Browse Prior Art Database

CIRCUIT OF PREVENTING COUPLING NOISE AND NOISE SPIKE FROM COMING INTO CIRCUIT

IP.com Disclosure Number: IPCOM000008712D
Original Publication Date: 1998-Jun-01
Included in the Prior Art Database: 2002-Jul-04
Document File: 3 page(s) / 139K

Publishing Venue

Motorola

Related People

Toan Le: AUTHOR

Abstract

Cache memory usually partitions into subarrays which are selected into group to make double words (64 bits), quad words (128 bits) or more (in the future) so data out of each subarray usually wired-or the same bus with the other subarrays (before going to final stage as data driven out of cache) and this common bus is dynamic and very long. In the future microprocessor if the dynamic bus is too crowded and spacing between bus line has to be kept in minimum due to area restriction, the coupling noise can exist between bus lines. The coupling voltage exist at the middle line when precharge goes High and supposed the weak feedback P-device (Figure 1) to keep data at High but if the two adjacent lines are Low they will cause coupling voltage to drop off voltage of the middle significantly and if there is a large voltage drop off enough, it will cause a false data at the final stage. In future the process tend to increase coupling noise.

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Page 1 of 3

0 M

MOTOROLA Technical Developments

CIRCUIT OF PREVENTING COUPLING NOISE AND NOISE SPIKE FROM COMING INTO CIRCUIT

by Toan Le

1 OVERVIEW

  Cache memory usually partitions into subarrays which are selected into group to make double words (64 bits), quad words (128 bits) or more (in the future) so data out of each subarray usually wired-or the same bus with the other subarrays (before going to final stage as data driven out of cache) and this common bus is dynamic and very long. In the future microprocessor if the dynamic bus is too crowded and spacing between bus line

has to be kept in minimum due to area restriction, the coupling noise can exist between bus lines. The coupling voltage exist at the middle line when precharge goes High and supposed the weak feedback P-device (Figure 1) to keep data at High but if the two adjacent lines are Low they will cause coupling voltage to drop off voltage of the middle significantly and if there is a large voltage drop off enough, it will cause a false data at the final stage. In future the process tend to increase coupling noise.

Fig. 1

  The coupling noise is not only caused by between bus lines but also from the Reflections and Simultaneous Switching Noise.

  Reflections are caused by the discotinuities at the transmission lines and Simultaneous Switching Noise is caused by the inductances inherent in the power distribution lines since many circuits switch at the same time, the current supplied by the power lines can change rapidly and the inductive voltage drop along the line can cause the power supply

level to go down. The resulting voltage glitch is proportional to the switching speed, the number of drivers that switch simultaneously, and the effective inductance of the power lines (refer to "Circuits, Interconnections, and Pakaging for VLSI", H.B. Bakoglu).

  Therefore, any dynamic circuit having similar structure like in Figure 1 should be carefully considered if voltage glitch (noise spike) exists.

0 Mororda. Inc. 1998 73 June I998

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0 M MO-LA

Technical Developments

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