Programmable Reference Current Generator for Memory Sensing Drift
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Solution Overview
Problem
Non-volatile memory cells, such as SONOS cells, face challenges in maintaining reliable data storage across varying temperatures and aging conditions, leading to inadequate noise margin and reduced sensing accuracy due to shifts in output currents, making them unsuitable for industrial and military applications with extended temperature ranges.
Innovation Solution
A trimmable reference current generator is developed, incorporating a proportional to absolute temperature (PTAT) current generation circuit and programmable current scaling circuits to produce a reference current with a predetermined temperature coefficient and dc offset, ensuring accurate sensing over a wide temperature range and accounting for process variations and aging effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a fixed reference current is used for memory sensing, then the circuit is simple and easy to manufacture, but the sensing accuracy deteriorates over temperature and aging
Solution Approach 1:
The reference current generator is made dynamically adjustable through programmable current scaling circuits that can modify the reference current magnitude based on temperature conditions and aging characteristics, allowing the system to adapt to changing environmental and temporal factors while maintaining sensing accuracy
Solution Approach 2:
The invention changes the parameter of reference current by introducing temperature coefficients and programmable scaling factors. The reference current is no longer fixed but varies according to temperature and programmable parameters, enabling compensation for temperature drift and aging effects without requiring complex external calibration
2Adaptability or versatility
If the temperature range is extended for industrial and military applications, then the adaptability improves, but the noise margin becomes inadequate
Solution Approach 1:
The reference current generator incorporates temperature coefficient programming that allows the output current to vary systematically with temperature. By programming appropriate temperature coefficients, the system maintains adequate noise margin across extended temperature ranges from -55°C to +125°C, enabling reliable operation in industrial and military applications
Solution Approach 2:
The system dynamically adjusts the reference current characteristics based on temperature conditions through programmable scaling circuits. This dynamic adaptation ensures that the noise margin remains sufficient across the entire extended temperature range, preventing the reliability degradation that would occur with a fixed reference current
3Duration of action of stationary object
If the memory cell ages or undergoes programming cycles, then the memory maintains data storage capability, but the output current shifts
Solution Approach 1:
The programmable current scaling circuits provide a form of feedback compensation by allowing the reference current to be adjusted based on observed shifts in memory cell characteristics. As the memory ages or undergoes programming cycles, the scaling parameters can be modified to compensate for current shifts, maintaining measurement accuracy throughout the memory's operational lifetime
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution provides a highly accurate reference current for memory sense amplifiers, maintaining sufficient sensing margin across a wide temperature range and during memory cell degradation, enhancing the reliability of non-volatile memory systems in extreme temperature applications.
Implementation Method 1
a proportional to absolute temperature (PTAT) current generation circuit
Data Source
AI summary
In accordance with an embodiment, a circuit includes: a trimmable reference current generator having a temperature dependent current output node, the trimmable reference current generator including: a proportional to absolute temperature (PTAT) current generation circuit; a first programmable current scaling circuit coupled to the PTAT current generation circuit and including a first output coupled to the temperature dependent current output node; a constant current generation circuit; a second programmable current scaling circuit coupled to the constant current generation circuit and including a first output coupled to the temperature dependent current output node; and a reference interface circuit having an input coupled to the temperature dependent current output node and an output configured to be coupled to a reference current input of a memory sense amplifier.