SRAM timing test circuit and test method

Abstract

The invention discloses a SRAM timing sequence test circuit and a test method. The test circuit comprises a SRAM memory cell and a test circuit unit. The test circuit unit comprises a first mode switching circuit connected with the SRAM memory cell, an edge signal trigger circuit connected with the first mode switching circuit and a second mode switching circuit connected with the edge signal trigger circuit. The first mode switching circuit has a first enable pin. The second mode switching circuit has a second enable pin. According to signal control difference of the first and second enable pins, a first annular oscillating circuit and a second annular oscillating circuit are respectively formed in the test circuit; and output oscillation periods of the two annular oscillating circuits are measured so as to accurately obtain time value of reading data of the SRAM memory cell. The test circuit provided by the invention can be completed by an automatic wiring tool, and has advantages of small measuring error, high precision and simple measurement.

Description

technical field [0001] The invention relates to the unit circuit field of a static random access memory (SRAM), in particular to a timing test circuit and a testing method for testing timing index parameters of the SRAM. Background technique [0002] After the semiconductor technology enters the deep sub-micron era, the chip can work at a frequency of several hundred MHz or upper GHz, and the working frequency of its internal SRAM may be higher. However, in chip testing, due to the impact of packaging and testing equipment, the clock signal provided by external testing can only reach a frequency of tens or at most 100 MHz. [0003] In the aforementioned context, today's chip testing generally relies heavily on built-in self-test (BIST) circuits. The advantage of BIST circuits is not only the automation of testing, but also high-speed testing because no external testing paths are required. The BIST circuit of the SRAM is also called the memory built-in self-test (MBIST) circ...

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Problems solved by technology

[0005] However, the disadvantages of this circuit are: (1) It involves more manual layout design, which consumes more time and is less efficient. For example, in order to ensure the accuracy of Tcq measurement, the delay circuit ID0 needs to be completed manually, otherwise it will be generated by automatic layout and routing tools. The circuit layout delay has great uncertainty, which causes the accuracy of Tcq measurement to be uncontrollable; (2) The accuracy of Tcq measurement is low. For example, the measurement of Tcq by delay unit Delay1 fails, but the measurement of Tcq by delay unit Delay2 succeeds, then Tcq Between the delay time of Delay1 and the delay time of Delay2, the minimum measurement error is the difference between the two delay times; (3) The process of measuring Tcq is cumbersome, and it is necessary to continuously adjust Delay_Sel until the output data of the SRAM is correctly latched

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