Abstract: A voltage regulator circuit in an integrated circuit (IC) device such as a Complex Programmable Logic Device (CPLD) comprises a reference voltage generator, a tuning circuit, and an output driver circuit. The reference voltage generator converts an external supply voltage provided to the IC device into a stable reference voltage. The tuning circuit converts the stable reference voltage into a desired internal supply voltage, such as the reduced voltage required by deep sub-micron transistors. The output driver circuit provides the desired internal supply voltage with sufficient current to properly power the circuits of the IC device. The tuning circuit includes an op-amp and resistive elements configured in a voltage divider configuration in the negative feedback loop of the op-amp. The output of the op-amp can be set to the desired internal supply voltage by properly sizing the resistive elements.

Abstract: A method and apparatus for placement into a programmable gate array of input-output (I/O) design objects having different voltage standards. The programmable gate array has a plurality of sites arranged into banks supporting interfaces with a plurality of different input and output voltage standards. In an example embodiment, I/O design objects are placed into IOBs of the programmable gate array by first performing simulated annealing that considers conflicts between design object voltage standards as placed into the IOBs. Then, a bipartite matching is performed using placement results from simulated annealing. Finally, if the bipartite matching does not produce a feasible placement, standards are assigned to the banks based on the previous placement results, and the bipartite matching process is repeated.

Abstract: A delay lock loop uses a clock phase shifter with a delay line to synchronize a reference clock signal with a skewed clock signal. The delay line is coupled to a reference input terminal of the delay lock loop and generates a delayed clock signal that is provided to the clock phase shifter. The clock phase shifter generates one or more phase-shifted clock signals from the delayed clock signal. An output generator coupled to the delay line, the clock phase shifter, and an output terminal of the delay lock loop provides either the delayed clock signal or one of the phase-shifted clock signals as an output clock signal of the delayed lock loop. The propagation delay of the delay line is set to synchronize the reference clock signal with the skewed clock signal, which is received on a feedback input terminal of the delay lock loop. A phase detector compares the reference clock signal and the skewed clock signal to determine the appropriate propagation delay for the delay line.

Abstract: A configurable logic block (CLB) having a plurality of identical configurable logic element CLE) slices is provided. Each CLE slice includes a plurality of function generators (lookup tables) that can be configured to form a random access memory (RAM). The width and depth of the RAM are selectable by controlling the routing of signals within the CLE slices. A hierarchy of wide function multiplexers (F5, F6, and F7 multiplexers) are provided to selectively route read data values from the lookup tables. Another set of multiplexers is used to selectively route write data values to the lookup tables. These multiplexers can be configured to provide a single write data value to all of the lookup tables to form a deep RAM. Alternatively, these multiplexers can be configured to provide one write data value to half of the lookup tables, and another write data value to the other half of the lookup tables.

Abstract: Programmable logic devices which include multiple blocks of combinatorial function generators and storage elements, and which are interconnected by a programmable interconnect structure are used, among other things for performing arithmetic functions which use logic for generating the carry function. When a large number of bits is to be processed, the carry function typically causes significant delay or requires significant additional components to achieve a result at high speed. The present invention provides dedicated hardware within the logic blocks for performing the carry function quickly and with a minimum number of components. The invention takes advantage of the fact that a carry signal to be added to two bits can be propagated to the next more significant bit when the two binary bits to be added are unequal, and that one of the bits can serve as the carry signal when the bits are equal.

Abstract: A duty cycle correction circuit and method that accept an unsymmetrical input clock signal and provide therefrom an output clock signal having a 50% duty cycle. One circuit according to the invention includes an input clock terminal supplying a input clock signal, and a delay line driven by the input clock signal and supplying a plurality of intermediate clock signals delayed from the input clock signal by incremental unit delays. A clock multiplexer selects from among these intermediate clock signals, under control of a multiplexer control circuit, the clock signal that is most nearly 180 degrees offset from the input clock signal. The selected clock signal is then combined with the input clock signal in an output clock generator to generate an output clock signal having a 50% duty cycle. In one embodiment, the duty cycle correction circuit includes a delay stage comprising a delay element that can selectively add a half-unit delay to the input clock signal.

