Self-test solution for delay locked loops
First Claim
1. A built-in self-test system for use in circuitry having two or more delay locked loops (DLLs), comprising:
- a first DLL having a first delay input, a first clock input disposed to receive a clock input signal and a first clock output providing a first clock output signal delayed in comparison with the clock input signal;
a second DLL having a second delay input, a second clock input disposed to receive the clock input signal and a second clock output providing a second clock output signal delayed in comparison with the clock input signal;
a test controller provides a first delay amount over the first delay input of the first DLL to create a start offset between the first clock output signal and the second clock output signal and further provides at least one common delay amount to both the first delay input of the first DLL and the second delay input of the second DLL;
a sample component that creates a test dataset by sampling the second clock output signal from the second DLL during at least one edge of the first clock output signal from the first DLL; and
a compare component that performs a comparison of the test dataset with a comparison dataset and produces a comparison result from a comparison of the first clock output signal from the first DLL with the second clock output signal from the second DLL.
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Accused Products
Abstract
A built-in self test (BIST) circuit and method is provided to test a first and a second DLL. The first DLL has a first delay input, a first clock input disposed to receive a clock input signal, and a first clock output that provides a first clock output signal delayed in comparison with the clock input signal. The second DLL has a second delay input, a second clock input disposed to receive the clock input signal, and a second clock output signal delayed in comparison with the clock input signal. The BIST circuitry provides a first delay amount over the first delay input creating a start offset between the first and second clock output signals. If the first DLL is functioning properly the start offset between the output signals should remain unchanged even after the BIST circuitry provides an additional common delay amount to the first and second delay inputs.
353 Citations
22 Claims
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1. A built-in self-test system for use in circuitry having two or more delay locked loops (DLLs), comprising:
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a first DLL having a first delay input, a first clock input disposed to receive a clock input signal and a first clock output providing a first clock output signal delayed in comparison with the clock input signal; a second DLL having a second delay input, a second clock input disposed to receive the clock input signal and a second clock output providing a second clock output signal delayed in comparison with the clock input signal; a test controller provides a first delay amount over the first delay input of the first DLL to create a start offset between the first clock output signal and the second clock output signal and further provides at least one common delay amount to both the first delay input of the first DLL and the second delay input of the second DLL; a sample component that creates a test dataset by sampling the second clock output signal from the second DLL during at least one edge of the first clock output signal from the first DLL; and a compare component that performs a comparison of the test dataset with a comparison dataset and produces a comparison result from a comparison of the first clock output signal from the first DLL with the second clock output signal from the second DLL. - View Dependent Claims (2, 3, 4, 5, 6)
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7. A built-in self-test method for two or more delay locked loop (DLLs) comprising the steps of:
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providing a clock input signal to a first DLL and the clock input signal to a second DLL, wherein the clock input signal delayed by the first DLL corresponds to a first clock output signal and the clock input signal delayed by the second DLL corresponds to a second clock output signal; initializing the first DLL with a first delay amount causing the first clock output signal from the first DLL to become offset from the second clock output signal of the second DLL by a start offset; modifying both the first delay amount provided to the first DLL and a second delay amount provided to the second DLL by a common delay amount selected from a set of common delay amounts; determining if modifying both the first delay amount to the first DLL and the second delay amount to the second DLL by the common delay amount causes a change in the offset between the second clock output signal and the first clock output signal set to the start offset in the initializing step; and indicating the first DLL may not be functioning properly when the determining step indicates that the start offset set initially between the first clock output signal and the second clock output signal has changed in response to modifying both the first delay amount and the second delay amount by the common delay amount. - View Dependent Claims (8, 9, 10, 11, 12, 13, 14)
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15. A computer program product for operating a built-in self-test for two or more delay locked loop (DLLs), tangibly stored on a computer readable medium, comprising instructions operable to cause a programmable processor to:
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provide a clock input signal to a first DLL and to a second DLL, wherein the clock input signal delayed by the first DLL corresponds to a first clock output signal and the clock input signal delayed by the second DLL corresponds to a second clock output signal; initialize the first DLL by a first delay amount that causes the first clock output signal of the first DLL to be offset from the second clock output signal of the second DLL by a start offset; modify both the first delay amount provided to the first DLL and a second delay amount provided to the second DLL by a common delay amount selected from a set of common delay amounts; determine if modifying both the first delay amount to the first DLL and the second delay amount to the second DLL by the common delay amount causes a change in the offset between the second clock output signal and the first clock output signal set initially to the start offset; and indicate that the first DLL may not be functioning properly when the offset between the second clock output signal and the first clock output has changed from the start offset in response to a modification of both the first delay amount and the second delay amount by the common delay amount. - View Dependent Claims (16, 17, 18, 19, 20, 21, 22)
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Specification