Temperature and voltage measurement for field test using an Aging-Tolerant monitor

Measuring temperature and voltage (T&V) in a current VLSI is very important in guaranteeing its reliability, because a large variation of temperature or voltage in field will reduce a delay margin and makes the chip behavior unreliable. This paper proposes a novel method of T&V measurement, which can be used for variety of applications, such as field test, online test, or hot-spot monitoring. The method counts frequencies of more than one ring oscillator (RO), which composes an aging-tolerant monitor. Then, the T&V are derived from the frequencies using a multiple regression analysis. To improve the accuracy of measurement, three techniques of an optimal selection of RO types, their calibration, and hierarchical calculation are newly introduced. In order to make sure the proposed method, circuit simulation in 180-, 90-, and 45-nm CMOS technologies is performed. In the 180-nm CMOS technology, the temperature accuracy is within 0.99 °C, and the voltage accuracy is within 4.17 mV. Furthermore, some experimental results using fabricated test chips with 180-nm CMOS technology confirm its feasibility

Temperature and Voltage Estimation Using Ring-Oscillator-Based Monitor for Field Test

Field test is performed in diverse environments, in which temperature varies across a wide range. As temperature affects a circuit delay greatly, accurate temperature monitors are required. They should be placed at various locations on a chip including hot spots. This paper proposes a flexible ring-oscillator-based monitor that accurately measures voltage as well as temperature at the same time. The measurement accuracy was confirmed by circuit simulation for 180 nm, 90 nm and 45 nm technologies. An experiment using test chips with 180 nm technology shows its feasibility.2014 IEEE 23rd Asian Test Symposium (ATS), 16-19 Nov. 2014, Hangzhou, Chin

Reduction of NBTI-Induced Degradation on Ring Oscillators in FPGA

Ring Oscillators are used for variety of purposes to enhance reliability on LSIs or FPGAs. This paper introduces an aging-tolerant design structure of ring oscillators that are used in FPGAs. The structure is able to reduce NBTI-induced degradation in a ring oscillator\u27s frequency by setting PMOS transistors of look-up tables in an off-state when the oscillator is not working. The evaluation of a variety of ring oscillators using Altera Cyclone IV device (60nm technology) shows that the proposed structure is capable of controlling degradation level as well as reducing more than 37% performance degradation compared to the conventional oscillators.The 20th IEEE Pacific Rim International Symposium on Dependable Computing (PRDC 2014), Nov 19-21, 2014, Singapor

On-chip delay measurement for in-field test of FPGAs

Avoidance of delay-related failures due to aging phenomena is an important issue of current VLSI systems. Delay measurement in field is effective for detection of aging-induced delay increase. This paper proposes a delay measurement method using BIST (Built-In Self-Test) in an FPGA. The proposed method consists of variable test timing generation using an embedded PLL, BIST-based delay measurement, and correction of the measured delay with reflecting temperature variance in field. In on-chip delay measurement of the proposed method, the fastest operating speed is checked by repeating delay test with several test timings. Because circuit delay is influenced by temperature during measurement, the measured delay is then corrected according to the temperature during testing. Based on test log including the corrected delay, delay degradation and aging detection can be grasped. In evaluation experiments of the propose method implemented on an Intel Cyclone IV FPGA device (60nm technology), variable test timing generation realized 96 ps timing step resolution (that is below 1% of the system clock), correction process for measured delay could reduce influence of temperature variation. Furthermore, its feasibility of the proposed method for aging detection is discussed in this paper.24th IEEE Pacific Rim International Symposium on Dependable Computing (PRDC 2019), December 1-3, 2019, Kyoto, Japa

Path Delay Measurement with Correction for Temperature And Voltage Variations

Path delay measurement in field is useful for not only detection of delay-related faults but also prediction of aging-induced delay faults. In order to utilize the delay measurement results for fault detection and fault prediction, the measured delay must be corrected because the circuit delay is varied in field due to environment such as temperature or voltage variations. This paper proposes a method of BIST-based path delay measurement in which the influence of environmental variations is eliminated. An on-chip sensor measures temperature and voltage during delay measurement. Using information from the temperature and voltage sensor and pre-computed temperature and voltage sensitivities of the circuit delay, the measured delay value is corrected to a delay value that would be obtained under a fixed temperature and voltage. Evaluation for a test chip with 65nm CMOS technology implementing the proposed method shows that errors of measured delays brought by environmental variations could be reduced from 2419 to 211 ps in the range of 30 to 80 °C and 1.05 to 1.35 V. This paper also discusses application and feasibility for degradation detection of the proposed method.International Test Conference in Asia (ITC-Asia 2020), September 23-25, 2020, Taipei City, Taiwan（現地およびオンラインで開催

A selection method of ring oscillators for an on-chip digital temperature and voltage sensor

