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# Current Switch With Dynamic Logic Swings

IP.com Disclosure Number: IPCOM000035954D
Original Publication Date: 1989-Aug-01
Included in the Prior Art Database: 2005-Jan-28
Document File: 4 page(s) / 114K

IBM

Wong, RC: AUTHOR

## Abstract

Conventional logic gates switch between a fixed set of two voltage levels, which represent the TRUE and FALSE state of a Boolean function. In Cascode current switches, multiple sets of voltage levels are used. However, each individual signal operates only in one set. (Image Omitted)

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Current Switch With Dynamic Logic Swings

Conventional logic gates switch between a fixed set of two voltage levels, which represent the TRUE and FALSE state of a Boolean function. In Cascode current switches, multiple sets of voltage levels are used. However, each individual signal operates only in one set.

(Image Omitted)

A new current switch is proposed, where the signal voltage levels can be dynamically shifted among multiple sets of logic swings. This dynamic swing shift is to provide a gating function without using the gating devices. Thus delay and circuit can be reduced.

Fig. 1 illustrates this swing shift scheme in the implementation of a trigger latch. Assume RC=2*RS and J=JS, then the two sets of logic levels for the latches are: VH(1) & VH(0) for the high voltage swing, and

VH(1) & VL(0) for the low voltage swing.

(Image Omitted)

These voltage levels are related as

follows:

VH(1)-VH(0) = VL(1)-VL(0) = 2*(VH(1)-VL(1)) =

2*(VH(0)-VL(0))

The trigger signal T switches only between VL(1) & VL(0). When T is up, L1 & -- switch between VL(1) & VL(0) and L2 & -- switch between VL(1) & VL(0) Thus, the L1 datum is simply passed onto L2. The main advantages of this scheme are:
(1) Circuits are simpler since no gating devices are used.
(2) Circuits are faster than conventional current switches

since the gating logic stage is omitted.
(3) Power dissipation is less than those of the cascode

current switches since the power supply voltage span

from VCC to VEE is small...