Adaptive Voltage Scaling Circuit for Gate Delay Variation Sensing
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Solution Overview
Problem
Existing AVS techniques face challenges in accurately detecting and correcting both variability and uncertainty in gate delay, particularly due to resource limitations in circuit scale and evaluation time, and the need for complex statistical calculations that are often performed externally, which can hinder dynamic adaptive voltage scaling.
Innovation Solution
The implementation of separate measurement circuits for variability and uncertainty within the semiconductor chip, using ring oscillators and counters to produce relative values that allow for accurate on-chip detection and control of supply voltage, with reference to table data for efficient processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If separate measurement circuits for variability and uncertainty are implemented on the chip, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent divides the measurement function into two separate circuits: a first measurement circuit for variability (inter-die variation) and a second measurement circuit for uncertainty (intra-die variation). Each circuit is optimized for its specific measurement target, with the first circuit using a single ring oscillator and the second circuit using multiple ring oscillators to measure standard deviation. This segmentation resolves the contradiction by improving measurement precision through specialized circuits while managing complexity through functional separation rather than a single complex circuit.
Solution Approach 2:
Both measurement circuits use ring oscillators as the core measurement element, providing a universal approach to gate delay measurement. The ring oscillator structure serves multiple purposes: measuring mean gate delay in the first circuit and measuring gate delay variations in the second circuit. This multi-functionality reduces overall device complexity by reusing a proven measurement topology rather than developing entirely separate measurement mechanisms.
2Use of energy by moving object
If AVS technique is applied to correct process variations, then power consumption is reduced, but manufacturing precision requirements increase
Solution Approach 1:
The patent implements a feedback-based AVS system where measurement circuits continuously monitor gate delay variations caused by process variations, and control circuits adjust supply voltage accordingly. The system measures variability and uncertainty separately, then uses this information to dynamically adjust voltage levels to compensate for process variations. This feedback mechanism reduces power consumption by optimizing voltage levels while accommodating manufacturing variations rather than requiring tighter process control.
Solution Approach 2:
The system changes the supply voltage parameter dynamically based on measured process variations. By adjusting voltage levels according to actual chip characteristics (measured through the measurement circuits), the system compensates for manufacturing variations in gate delay. This approach allows standard manufacturing processes to produce chips with varying characteristics, then uses parameter adjustment (voltage scaling) to achieve uniform performance, thereby reducing power consumption without demanding higher manufacturing precision.
3Measurement precision
If multiple measurement circuits are provided for detecting variability and uncertainty, then measurement precision is improved, but ease of operation deteriorates
Solution Approach 1:
The measurement circuits are designed to automatically perform their respective measurement functions without requiring complex external control. The first measurement circuit autonomously measures variability by comparing its ring oscillator frequency to a reference, while the second measurement circuit autonomously measures uncertainty using multiple ring oscillators. The control circuits automatically process the measurement results and adjust supply voltage accordingly. This self-service operation simplifies the user interface while maintaining high measurement precision through specialized circuits.
Data Source
AI summary
AVS (Adaptive Voltage Scaling) technique, by which variability and uncertainty are both taken into account. In the system arranged for AVS technique, a detection circuit optimum for each type of process variation is set. Examples of the detection circuit so arranged include a first measurement circuit for detection of variability, which produces a relative value with respect to the gate delay mean value, and a second measurement circuit for detection of uncertainty, which produces a relative value related to the gate delay standard deviation. The first and second measurement circuits are provided separately from each other. The control information for deciding the supply voltage is prepared based on relative values produced by the detection circuits. When preparing the control information, reference is made to e.g. a table data.