Abstract: A plurality of flash electrically erasable programmable read only memory (EEPROM) cells is disclosed wherein metal lines couple both the sources and the drains of the flash cells. Reading of these flash cells is accomplished by applying a positive voltage to the source and reading from the associated metal source line. A soft erase scheme for increasing the threshold voltage of over-programmed flash cells is provided that prevents the leakage caused by applying a positive voltage to the drain.

Abstract: A RAM block includes a circuit for causing the RAM to provide a reset value on the output or a previously captured output value from the RAM when a Reset signal is active. The Reset signal does not change the RAM contents but causes all outputs of the block RAM to be either a reset value or a capture value, as selected by the user. This is useful when the RAM block is configured as a state machine. Thus, in an FPGA or other programmable device, an application can start the state machine in a known state with all address bits equal to 0 and can reset the state machine to this startup state. When the reset signal is active, the state machine can feed back the reset value or capture value to the address inputs of the RAM block that receive state feedback data, regardless of the data actually in those locations.

Abstract: During the development of process parameters for fabricating an integrated circuit, a test circuit is provided on the wafer that provides rapid identification of process problems (i.e., before failure analysis), detects defects down to a part-per-million (PPM) level, and identifies the precise location of any defects, thereby facilitating rapid failure analysis during the development and refinement of IC fabrication processes used to fabricate an integrated circuit (IC). In a first embodiment, the test circuit includes parallel conductive paths that are selectively connected to a signal source by pass transistors. Open circuits are identified by sequentially connecting one end of the conductive paths to the signal source and measuring the current at the other end. In a second embodiment, the test circuit includes perpendicular sets of overlapping conductors. Short conductive segments extend in parallel with a first set of conductors that are electrically connected to a second set of conductors.

Abstract: A negative voltage detector is disclosed wherein a resistor divider circuit is used to translate a negative voltage into a standard CMOS logic low or logic high value. The small area consumed by the negative voltage divider of the present invention allows multiple device placement within a logic device without the consumption of much area on the logic device. Additionally, the multiple devices placed may detect different negative voltage thresholds with a simple tuning of device components.

Abstract: A PLD includes buffered interconnect resources and configurable logic circuits that are controlled by data stored in a configuration memory. Each buffer of the buffered interconnect resources includes a feedback pull-up transistor. To avoid crowbar current problems, a high voltage is transmitted to the input terminals of all buffers before configuration, thereby biasing all buffers into a high feedback voltage mode. In one embodiment, the high voltage is transmitted to the buffers using a global control signal that forces all output drivers to generate high output voltages, and then turning on all pass transistors of the interconnect resources to broadcast the high voltages to every buffer. After configuration, the global control signal is de-activated. In another embodiment, each buffer circuit includes a second pull-up device that is turned on at power-up to force all buffers into the high feedback mode.

Abstract: Described are systems and methods that take advantage of the run-time reconfigurability of modern programmable logic devices to efficiently implement content-addressable memory (CAM) circuits. Rather than using configurable logic to compare CAM entries stored in flip-flops, a CAM in accordance with the invention uses configurable logic for both data storage and comparison. A CAM in accordance with one embodiment of the invention includes a number of programmable look-up tables on a programmable logic device collectively configured to produce a “match” signal in response to data provided on a series of data input terminals. Configuration data determines the particular pattern to which the CAM responds, so new CAM entries are introduced by configuring (or reconfiguring) one or more of the look-up tables.

Abstract: The maximum propagation speed of an electrical signal travelling on a conductor in an integrated circuit is limited by the dielectric constant of the dielectric material surrounding the conductor. Rather than transmitting an electrical signal through a conductor that is surrounded with a dielectric material having a dielectric constant of two or more, the signal is propagated as an electromagnetic wave through air at a much higher speed across the surface of the integrated circuit. In one embodiment, a radio frequency (RF) signal is passed into an integrated circuit package via a transmission line. The transmission line supplies the RF signal to a waveguide-like structure disposed above the integrated circuit inside the package. The RF signal propagates as an electromagnetic wave through air in the waveguide structure across the upper surface of the integrated circuit.

