Browse Prior Art Database

Tri State Current Switch Totem Pole

IP.com Disclosure Number: IPCOM000083711D
Original Publication Date: 1975-Jul-01
Included in the Prior Art Database: 2005-Mar-01
Document File: 2 page(s) / 30K

Publishing Venue

IBM

Related People

Barish, AE: AUTHOR [+2]

Abstract

Totem pole or push-pull drivers offer many advantages to designers requiring data transmission over busses with appreciable capacitive loading. high-speed, symmetrical performance is obtained at low-quiescent power. However, since the basic circuit always provides a low-impedance drive to one or the other of the logic states, it is not practical to "dot" drivers, and the testing of individual nets by forcing the outputs of the drivers to given states can cause high-power dissipation in the output.

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Tri State Current Switch Totem Pole

Totem pole or push-pull drivers offer many advantages to designers requiring data transmission over busses with appreciable capacitive loading. high-speed, symmetrical performance is obtained at low-quiescent power. However, since the basic circuit always provides a low-impedance drive to one or the other of the logic states, it is not practical to "dot" drivers, and the testing of individual nets by forcing the outputs of the drivers to given states can cause high-power dissipation in the output.

The drawing depicts a solution to these problems as applied to a driver implemented on a semiconductor chip. Under normal operating conditions T2 and T3 form a phase splitter, generating drive signals to the output transistors T5 and T6. The +DISABLE line is down and both T1 and T4 are in a high- impedance state. The operation of the basic driver is more fully disclosed in the IBM Technical Disclosure Bulletin publication entitled Current Switch "Totem Pole", by A. E. Barish and E. Colao, Vol. 16, No. 11, April 1974, page 3601.

In the testing mode the +DISABLE line is raised to an uplevel, causing T1 and T4 to turn on, which, in turn, pulls the bases of T5 and T6 to a level close to - VBB causing both transistors to be turned off. The output is now in a high- impedance 'DON'T CARE' state and may be forced to either an uplevel or a downlevel without excessive power dissipation.

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