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Speed Normalization of Logic Circuits

IP.com Disclosure Number: IPCOM000082974D
Original Publication Date: 1975-Mar-01
Included in the Prior Art Database: 2005-Feb-28
Document File: 2 page(s) / 48K

Publishing Venue

IBM

Related People

Parisi, JA: AUTHOR [+2]

Abstract

This arrangement solves a problem caused by variation in circuit time delay, resulting from processing variations in monolithic integrated chips or wafers. It is suggested that electrical signals be utilized to reduce such variations on chips where collector-to-substrate capacitance is a dominant parameter of circuit speed. Thus, the substrate voltage can be varied at specific locations upon the substrate to normalize operating speeds over the entire substrate.

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Speed Normalization of Logic Circuits

This arrangement solves a problem caused by variation in circuit time delay, resulting from processing variations in monolithic integrated chips or wafers. It is suggested that electrical signals be utilized to reduce such variations on chips where collector-to-substrate capacitance is a dominant parameter of circuit speed. Thus, the substrate voltage can be varied at specific locations upon the substrate to normalize operating speeds over the entire substrate.

In the figure, a single system power supply is used to bias the substrate of individual chips such that the circuit delay skew for all chips is minimized. A very negative power supply is utilized and the substrate voltage is generated from it. To generate the proper voltage at a particular location, the chip is first tested to determine its operating characteristics. Then a laser is utilized to personalize the resistor divider, whereby the chip becomes normalized and can be directly inserted into the desired system.

Personalization is accomplished by cutting on the dotted lines, as shown, to increase a resistor value and by shorting metal to diffusion between the X and Y terminals to decrease the value of the opposite resistor. Since the substrate voltage distribution is determined by the divider resistor, its value can be adjusted to any value between -V and ground. Consequently, a given chip can be permanently normalized by reducing or minimizing circuit skew on the...