Abstract: A delay circuit has a delay that is consistent under varying process and temperature conditions. The delay through a delay path is controlled by inserting resistors on the pull-up and pull-down paths of the delaying inverters. Each resistor has a resistance value that is determined by a varying a number of enabled similarly-sized transistors coupled in parallel across the resistor, rather than by varying the size of a single transistor. In one embodiment, a first transistor in each resistor is always enabled, while additional transistors are enabled using select signals. In one embodiment, the select signals are provided by configuration memory cells in a PLD. Other embodiments include additional delay paths and a multiplexer circuit that selects one of the delay paths. The described delay circuit is particularly useful in a DLL trim unit, where variations between resistors can cause jitter and locking problems in the DLL.

Abstract: An adaptable configuration interface for a programmable logic device (PLD). A PLD includes a plurality of configuration pins and circuitry implementing read and write protocols for reading data from and writing configuration data to the PLD. A register that is external to the PLD is connected to the configuration pins of the PLD, and a processor is coupled to the register. A first set of routines, each executable on the processor, are configured to read and write values from and to the register. A second set of routines, each executable on the processor, provide an application programming interface for the configuration and readback of data from the PLD via the first set of routines. The layered structure of the interface routines aids in incrementally changing from a software controlled configuration interface to an interface that is a combination of hardware and software.

Abstract: A data processing system having a user configurable memory controller, one or more local block RAMs, one or more global block RAMs and a processor core can be configured in a single field programmable gate array (FPGA). The address depth of the global block RAMs and the number of wait states can be selected by a user, and they can be set either prior to configuration of the FPGA or programmed using instructions of the processor core. The number of wait states of the local block RAM is also user selectable. An algorithm that can optimize the address depth and the number of wait states to achieve a performance level is also disclosed. The present invention can be applied to designs having separate instruction and data sides.

Abstract: A method for determining contact resistance between an automated test equipment (ATE) system and a device under test (DUT). The DUT is configured to drive a known voltage to a pin. The ATE system is then controlled to force a first test current into the DUT at that pin. A board precision measurement unit (BPMU) of the ATE system then measures the voltage VM+ required to force the first test current. The ATE system is then controlled to force a second test current to flow out of the DUT at the same pin. The ATE system controls the second test current to have the same magnitude (but opposite direction) as the first test current. The BPMU then measures the voltage VM− required to force the second test current. The contact resistance is then determined in response to the measured voltages VM+ and VM−, and the magnitude of the test current.

Abstract: A BGA-type capacitor structure including a conventional chip capacitor mounted on the upper surface of an inexpensive substrate, and having solder balls mounted on a lower surface of the substrate. Lands that are required to mount the chip capacitor are formed on the substrate, which is offset from the surface of a PCB by the solder balls. The substrate can be a thin sheet of polyimide tape that is etched or perforated to provide holes through which the solder balls contact the lands used to mount the chip capacitor. An assembly incorporating the BGA capacitor structure includes a PCB having an array of metal vias extending between opposing upper and lower surfaces, a BGA IC mounted on the upper surface and soldered to first ends of the metal vias. The capacitor structures are soldered to contact pads formed on the lower surface of the PCB.

Abstract: A driver circuit drives heavily loaded signals at high speeds with a reduced crowbar current. One-shots are used to drive the output pullup and pulldown, thereby minimizing the period when both devices are turned on. One embodiment includes an inverter, a one-shot low, a one-shot high, a pullup, and a pulldown. An input signal drives the inverter and the two one-shots. The inverter output terminal is coupled to the driver output terminal, as are the pullup and pulldown. The one-shot low circuit controls the pullup. The one-shot high circuit controls the pulldown. Another embodiment includes two pre-driver circuits, one controlling an output pullup and the other controlling an output pulldown. Each of the pre-driver circuits is implemented using a one-shot low and a one-shot high, as described above. One such embodiment is an output driver for a PLD, and the one-shots include various programmable options.

