Method and apparatus for characterizing a circuit with multiple inputs
First Claim
1. A method of determining a characterization parameter of a circuit including at least one input, the method comprising the steps of:
- receiving an input signal presented to the at least one input of the circuit;
measuring a first delay associated with the circuit when the circuit is substantially unloaded;
measuring a second delay associated with the circuit when the circuit is loaded by a predetermined impedance;
determining a difference between the second delay and the first delay, the delay difference corresponding to a switching impedance associated with the circuit; and
determining the characterization parameter of the circuit based, at least in part, on the switching impedance associated with the circuit.
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Accused Products
Abstract
A method of characterizing a circuit comprises the steps of measuring a first delay associated with the circuit when the circuit is substantially unloaded; measuring a second delay associated with the circuit when the circuit is loaded by a predetermined impedance; determining a difference between the second delay and the first delay, the delay difference corresponding to a switching impedance associated with the circuit; and determining a characterization parameter of the circuit, the characterization parameter being a function of at least the switching impedance associated with the circuit. The methodologies of the present invention are directed primarily to individually evaluating pullup and pulldown delays with substantial precision (e.g., sub-picosecond) for a representative set of circuits in the presence of an arbitrary switching history.
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Citations
26 Claims
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1. A method of determining a characterization parameter of a circuit including at least one input, the method comprising the steps of:
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receiving an input signal presented to the at least one input of the circuit;
measuring a first delay associated with the circuit when the circuit is substantially unloaded;
measuring a second delay associated with the circuit when the circuit is loaded by a predetermined impedance;
determining a difference between the second delay and the first delay, the delay difference corresponding to a switching impedance associated with the circuit; and
determining the characterization parameter of the circuit based, at least in part, on the switching impedance associated with the circuit. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. A method of determining a thermal relaxation time of a circuit, comprising the steps of:
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measuring a first reference delay difference associated with the circuit at a first steady-state temperature, the delay difference corresponding to a difference between a first delay associated with the circuit when the circuit is substantially unloaded and a second delay associated with the circuit when the circuit is loaded by a predetermined impedance;
heating at least a portion of the circuit for a period of time to establish a thermal steady-state condition of the circuit at a second steady-state temperature, the second steady-state temperature being greater than the first steady-state temperature;
measuring a second reference delay difference associated with the circuit at the second steady-state temperature; and
determining an amount of time elapsed after heating has ceased for a measured delay difference associated with the circuit to substantially match the first reference delay difference, the amount of elapsed time corresponding to the thermal relaxation time of the circuit. - View Dependent Claims (12, 13, 14, 15, 16)
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17. Apparatus for determining a characterization parameter of a circuit including at least one input, the apparatus comprising:
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an interface operatively coupled to the at least one input of the circuit, the interface receiving an input signal presented to the circuit;
a first signal path operatively coupled to the interface, the first signal path being substantially unloaded and including a first circuit under test, the first circuit under test being substantially identical to the circuit to be characterized; and
at least a second signal path operatively coupled to the interface, the second signal path being loaded by a predetermined impedance and including a second circuit under test, the second circuit under test being substantially identical to the circuit to be characterized;
wherein the apparatus is configured to;
(i) measure a first delay associated with the first signal path;
(ii) measure a second delay associated with the second signal path;
(iii) determine a difference between the second delay and the first delay, the delay difference corresponding to a switching impedance associated with the circuit; and
(iv) determine the characterization parameter of the circuit based, at least in part, on the switching impedance associated with the circuit. - View Dependent Claims (18, 19, 20)
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21. Apparatus for determining a characterization parameter of a circuit including at least one input, the apparatus comprising:
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an interface operatively coupled to the at least one input of the circuit to be characterized, the interface receiving an input signal presented to the circuit;
switching circuitry operatively coupled to the circuit to be characterized, the switching circuitry be configured to selectively couple a predetermined impedance to an output of the circuit to be characterized in response to a control signal; and
at least one processor operatively coupled to the switching circuitry and generating the control signal, the at least one processor being operative to;
(i) measure a first delay associated with the circuit when the circuit is substantially unloaded;
(ii) measure a second delay associated with the circuit when the circuit is loaded by the predetermined impedance;
(iii) determine a difference between the second delay and the first delay, the delay difference corresponding to a switching impedance associated with the circuit; and
(iv) determine the characterization parameter of the circuit based, at least in part, on the switching impedance associated with the circuit. - View Dependent Claims (22, 23, 24)
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25. Apparatus for determining a thermal relaxation time of a circuit, the apparatus comprising:
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an interface operatively coupled to the circuit to be characterized, the interface receiving an input signal presented to the circuit;
a thermal generator, the thermal generator being in close relative proximity to at least a portion of the circuit to be characterized and being configurable for selectively controlling a temperature of the at least a portion of the circuit to be characterized in response to a control signal; and
at least one processor coupled to the thermal generator, the at least one processor generating the control signal and being operative to;
(i) measure a first reference delay difference associated with the circuit at a first steady-state temperature, the delay difference corresponding to a difference between a first delay associated with the circuit when the circuit is substantially unloaded and a second delay associated with the circuit when the circuit is loaded by a predetermined impedance;
(ii) heat at least a portion of the circuit for a period of time to establish a thermal steady-state condition of the circuit at a second steady-state temperature, the second steady-state temperature being greater than the first steady-state temperature;
(iii) measure a second reference delay difference associated with the circuit at the second steady-state temperature; and
(iv) determine an amount of time elapsed after heating has ceased for a measured delay difference associated with the circuit to substantially match the first reference delay difference, the amount of elapsed time corresponding to the thermal relaxation time of the circuit. - View Dependent Claims (26)
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Specification