Xilinx, Inc.

Siuki Chan

Steven H C Hsieh

Robert O Conn

Christopher H Kingsley

Steven J Carey

Suresh Sivasubramaniam

William H Pabst

Dang Yun Yau

A system replicates the rapid temperature increases that are believed to cause microbump failures in certain applications of programmable logic devices (PLDs). The system configures a PLD under test with a circuit that switches a large amount of current and generates a large amount of heat when the circuit is clocked. The system monitors the temperature of the PLD and controls the switching of the circuit to achieve a predetermined temperature within a predetermined time period. The PLD is cooled, and the thermal cycling is repeated. The system detects microbump failures and communicates failure data to a computer for logging and analysis.

Self-heating mechanism for duplicating microbump failure conditions in FPGAs and for logging failures

Disclosed is a DC thermal energy generator for heating localized regions of an integrated circuit. The integrated circuit includes a pair of static circuits whose outputs are shorted, and are in contention. Contention causes current to flow through the circuits, generating heat. Integrated-circuit temperature can be varied by turning on more or fewer thermal energy generators. The thermal resistance of a packaged integrated circuit is computed using a well-known relationship among the integrated circuit's measured temperature, power consumption, and the ambient temperature.

Methods and circuits for measuring the thermal resistance of a packaged IC

In an embodiment of the present invention, an integrated circuit ('IC'), such as a field-programmable gate array ('FPGA') or a complex programmable logic device (&#x201c;CPLD&#x201d;), has a global clock buffer coupled to a first regional clock buffer through a first global clock spine. A first flip-flop is close to a first end of a first regional clock spine, and is coupled to a circuit block, such as a configurable logic block. The circuit block is coupled to the global clock buffer through a first routing portion and a second routing portion couples the first flip-flop to the circuit block so as to form a first clock ring allowing measurement of a first clock ring delay. In further embodiments, additional clock rings are configured in the IC, allowing measurements of additional clock ring delays. In suitably symmetric devices, skew along the regional clock spine is calculated from the clock ring delays.

Regional clock skew measurement technique

Described are methods and circuits for precisely measuring signal propagation delays between synchronous memory elements. The memory elements are configured as a down counter that produces a test signal with a test period that is some multiple of a clock common to the memory elements. When the signal path is sufficiently fast for data to transfer between the synchronous memory elements in a single clock cycle, the test period is one multiple of the clock period. However, when the signal path fails to pass either rising or falling edges between the synchronous memory elements in a single clock cycle, the test period is increased by one clock period, and when the signal path fails to pass both rising and falling edges in a single clock cycle, the test period is increased by two clock periods.

Circuits and methods for measuring signal propagation delays on integrated circuits

A configurable logic block ('CLB') in a programmable logic device ('PLD'), such as a complex programmable logic device (&#x201c;CPLD&#x201d;) or a field programmable gate array (&#x201c;FPGA&#x201d;), routes a timing signal, such as an external clock signal, through the CLB to provide a selected delay. The timing signal is routed through selected fast or slow pins of look-up tables (&#x201c;LUTs&#x201d;) in the CLB. CLBs are widely available in the PLD, allowing many timing signals to be delayed, and can be configured to account for board-specific or component-specific delays.

Programmable delay line using configurable logic block

Test methods and circuits isolate thermal effects from AC effects on circuit performance. Critical paths for a failing programmable logic device (PLD) are identified and tested. This testing minimizes the impact of power-supply flicker and noise by eliminating or inactivating circuitry not required to test the critical paths. DC thermal energy generators are instantiated on the PLD adjacent the critical paths to heat the critical paths to one or more test temperatures. The critical paths are then tested over an appropriate range of temperatures and supply-voltages.

Methods and apparatus for isolating critical paths on an IC device having a thermal energy generator

A glitchless T length pulse is generated by coupling a trigger signal and the latched output of a counter. The trigger signal initiates the start of the T length pulse, and the latched output of the counter initiates the end of the T length pulse after counting up a duration of T from a number of clock cycles of a clock signal. Latching the output of the counter prior to terminating the T length pulse eliminates glitches. Accuracy of the count determining the length of the T length pulse may be increased by latching the trigger signal with the clock signal to generated a synchronized trigger signal, and using the synchronized trigger signal to initiate the T length pulse.

