Charge Pump Fault Detection via Tank Capacitor Charging Time
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Solution Overview
Problem
Existing charge pumps in non-volatile memory circuits are vulnerable to attacks that disrupt the normal functioning, leading to incorrect operations due to inaccurate voltage provision, and there is a need to detect such attacks to ensure secure data storage.
Innovation Solution
A charge pump with a detection circuit that measures the charging time between minimum and maximum regulation voltages, triggering an alarm signal if the time exceeds a threshold, using a phase generator, regulator circuit, and detection circuit with a counter and comparator to monitor voltage regulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a charge pump is used to provide high voltages for non-volatile memory operations, then the memory can perform erasing, writing, and reading operations, but the charge pump becomes a vulnerable target for fault attacks that can disrupt voltage regulation and cause incorrect operations
Solution Approach 1:
The patent applies preliminary action by measuring the charging time of the tank capacitor before memory operations are executed. The detection circuit continuously monitors the time required to charge the tank capacitor from minimum to maximum regulation voltage. If the charging time exceeds a predetermined threshold, indicating a potential fault attack, the system raises an alarm signal and prevents the memory operation from proceeding, thus preventing incorrect operations before they occur.
Solution Approach 2:
The patent implements feedback by using the measured charging time as a feedback parameter to monitor the health of the charge pump. The detection circuit measures the charging time and compares it against a threshold value, creating a closed-loop monitoring system. This feedback mechanism allows the system to detect abnormalities in real-time and respond appropriately by raising an alarm signal when the charging time indicates a potential attack or malfunction.
2Reliability
If the charging time of the tank capacitor is not monitored, then the charge pump operates without detection circuits, but attacks can go undetected leading to incorrect memory operations
Solution Approach 1:
The patent applies segmentation by separating the detection function from the charge pump operation. The detection circuit is implemented as a distinct module with its own counter and comparator circuits, independent from the main charge pump control logic. This segmentation allows the detection function to be added without fundamentally redesigning the charge pump architecture, and the detection circuit can be selectively enabled or disabled based on security requirements.
Solution Approach 2:
The patent uses an intermediary approach by introducing a detection circuit that acts as a mediator between the charge pump and the memory operation. The detection circuit measures charging time and provides alarm signals without directly interfering with the charge pump's voltage generation function. This intermediary layer adds security monitoring capability while maintaining the independence and functionality of the original charge pump circuit.
3Reliability
If a detection circuit with counter and comparator is added to measure charging time, then attacks can be detected, but the charge pump circuit complexity increases
Solution Approach 1:
The patent applies universality by designing the detection circuit to serve multiple functions. The same counter circuit that measures charging time can also function as a general-purpose timer or frequency counter for other monitoring purposes. The comparator circuit can be configured to monitor multiple different parameters by changing reference values. This multi-functionality reduces the need for separate dedicated circuits for each monitoring function, thereby reducing overall complexity.
Solution Approach 2:
The patent uses parameter changes to simplify the detection circuit implementation. Instead of using complex analog monitoring circuits, the invention converts the voltage monitoring problem into a time measurement problem by measuring the charging time of the capacitor. This parameter transformation allows the use of simple digital counter and comparator circuits rather than complex analog voltage monitoring circuits, reducing overall circuit complexity while maintaining detection capability.
Data Source
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AI summary
The invention relates to a charge pump comprising a tank capacitor (CT) filled by at least one pumping stage (310) which is driven by a phase generator (320) controlled by a regulator circuit (330) connected to said tank capacitor (CT). The regulator circuit (330) provides a control signal (REGOK) in an active or inactive state for activating or for stopping the phase generator as a function of the voltage of the tank capacitor. The charge pump circuit further comprises a measuring circuit (351) and a comparator circuit (352). The measuring circuit (351) receives the control signal (REGOK) and provides a time value indicating the time since the last triggering of the control signal (REGOK) into the active state. The comparator circuit (352) is connected to measuring circuit (351) and provides an alarm signal (ALARM) when the time value is higher than a threshold value (Tmax).