Abstract: Described are a method of programming a programmable logic device using encrypted configuration data and a programmable logic device (PLD) adapted to use such encrypted data. A PLD is adapted to include a decryptor having access to a non-volatile memory element programmed with a secret decryption key. Some or all of the decryptor can be instantiated in configurable logic on the FPGA. Encrypted configuration data representing some desired circuit functionality is presented to the decryptor. The decryptor then decrypts the configuration data, using the secret decryption key, and configures the FPGA with the decrypted configuration data. Some embodiments include authentication circuitry that performs a hash function on the configuration data used to instantiate the decryptor on the PLD. The result of the hash function is compared to a proprietary hash key programmed into the PLD. Only those configuration data that produce the desired hash result will instantiate decryptors that have access to the decryption key.

Abstract: A programmable capacitor in an integrated circuit (IC) comprises a conductive line located parallel to an interconnect. When a bias voltage is applied to the conductive line, a parasitic capacitance is created between the interconnect and the conductive line. By properly sizing and locating the conductive line, a desired capacitance can be coupled to the interconnect. A bias control circuit can apply or remove the bias voltage from the conductive line, thereby enabling the capacitance to be coupled or decoupled, respectively, from the interconnect. Because of its simple construction, multiple capacitive structures can be formed around a single interconnect to provide capacitive adjustment capability. By changing the number of conductive lines to which the bias voltage is applied, the total capacitance provided by the multiple capacitive structures can be varied. A feedback loop can be incorporated to provide adjustment during IC operation.

Abstract: An integrated circuit includes analog test cells to determine if an analog signal is within a predetermined voltage or current range. The test cell uses one or more analog reference signals to establish boundaries of a test range. Different embodiments of the analog test cells selectively test multiple analog signals provided in an integrated circuit. A test system can be provided to test multiple analog signals of an integrated circuit by scanning multiple analog test cells distributed throughout the integrated circuit and providing the test data for analysis. An analog circuit of an integrated circuit can be tested at different stages in manufacturing, including during a wafer stage prior to separation of individual circuit dice. Further, analog circuitry can be tested and characterized without the need for analog or digital/analog testers. In contrast, a digital only tester can be used to test analog circuitry.

Abstract: A trigger circuit for an In-System Programmable (ISP) memory device that operates with a JTAG interface. The trigger circuit receives instruction signals from the JTAG control circuitry, and limits the duration of these instruction signals to avoid erroneously repeating ISP programming operations. The trigger circuit includes a first logic circuit, a delay circuit, and a second logic circuit. The first logic circuit generates a logic high output when both the JTAG RUN-TEST and a program instruction signal are simultaneously asserted, and causes the second logic circuit to toggle the limited duration instruction signal into a logic high state. The delay circuit also detects the simultaneous assertion of the JTAG RUN-TEST and a program instruction signal, and generates a cancellation signal after a predetermined number of clock cycles. The cancellation signal causes the second logic circuit to toggle the limited duration instruction signal into a logic low state.

Abstract: Fault coverage for the programmable interconnect of a programmable logic device (PLD) is provided. A user's design is modeled, thereby determining the programmable interconnect path in the device. The user's logic design is then modified, thereby facilitating the detection of faults. Specifically, any function generators in the PLD are implemented as predetermined logic gates, thereby forming a logic gate tree design. The synchronous elements in the user's design are preserved and transformed, if necessary, to provide controllability. Then, a vector can be exercised in the new design. A first readback of the PLD can be compared to a second readback of a fault-free model of the design.

Abstract: Many electronic devices, such as computers and printers, communicate data to each other over wireline or wireless communications links. One component vital to such communications is a voltage-controlled oscillator (VCO)—a circuit that outputs an oscillating signal having an oscillation frequency based on a control voltage. Conventional VCOs adjust frequency based on a single control voltage input, which makes them vulnerable to unintended changes in the control voltage (and power-supply voltages relative to the control voltage.) These voltage changes cause frequency deviations that can make communications between devices less reliable. Accordingly, the present inventors devised a VCO that includes differential frequency control—frequency control based on the difference of two control voltages.

