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Improved Performance CMOS Off-Chip Driver

IP.com Disclosure Number: IPCOM000059966D
Original Publication Date: 1986-Feb-01
Included in the Prior Art Database: 2005-Mar-08
Document File: 2 page(s) / 59K

Publishing Venue

IBM

Related People

Wissel, L: AUTHOR

Abstract

A complementary metal-oxide semiconductor (CMOS) off-chip driver (OCD) circuit has been designed with improved turn-on and turn-off characteristics, resulting in reduced power dissipation. In the featured design illustrated, a P-channel device (T15) drives a series of resistors (R180-R188) to control di/dt during turn- on of pull-down devices (T180-T188) while T160-T168 drive the gates directly to turn off the pull-down devices quickly and reduce the overlapping conductance of the pull-up and pull-down. Although the conductance of T170-T176 during pull-down is not as much a concern, T14 could similarly be decomposed into a set of separate devices, like T160-T168, which would be connected to internal nodes of the resistor chain R170-R176 for quicker turn-off of T170-T176.

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Improved Performance CMOS Off-Chip Driver

A complementary metal-oxide semiconductor (CMOS) off-chip driver (OCD) circuit has been designed with improved turn-on and turn-off characteristics, resulting in reduced power dissipation. In the featured design illustrated, a P- channel device (T15) drives a series of resistors (R180-R188) to control di/dt during turn- on of pull-down devices (T180-T188) while T160-T168 drive the gates directly to turn off the pull-down devices quickly and reduce the overlapping conductance of the pull-up and pull-down. Although the conductance of T170-T176 during pull-down is not as much a concern, T14 could similarly be decomposed into a set of separate devices, like T160-T168, which would be connected to internal nodes of the resistor chain R170-R176 for quicker turn-off of T170-T176. Circuit simulations show a significant reduction in power consumption and output switching time. There is a small penalty in circuit layout area caused by the addition of a series of transistors used to drive the gates of T180-T188, but it is not significant for this type of circuit. Although this technique is described for an enabled tri-state OCD, it is equally applicable to a push-pull OCD.

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