LDO Odometer Circuit for Recycled IC Detection
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Solution Overview
Problem
Current methods for detecting counterfeit integrated circuits (ICs) are inadequate for analog and mixed signal (AMS) circuits, as existing hardware security primitives are primarily developed for digital ICs and do not meet the stringent constraints of area, power, pins, and clock requirements for AMS chips, posing a reliability threat in critical systems.
Innovation Solution
A low dropout regulator (LDO) design with a custom odometer capability, featuring a reference path and a stressed path, where the stressed path ages under normal operation while the reference path remains low-stress, allowing for accurate detection of recycled ICs by monitoring LDO parameter changes when switching between paths.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If existing hardware security primitives (such as PUFs and ring oscillator-based odometers) are used for counterfeit detection, then detection capability is provided, but area, power, pins, and clock constraints are violated for AMS circuits
Solution Approach 1:
The LDO circuit is designed to perform dual functions: normal voltage regulation and counterfeit detection. The same LDO circuitry (error amplifier, pass transistor, resistor divider) is used for both power regulation and sensing aging effects, eliminating the need for separate detection hardware and thus satisfying area, power, pin, and clock constraints while maintaining detection capability
Solution Approach 2:
The invention merges the counterfeit detection functionality with the existing LDO power regulation circuit. By combining the reference path and stressed path within the same LDO structure and using the existing error amplifier and feedback network for both regulation and detection, the solution reduces overall device complexity while providing reliable counterfeit detection
2Measurement precision
If a stressed RO is designed to age rapidly for detection, then sensitivity to recycling is improved, but the reference RO must remain stable which increases design complexity
Solution Approach 1:
The invention applies local quality by creating asymmetric aging conditions within the LDO circuit. The pass transistor in the feedback path is subjected to high stress (high Vgs and Vds) during normal operation, causing it to age and drift. This localized stress application to a specific component within the LDO provides sensitivity to recycling without requiring a separate reference circuit, thereby reducing design complexity
Solution Approach 2:
The LDO circuit uses its own operational characteristics to create the aging effect. During normal voltage regulation operation, the pass transistor naturally experiences high stress conditions that accelerate aging. The circuit essentially ages itself through its normal function, eliminating the need for external aging mechanisms or complex reference-stressed path designs while maintaining measurement precision
3Measurement precision
If LDO parameters are monitored to detect recycling, then counterfeit detection accuracy is improved, but the LDO must operate in specific regions which limits design flexibility
Solution Approach 1:
The invention employs dynamic operation of the LDO circuit, utilizing the fact that the pass transistor operates in different regions (linear and saturation) during normal regulation. The aging effect is most pronounced when the transistor operates in specific regions, and the circuit naturally transitions between regions during operation. This dynamic operation allows the circuit to accumulate aging effects while maintaining regulation functionality, achieving both detection accuracy and design flexibility
Data Source
AI summary
A method and system are directed to designing a low-dropout regulator (LDO) circuit and using the LDO circuit to detect recycled counterfeit integrated circuits. The LDO circuit includes, in part, a reference path circuit and a stressed path circuit. Each of the reference path circuit and the stressed path circuit is coupled to a control signal that can enable the corresponding path circuit for the LDO. LDO parameters can then be measured while the reference path circuit and the stressed path circuit is enabled respectively. The difference between the LDO parameters measured while the reference path circuit is enabled and while the stressed path circuit is enabled is used to determine if an integrated circuit comprising the LDO circuit is a recycled counterfeit.