Circuit for testing the AC timing of an external input/output terminal of a semiconductor integrated circuit
View Patent ↗In a semiconductor integrated circuit, one of two signals generated from a first logic circuit is delayed in a first delay addition circuit, looped back by an input/output terminal, and then inputted to a second logic circuit. The other output of the first logic circuit is looped back by a reference input/output terminal, further delayed in a second delay addition circuit, and then inputted to the second logic circuit. By varying respective amounts of delay added by the first and second delay addition circuits from each other, AC timing specifications are satisfied and it is determined whether or not the semiconductor integrated circuit has passed a test based on whether or not the output of the second logic circuits is a desired signal relative to the input of the first logic circuit.
1. A semiconductor integrated circuit comprising:
a first logic circuit for outputting an output signal in accordance with an operation pattern input signal;
a first delay addition circuit for delaying the output of the first logic circuit by an amount of delay in accordance with a first delay addition signal and outputting the delayed output;
an input/output terminal for outputting the output of the first delay addition circuit;
a reference input/output terminal for outputting the output of the first logic circuit;
a second delay addition circuit for delaying an inputted signal by an amount of delay in accordance with a second delay addition signal and outputting the delayed signal; and
a second logic circuit for outputting an operation pattern output signal in accordance with two input signals, wherein
the second delay addition circuit receives the output of the first logic circuit which has been looped back from the reference input/output terminal and
the second logic circuit receives the output of the first delay addition circuit which has been looped back from the input/output terminal and receives the output of the second delay addition circuit.
2. The semiconductor integrated circuit of claim 1 , further comprising:
a self-diagnostic circuit for generating the operation pattern input signal in response to a pattern generation start signal, receiving a delay setting signal indicative of a delay setting condition which is the respective amounts of delay to be added by the first delay addition circuit and the second delay addition circuit, generating the first delay addition signal and the second delay addition signal in accordance with the delay setting condition, determining whether or not the operation pattern output signal is a desired signal corresponding to the operation pattern input signal, and outputting a result of the determination.
3. The semiconductor integrated circuit of claim 2 , further comprising: a self-diagnosis control circuit for generating the pattern generation start signal and the delay setting signal to control the self-diagnostic circuit such that the self-diagnostic circuit makes the determination under a plurality of the delay setting conditions.
4. The semiconductor integrated circuit of claim 3 , wherein the self-diagnosis control circuit stores the results of the determination outputted from the self-diagnostic circuit in association with the delay setting conditions.
5. The semiconductor integrated circuit of claim 4 , wherein the self-diagnosis control circuit controls the self-diagnostic circuit such that the self-diagnostic circuit makes the determination a specified number of times under the same delay setting condition.
6. The semiconductor integrated circuit of claim 5 , further comprising; an analytic determination circuit for analyzing a range of a jitter based on a number of times that the operation pattern output signal has been the desired signal corresponding to the operation pattern input signal and on the delay setting condition, determining whether or not a result of the analysis falls within a specified range in accordance with specifications, and outputting a result of the determination.