Abstract: The maximum propagation speed of an electrical signal travelling on a conductor in an integrated circuit is limited by the dielectric constant of the dielectric material surrounding the conductor. Rather than transmitting an electrical signal through a conductor that is surrounded with a dielectric material having a dielectric constant of two or more, the signal is propagated as an electromagnetic wave through air at a much higher speed across the surface of the integrated circuit. In one embodiment, a radio frequency (RF) signal is passed into an integrated circuit package via a transmission line. The transmission line supplies the RF signal to a waveguide-like structure disposed above the integrated circuit inside the package. The RF signal propagates as an electromagnetic wave through air in the waveguide structure across the upper surface of the integrated circuit.

Abstract: A shift register system is disclosed wherein shift registers buffering memory data perform shift operations in response to a set of sub-clock signals. The set of sub-clock signals comprise nested sub-clock signals having non-overlapping transitions formed from a system clock signal or power on reset signal. Each shift register (or bank of shift registers) responds to a different sub-clock signal. As a result, shift operations are spread out over a period of time rather than occurring simultaneously. Thus, the current drawn during each shift operation is similarly spread out over a period of time. The maximum current drawn during any one shift operation is inversely proportional to the number of non-overlapping sub-clock signal. Therefore, the maximum current drawn (i.e., current spike) drawn during memory operations is minimized.

Abstract: An ESD protection circuit includes a bipolar transistor, a resistor, and a zener diode formed on and within a semiconductor substrate. The resistor extends between the base and emitter regions of the transistor so that voltage developed across the resistor can turn on the transistor. The zener diode is formed in series with the resistor and extends between the base and collector regions of the transistor. Thus configured, breakdown current through the zener diode, typically in response to an ESD event, turns on the transistor to provide a nondestructive discharge path for the ESD. The zener diode includes anode and cathode diffusions. The cathode diffusion extends down into the semiconductor substrate in a direction perpendicular to the substrate. The anode diffusion extends down through the cathode diffusion into the semiconductor substrate. The anode diffusion extends down further than the cathode diffusion so that the zener diode is arranged vertically with respect to the substrate.

Abstract: A matched filter arrangement and an FPGA-implemented tap arrangement for a matched filter are described in various embodiments. In an n-tap filter to match a code sequence, each of taps 1 through (n-1) includes a configurable adder-subtractor. A code storage element is coupled to the adder-subtractor to select either addition or subtraction in accordance with a corresponding bit of the code sequence. The output of the adder-subtractor is coupled to a partial-result storage element, which is part of a chain of partial-result storage elements. The last partial-result storage element in the chain is coupled to the data input of an adder-subtractor in another tap. The last tap includes an adder-subtractor and a single storage element for storage of the final result.

Abstract: A two-transistor flash EPROM cell for high-speed high-density PLD applications is provided. The two-transistor cell includes a storage transistor connected in series to an access transistor. The storage transistor prevents problems associated with both over-erase and punch-through, and allows for scaling of the gate length to realize 5V cell programming.

Abstract: A three terminal non-volatile memory element includes a standard (low voltage) CMOS transistor, i.e. a storage transistor, having a drain coupled to a read bit line and a source connected to ground. The storage transistor is programmed by applying a high programming voltage to its gate, thereby rupturing the gate oxide of the storage transistor. Of importance, in submicron technology, the source and drain regions of the storage transistor merge, thereby providing a highly reliable, conductive path. Thus, the state of the memory cell can be advantageously read solely via the read bit line.

Abstract: A programmable logic device (PLD) comprises at least one configurable element, and a plurality of programmable logic elements for configuring the configurable element(s). Alternatively, a PLD comprises an interconnect structure and a plurality of programmable logic elements for configuring the interconnect structure. In either embodiment, at least one of the programmable logic elements includes N memory cells. A predetermined one of the N memory cells forms part of a memory slice, wherein at least a portion of each slice of the programmable logic device is allocated to either configuration data or user data memory. Typically, one memory slice provides one configuration of the programmable logic device. In accordance with one embodiment, a memory access port is coupled between at least one of the N memory cells and either one configurable element or the interconnect, thereby facilitating loading of new configuration data into other memory slices during the one configuration.