Xilinx, Inc.

Cypress Semiconductor Corporation

Randy T Ong

Khue Duong

Samuel Broydo

Sheau-suey Li

Suresh M Menon

Edel M Young

Hang Kwan

For an FPGA having a configuration memory arranged in rows and columns, a programmable address decoder with a counter selects the order in which columns of memory cells will be programmed and selects which columns of memory cells are programmed. The decoder structure addresses a particular column only when an address provided by the counter matches an address in the memory cells of the decoder for that column. Bitstreams intended for older devices can be successfully loaded into newer devices. Bitstreams developed for future devices with additional features can be loaded into devices with fewer features, and the additional features are not used. The counter can be set to count not in sequential order so that if extra columns are provided, a defective column of the FPGA controlled by a corresponding column of configuration memory cells can be bypassed.

Programmable address decoder for programmable logic device

An ESD protection circuit combines a split bipolar transistor with a transistor layout which exhibits very high tolerance to ESD events. The split bipolar transistor divides current among many segments and prevents the current hogging which often causes an ESD failure. Several splitting structures are disclosed, each combining a resistor in series with each segment to distribute current evenly. The transistor takes advantage of the snap-back effect to increase current carrying capacity. Layout positions metal contacts away from regions of highest energy dissipation. Layout also allows high currents to be dissipated through ESD protection structures and not through circuit devices such as output drivers or through parasitic bipolar transistors not designed for high current. Sharp changes in electron density are avoided by the use of high-diffusing phosphorus in N-regions implanted to both lightly and heavily doped levels. Critical corners are rounded rather than sharp. Certain P-type channel stop implants are positioned away from nearby N-regions to increase breakdown voltage.

ESD protection circuit

A programmable logic device includes a configuration memory expanded to store two or more complete sets of configuration data. A switch on the output of the configuration memory controls the selection of the configuration data applied to the configurable logic block. Each configurable logic block has one data storage device per set of configuration data. The configurable logic blocks may be re-configured within a user's clock cycle. During a first period, the switch on the output of the configuration memory selects and passes configuration data from the first set of configuration data. The configurable routing matrix and configurable logic block are configured according to this first set of configuration data and store results in a first storage device. During a second period, the switch selects and passes the second set of configuration data. Then the configurable routing matrix and configurable logic block are configured according to the second set of configuration data, the function generator performs the second logic function, and the outputs are passed or stored by the second output device. At the end of the last period the function is available to the user.

Programmable logic device which stores more than one configuration and

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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Cupertino, CA, United States of America

Randy T Ong