Electronic digital logic circuitry – Interface – Supply voltage level shifting
Reexamination Certificate
2008-01-08
2008-01-08
Barnie, Rexford (Department: 2819)
Electronic digital logic circuitry
Interface
Supply voltage level shifting
C326S081000, C326S086000, C326S087000, C327S109000, C327S333000
Reexamination Certificate
active
11055228
ABSTRACT:
A pre-driver for large I/O pull-up and pull-down transistors is provided so that the I/O pull-up and pull-down transistors do not experience crowbar current, and the pre-driver circuit likewise does not experience crowbar current or require large driver transistors. One pre-driver circuit includes two NAND gates and two NOR gates with delay circuitry provided by two series inverters from a data input to a first node, and two additional series inverters from the first node to a second node. A further pre-driver circuit includes feedback from the pre-driver outputs to ensure its NMOS and PMOS transistors do not turn on together to create crowbar, while allowing faster switching. With the pre-driver circuit embodiments, a conventional level shifter can be used. Further with the pre-driver circuitry, slew rate control can be provided in the pull-up and pull-down driver circuitry, rather than in the pre-driver circuitry.
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Rhyne Fundamentals of Digital System Design, 1973, N.J., pp. 70-71.
Nguyen Andy T.
Zhou Shi-dong
Barnie Rexford
Crawford Jason
Tong Kin-Wah
Ward Thomas A.
Xilinx , Inc.
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