Abstract: A high speed data communication system includes a receiver to recover data and clock signals from communicated data. The receiver circuit has a dual phase lock loop (PLL) circuit. A fine loop of the PLL includes a phase detector providing a differential analog voltage output. Transconductance circuitry converts the differential analog voltage output to a low current analog output. The transconductance circuitry has a high impedance output, a small transconductance value and can provide variable gain control. A coarse loop of the PLL allows for frequency acquisition of an internal oscillator.

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 differential amplifier amplifies input signals and includes first and second differential input transistor pairs. The first input pair controls output voltages by adjusting sink currents coupled to the outputs. The second pair of transistors compliments the first pair by dynamically adjusting a current sourced to the outputs. A common mode circuit has also been described that adjusts both the current sourced to the outputs and the sink currents. In one embodiment, the amplifier is fully differential and controls both current source transistors and current sink transistors coupled to the amplifiers outputs.

Abstract: A track-and-hold circuit including a pair of circuits each receiving input signals and providing half of a differential output signal. Each of the circuits of the pair includes an amplifier, and a configurable switch circuit coupled to a selectable reference voltages based on an expected input signal type. Each circuit includes a first switched capacitor circuit to sample its respective first input signal in response to a first clock phase, and to couple the sampled first input signal between the output and the negative input of the amplifier in response to a second clock phase. A second switched capacitor circuit samples its respective second input signal relative to an external common mode voltage in response to the first clock phase, and couples the sampled second input signal to a positive amplifier input relative to the selected reference voltage in response to the second clock phase.

Abstract: A structure and method to prevent barrier failure is provided. The present invention replaces a standard titanium-nitride (TiN) barrier metal layer with two separately-formed TiN layers. The two TiN layers provide smaller, mismatched grain boundaries. During subsequent tungsten deposition using WF6, the WF6 finds it difficult to penetrate through the mismatched grain boundaries, thereby minimizing any possibility of “tungsten volcano”. One embodiment includes a native or a grown oxide formed between the two TiN layers, thereby providing yet another diffusion barrier to the WF6 and acting as a glue layer between the two TiN layers. The present invention provides a thin and strong barrier metal layer with minimal barrier failures.

Abstract: A method and apparatus for developing placement characteristics of a circuit design in conjunction with developing functional aspects of the circuit. In various embodiments, an application programming interface (API) is programmed in a hardware definition language (HDL). The API provides placement directives that can be called from the HDL code that defines functional characteristics of the circuit. The API can also be used in a testbench in order to analyze both the functional and physical placement characteristics of the design. Since the API is programmed in HDL, the placement generated during the implementation phase is the same as the placement analyzed during functional simulation.

Abstract: A configurable logic element (CLE) for a field programmable gate array (FPGA) includes “expanders”, i.e., connectors that allow fast signal communication between logic blocks. Expanders allow the configurable interconnection of a plurality of logic blocks, or portions thereof, to form a single logical entity that can implement large user circuits such as PALs, lookup tables, multiplexers, tristate buffers, and memories. One embodiment includes a configurable logic block. In a first mode, the logic block provides two N-input LUTs having N shared inputs and two separate outputs. The outputs are then combined using an expander to generate an (N+1)-input function. In a second mode, the logic block provides two N-input LUTs having M unshared inputs. An optional third mode provides a plurality of product term output signals based on the values of the N input signals.

Abstract: A method for dynamically burn-in testing a PLD by either configuring or fabricating the PLD to implement a self-executing logic operation that automatically and repeatedly turns on and off selected transistors of the PLD using only static test signals. The self-executing logic operation implemented by the PLD includes a driving logic function (e.g., an oscillator) and a driven logic function (e.g., a counter). The PLD is placed on a conventional load board and heated in a conventional oven while static test signals are applied to selected terminals of the PLD through the load board, thereby causing the PLD to implement the self-executing logic operation.