Browse Prior Art Database

On-Chip Tristate Driver

IP.com Disclosure Number: IPCOM000050320D
Original Publication Date: 1982-Oct-01
Included in the Prior Art Database: 2005-Feb-10
Document File: 2 page(s) / 56K

Publishing Venue

IBM

Related People

Schettler, H: AUTHOR [+2]

Abstract

Semiconductor chip bus lines, which account for a considerable capacitive load, are driven by the described tristate driver without incurring switching speed reductions.

This text was extracted from a PDF file.
At least one non-text object (such as an image or picture) has been suppressed.
This is the abbreviated version, containing approximately 69% of the total text.

Page 1 of 2

On-Chip Tristate Driver

Semiconductor chip bus lines, which account for a considerable capacitive load, are driven by the described tristate driver without incurring switching speed reductions.

Fig. 1 shows a first example of the tristate driver which essentially consists of two NAND gates 1 and 2, whose data inputs D1 and D2 are interconnected. Control signal HZ, switching the driver to its high impedance state, is applied to the third input C of NAND gate 2. The cathode of Schottky diode SD1, whose anode is linked with supply voltage V(CC) applied to the chip by resistor R1, is also connected to input C. The connecting point of Schottky diode SD1 and resistor R1 is linked with output 01 of NAND gate 1 and the base of an additional transistor T8 which, similar to the NAND gate transistors, is provided with an antisaturation diode. The collector of transistor T8 is connected to supply voltage V(P) which is generated from the higher chip supply voltage V(CC) and simultaneously serves as the supply voltage for NAND gates 1 and 2. The emitter of transistor T8 is connected to output 02 of NAND gate 2 which is also the output of the tristate driver. Transistor T8 is series-connected to output transistor T7, forming the collector resistor of this transistor.

Application of a high potential to control input C of NAND gate 2 prevents the high impedance state in which driver output transistors T7 and T8 are non- conductive. In this case, the state of the driver is determi...