Cypress Semiconductor Corporation

Oracle America, Inc.

Hang Kwan

Suresh M Menon

Randy T Ong

Richard W Smith

Manzurul Khan

A pruning algorithm for generating a reverse donut model (RDM) for running timing analysis for a block in an IC includes logic to reduce a hierarchical model of the IC to a single level flat model. A block from a plurality of blocks that make up the IC is identified from the single level flat model of the IC. The pruning algorithm is further used to initialize a timer and to define timing constraints associated with each of a plurality of input and output pins associated with the identified block. A RDM for the identified block is generated by identifying and including connectivity information associated with a plurality of input and output pins in an outer boundary of the identified block and at least one layer of interface connection between each of the plurality of input and output pins in the outer layer of the identified block and one or more circuit elements external to the identified block in the IC interfacing with each of the plurality of input and output pins in the identified block. The generated RDM acts as a blackbox for the identified block and is used in place of the identified block for running the timing analysis.

Reverse donut model

The present invention minimizes the noise voltage associated with the switching of output driver transistors of integrated cicruits caused by the rapid change in value of the current, expressed by the term di/dt, from the load into the driver transistors through the package leads. The present invention uses a programmable coarse current control (CCC) circuit and a programmable fine current control (FCC) circuit that control the pull-down output transistors. The FCC creates two time periods, after which it prevents the CCC from controlling an output pull-down transistor. The FCC and the CCC are used to reduce the di/dt dependent voltage noise by controlling the slope and the shape of the output voltage pull-down characteristics.

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San Bruno, CA, United States of America

Hang Kwan