Defects can occurs during the manufacturing process. They are defined according to the degree of faulty effects, to simplify fault modeling and fault simulation efforts. Two categories of fault models are considered hard fault and soft fault. Also no as such acceptable fault model is available. Because of the wide range of analog and AMS circuits, no as such simple and effective fault model is available for them. In industry SSF model is widely used fault model for digital ICs. Single Stuck_at Faults (SSF) are simple and effective. Mixed signals are quantization of analog signals. Also digital signals are mostly binary, with VDD for logical high and GND for logical low. Digital signals are discrete in both domains. Both in time and amplitude domains, the analog signals are continuous. Paper is concluded in section FAULT MODELS Continuance and discreteness fundamentally distinguish analog from digital signals. Basics of DAC and the simulation carried out for DAC are described in section 3. The paper is arranged as follows, section 2 describes the fault models for analog circuits. The simulation of 3-bit R-2R DAC for various transistor stuck_open and stuck _short are carried out. This paper also discusses the performance parameter of R-2R DAC and its CMOS implementation using 350nm technology. In this paper, the fault models for AMS circuit is discussed. Simulation-after-test approaches begin with the failed responses, which are then used to estimate faulty parameter or component values. Faults are consequently diagnosed by comparing simulated and observed responses. The faults are then simulated to determine the corresponding responses to predetermined stimuli. Simulation-before-test approaches begin with a fault list. Simulation-before-test and simulation-after test, these two strategies were proposed in.
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DOI : /vlsicĢ Analog and AMS circuit testing can be perform in two ways Simulation before test and simulation after test. This makes the design and manufacturing of the tester really a challenge and introduces high test costs. Measurement equipment with high precision than the Device under Test (DUT) is required in conventional DAC test to characterize the performance of the DUT.
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Test of data converters like ADC and DAC is most challenging problems in testing of AMS circuit test. The DAC is one of the most widely used mixed-signal integrated circuits as an interface between digital processing systems.
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Analog to Digital Converter (ADC), Digital to Analog Converter (DAC) and Phase Locked Loop (PLL) are the examples of AMS circuits. Also the reliability and performance of AMS circuits can be degraded due to sensitivity to small imperfections during the steps of the fabrication process and high integration density. Testing of these AMS circuits can become limiting factor in contributing to manufacturing cost. Limited controllability and observability increases the testing efforts of these AMS circuits. AMS testing strongly depends on circuits. SoC consisting analog and mixed signals brings lots of challenges in testing. In last few decades the testing of digital ICs are fully explored. Wide range of AMS circuits are available. INTRODUCTION Nowadays System on Chip (SoC) contains analog and mixed-signal (AMS) circuits. KEYWORDS Stuck_open, Stuck_short, testing, DAC, fault.
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Further these fault models are used to analyze the effects on the characteristics parameter of 3-bit R-2R DAC. SAF (stuck_at_fault), Stuck_open and stuck_short fault model at transistor level is used in this paper. Testing of analog and mixed signals faces lots of challenges due to the wide range of circuits and unavailability of one appropriate fault model. 1 SAF ANALYSES OF ANALOG AND MIXED SIGNAL VLSI CIRCUIT: DIGITAL TO ANALOG CONVERTER ABSTRACT Vaishali Dhare 1 and Usha Mehta 2 1 Assistant Professor, Institute of Technology, Nirma University, Ahmedabad 2 Senior Member, IEEE, Professor, Institute of Technology, Nirma University, Ahmedabad Digital to analog converter is widely used mixed-signal circuit.