David W Mccall

US Patent:

51343126, Jul 28, 1992

Filed:

Apr 25, 1991

Appl. No.:

7/691454

Inventors:

Frederick J. Jones - Leominister MA
David L. McCall - Medway MA
John H. Hackenberg - Northboro MA

Assignee:

Digital Equipment Corporation - Maynard MA

International Classification:

H03K 3289
H03K 19086

US Classification:

3072722

Abstract:

A bipolar ECL latch or flip-flop circuit of the isolated differential feedback type provides a high level of alpha particle immunity, without unduly affecting the propagation delay, power dissipation or circuit area in an integrated circuit device. A pair of latch transistors having differential input are used, with common emitters coupled to a clocked current source. The latch outputs are coupled back to a pair of holding transistors by two emitter follower feedback transistors. The holding transistors have a common emitter connection to a current source clocked inversely to that of the current source for the latch transistors, so the state of the latch is held by the holding transistors. The amplification of the feedback transistors is reduced so that the speed with which the transistor can react to transient noise such as that produced by an alpha hit is reduced. A shared current source is employed for the emitter follower feedback transistors to reduce the alpha particle sensitivity by lowering the feedback current without requiring two larger resistor values.