
Original Publication Date: 1982-May-01
Included in the Prior Art Database: 2005-Feb-09
Document File: 3 page(s) / 50K

Publishing Venue

IBM

Related People

Eardley, DB: AUTHOR

Abstract

This latch circuit contains additional redundant gates to achieve insensitivity to disturb by alpha particles.

This text was extracted from a PDF file.
At least one non-text object (such as an image or picture) has been suppressed.
This is the abbreviated version, containing approximately 53% of the total text.

Page 1 of 3

Latch Circuit Insensitive to Disturb by Alpha Particles

This latch circuit contains additional redundant gates to achieve insensitivity to disturb by alpha particles.

In the figure, the latch circuit includes a data entry gate (Tl... T5), a feedback gate (T6...T10) and an inverter gate (T11...T14). The latch is made insensitive to disturb signals from alpha particles by the addition of redundant gates (T15...T19 and T20...T23).

During the data retention period, C is high and C is low. If the latch output is high, then T7 and T16 are on. The emitter dot of T4, T9 and T19 is low. T11 and T20 are off. The emitter dot of T13 and T22 provides the output which is high. In some applications, this state must be maintained for a large number of machine cycles (Approximately 100000) without disturb. If, during this period, an alpha particle passes through the subcollector-substrate depletion region of T11, the resulting ionization will cause transient leakage from subcollector to substrate. The collector of T11 will fall and then recover towards the positive power supply voltage (typically +1.25 V). During the negative excursion of the T11 collector, T13 will be turned off. While T13 is off, T22 will hold the latch up at the high level and latch data will not be disturbed.

If an alpha particle passes through the subcollector-substrate depletion region of T20, then T13 will hold the latch up at the high level. Only if both T20 and T11 collectors have negative excursions with overlapping pulse widths will the latch output be permitted to fall. The pulse width of the negative excursion is determined by the RC time constant at the collector node. Thus, overlapping negative pulses could be caused by two alpha particle strikes spaced apart in...