An on-chip digital sensor using three types of ring oscillators (ROs: Ring Oscillators) has been proposed to measure temperature and voltage of a VLSI. Each RO has inherent frequency characteristics with respect to temperature and voltage, which differ from those of the other two ROs. Measurement accuracy of the sensor depends on the combination of the ROs. This paper proposes a RO-selection method for the sensor with high accuracy. The proposed method takes particular note of temperature or voltage sensitivity as well as linearity of the RO characteristics. Evaluation experiments with SPICE simulation in 65 nm CMOS technology show that the temperature and voltage accuracies of the sensor are 2.744°C and 3.825mV, respectively, and the selected combination was a nearly optimal from a menu of many different ROs.The 3rd International Test Conference in Asia (ITC-Asia 2019), September 3-5, 2019Tokyo Denki University, Tokyo, Japa

On-chip test clock validation using a time-to-digital converter in FPGAs

While on-chip delay measurement combining logic BIST with a variable test clock is an effective way to secure field reliability of VLSI/FPGAs, validation of the variable test clock generated on the chip is important to guarantee measurement accuracy. This paper addresses a method of on-chip test clock validation using a TDC (Time-to-Digital Converter) for FPGAs. The proposed method has two operation modes, one is a resolution measurement mode and the other is a phase difference measurement mode. The resolution measurement mode is performed first to check the resolution of the TDC circuit. The phase difference measurement mode checks the timing difference between the original clock and the generated test clock. Evaluation experiments using a real FPGA device shows that the resolution of the proposed clock validation method using a TDC is 50.46 ps. For a variable test clock with resolution of 96.15 ps, it was confirmed that INL (Integral Non-Linearity) of the clock is within 10% and it was inconsistent with a result observed by an oscilloscope.The 3rd International Test Conference in Asia (ITC-Asia 2019), September 3-5, 2019Tokyo Denki University, Tokyo, Japa

On Evaluation for Aging-Tolerant Ring Oscillators with Accelerated Life Test and Its Application to A Digital Sensor

An aging-tolerant ring oscillator (RO) has been proposed for a digital temperature and voltage sensor. This paper discusses on the effectiveness of aging-tolerance of the ROs through accelerated life test for a test chip with 65nm CMOS technology. The progress of delay degradation of the ROs is examined, and influence of delay degradation on measurement accuracy of the sensor is investigated. Experimental results show that the aging-tolerant ROs can mitigate delay degradation, and that the measurement errors of the sensor can be reduced. Compared with a sensor consisting of an aging-intolerant RO, temperature and voltage errors are reduced 2.5°C and 32mV, respectively.29th IEEE Asian Test Symposium (ATS\u2720), November 22-25, 2020, Penang, Malaysia（オンライン開催に変更

Life sciences

Aims: To examine the circadian expression changes in bladder clock genes in Dahl salt-sensitive rats following high salt intake. Main methods: Eighteen rats were divided into three groups: the high-salt diet group (HS group), the normal-salt diet group (NS group), and the salt-load interruption group (from a 4 % salt diet to a normal diet; salt-load interruption group [SI group]). Each rat was placed in an individual metabolic cage for 24 h twice weekly. Water intake, urine production, voiding frequency, and voided volume per micturition were recorded. Furthermore, 108 control rats were prepared. Bladders were harvested every 4 h at six time points. Furthermore, the mRNA expression of clock genes and mechanosensors was analyzed. Key findings: In the HS group, the bladder clock genes showed lower mRNA levels than in the NS group. The amplitude of circadian expression changes in bladder clock genes in the HS group was lower than that in the NS group. However, after changing from a 4 % salt diet to a normal diet, the waveforms of the clock gene expression in the SI group were closer to those of the NS group. The 24-h water intake and urinary volume of the SI group decreased to levels comparable to those of the NS group. Significance: Reduced salt intake partially restored the circadian rhythms of bladder clock genes.博士（医学）・甲第857号・令和4年12月22日Copyright © 2022 Elsevier Inc. All rights reserved

On-Chip Delay Measurement for Degradation Detection and Its Evaluation under Accelerated Life Test

Periodical delay measurement in field is useful for not only detection of delay-related faults but also prediction of faults due to aging. Logic BIST with variable test clock generation enables on-chip delay measurement in field. This paper addresses a delay measurement scheme based on logic BIST and gives experiment results to observe aging phenomenon of test chips under accelerated life test. The measurement scheme consists of scan-based logic BIST, a variable test clock generator, and digital temperature and voltage sensors. The sensors are used to compensate measured delay values for temperature and voltage variations in field. Evaluation using SPICE simulation shows that the scheme can measure a circuit delay with resolution of 92 ps. The delay measurement scheme is also implemented on fabricated test chips with 180 nm CMOS technology and accelerated test is performed using ATE and burn-in equipment. Experimental results show that a circuit delay increased 552 ps when accelerated the chip for 3000 hours. It is confirmed that the on-chip delay measurement scheme has enough accuracy for detection of aging-induced delay increase.26th IEEE International Symposium on On-Line Testing and Robust System Design (IOLTS 2020), 13-15 July, 2020, Napoli, Italy（新型コロナ感染拡大に伴い、オンライン開催に変更