Glitchless pulse generator

Described are methods for accurately measuring the skew of clock distribution networks on programmable logic devices. Clock distribution networks are modeled using a sequence of oscillators formed on the device using configurable logic. Each oscillator includes a portion of the network, and consequently oscillates at a frequency that depends on the signal propagation delay associated with the included portion of the network. The various oscillator configurations are defined mathematically as the sum of a series of delays, with the period of each oscillator representing the sum. The respective equations of the oscillators are combined to solve for the delay contribution of the included portion of the clock network. The delay associated with the included portion of the clock network can be combined with similar measurements for other portions of the clock network to more completely describe the network.

Methods and circuits for measuring clock skew on programmable logic devices

Disclosed is a DC thermal energy generator for heating localized regions of an integrated circuit. The integrated circuit includes a pair of static circuits whose outputs are shorted, and are in contention. Contention causes current to flow through the circuits, generating heat. Integrated-circuit temperatures can be varied by turning on more or fewer thermals energy generators. The thermal resistance of a, packaged integrated circuit is computed using a well-known relationship integrated circuit's measured temperature, power consumption, and the ambient temperature.

A method of estimating a capacitance of each resource in a programmable logic device (PLD) is described. The current drawn by a reference circuit implemented in the PLD is measured at a given frequency and operating voltage. The capacitance of the reference circuit is calculated using the current drawn, the frequency, and the operating voltage. The current drawn by a resource load coupled to the reference circuit is measured at the given frequency and operating voltage. The capacitance of the resource load coupled to the reference circuit is calculated using the current drawn, the frequency, and the operating voltage. The capacitance of the resource load may be calculated by subtracting the capacitance of the reference circuit from the capacitance of the resource load coupled to the reference circuit.

Determination of capacitances of individual resources in programmable logic devices

A method and structure for measuring the minimum lock frequency of a delay locked loop (DLL) within a programmable integrated circuit device such as a field programmable gate array (FPGA). The device is temporarily configured such that one DLL is programmed as a ring oscillator (RO) and connected directly to the input terminal of a second DLL (the DLL under test). Optionally, the RO is connected to the DLL under test through a divider to provide a lower DLL drive frequency. To test the DLL, the RO frequency is decreased until the DLL under test fails to lock. The frequency of the RO at that point is measured by comparing its output signal to the known frequency of an external clock source using two counters, and decremented until the DLL locks successfully. The lock frequency of the DLL under test is then computed from the ratio of the counter values.

Measuring a minimum lock frequency for a delay locked loop

A circuit measures a signal propagation delay through a series of memory cells on a programmable logic device. In one embodiment, a number of RAM cells are configured in series. Each RAM cell is initialized to store a logic zero. The first RAM cell is then clocked so that the output of the RAM cell rises to a logic one. The resulting rising edge from the output of the RAM cell then clocks the second RAM cell, which in turn clocks the next RAM cell in the series. The time required for a rising edge to traverse the entire sequence of latches is the cumulative time required for the output of each RAM cell to change in response to a clock edge. Consequently, the delay through the series of RAM cells provides a measure of the time required for one of the RAM cells to store data in response to a clock edge. In another embodiment, the RAM cells are arranged in a loop so that the sequence of RAM cells forms a ring oscillator, the period of which provides an indication of the time required for the RAM cells to store data in response to clock edges.

Circuit for measuring signal delays of synchronous memory elements

A test configuration for a programmable logic device (PLD) measures and stores the relative signal-propagation delays of a pair of signal paths extending into the PLD from PLD input pins. The PLD is configured to instantiate a ring oscillator that selectively includes either signal path in the ring. The oscillator exhibits a first oscillation period when the oscillator includes the first signal path, and exhibits a second oscillation period when the oscillator includes the second signal path. The difference between the first and second periods provides a measure of the difference between the signal propagation delays of the two paths of interest.

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Cupertino, CA, United States of America

Siuki Chan