Error Detection of Data Conversion in Flash ADC using Code Width Based Technique

The high integration density of the complex electronic system requires the multi-functional testing facility to ensure the accuracy of the circuit function. In addition, the wide population of submicron technologies results in the persistent requirements of high precision analog and mixed-signal (AMS) circuits. In the complex, high-density circuits, observing the correctness of output are limited due to the limitations of input and output pins which develop the AMS circuit test as very difficult and expensive. A digital built-in self-test (BIST) scheme has been presented in this paper for testing an analog to digital converter (ADC) in the time domain. The testing scheme consists of the linear analog ramp generator, ADC as a circuit under test, output response analyzer and a BIST controller. Bootstrap linear ramp generator is used to generate the linear analog ramp signal which is applied to ADC to develop the digital word sequence for testing. Among various types of ADCs, here a Flash ADC has used since it is fastest and accurate in digital conversion. A Flash ADC has been designed with the seven-bit resolution and tested using the proposed digital BIST scheme. The ADC comprises a sample-hold circuit, 2(N)-1 comparator, XOR gates, and encoder block. The output response analyzer verifies the digital output sequence to validate the static test parameters of ADC called monotonicity, missing codes, DNL, and INL error. The BIST controller generates the control signals to control the test sequence. The complete test sequence of ADC BIST has simulated in Tanner EDA with TSMC 0.18um technology. ORA is used to analyze the presence of monotonicity, missing codes, DNL and INL error in the ADC output. (C) 2019 The Authors. Published by Elsevier B.V.