Adaptive Word-Line Boost Driver for Embedded Flash Memory
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Solution Overview
Problem
Conventional embedded flash memory designs in micro-controller units suffer from slow word line rise time, which acts as a bottleneck for high-speed read operations, especially under varying power supply conditions.
Innovation Solution
The implementation of an adaptive word line driver and adaptive word line boost driver that quickly pull up the word line voltage to 2.5 V within 1 ns, using a combination of level shifters, decoders, transistors, and a voltage detector to manage voltage levels and optimize word line activation across a wide range of power supplies from 2.5 V to 3.6 V.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If conventional word line driver designs are used, then device complexity is reduced, but word line rise time becomes slow
Solution Approach 1:
The patent implements dynamic word line driving by switching between two operational modes: a first mode using a conventional driver for normal operation, and a second mode using a boost circuit for accelerated rise time. The system dynamically selects the appropriate mode based on operational requirements, achieving fast word line rise time only when needed rather than always, thus balancing speed improvement with circuit complexity management.
Solution Approach 2:
The boost circuit is pre-configured and ready to activate when fast word line rise time is required. The circuit includes pre-charged capacitors and pre-positioned transistors that can immediately begin boosting the word line voltage when activated, rather than requiring gradual charging. This preliminary preparation enables the system to achieve fast rise time on demand without permanently maintaining the complex boost circuitry in an active state.
2Speed
If boost driver is always activated, then word line rise time is fast, but power consumption increases
Solution Approach 1:
The system dynamically activates the boost driver only when fast word line rise time is required, switching between a low-power conventional mode and a high-speed boost mode. This dynamic operation allows the system to achieve fast rise time on demand while minimizing power consumption during normal operation, directly resolving the contradiction between speed and energy usage.
Solution Approach 2:
The boost driver operates periodically or event-driven rather than continuously, activating only when specific conditions require fast word line rise time. This periodic activation pattern allows the system to maintain fast rise time capability when needed while significantly reducing average power consumption compared to continuous boost operation.
3Measurement precision
If voltage detection and adaptive control are added, then voltage control precision is improved, but device complexity increases
Solution Approach 1:
The patent incorporates voltage detection circuits that monitor the actual word line voltage and provide feedback to the control logic. This feedback mechanism enables the system to detect voltage conditions and adaptively adjust the driving mode, achieving precise voltage control by continuously monitoring and responding to actual voltage levels rather than relying on open-loop control.
Solution Approach 2:
The voltage detection and control circuits serve multiple functions: they detect voltage levels, determine appropriate driving modes, control the boost circuit activation, and manage power consumption. By making these circuits multi-functional, the patent reduces the need for separate dedicated circuits for each function, thereby limiting the increase in overall device complexity while still achieving precise voltage control.
Data Source
AI summary
A word line driver circuit includes a first transistor having its gate coupled to a first node configured to receive a word line select signal. A second transistor has its gate coupled to the first node and a drain coupled to a drain of the first transistor at a second node that is coupled to a word line. A word line assist control circuit is coupled to the first node, to the word line, and to a gate of a third transistor. The word line assist control circuit is configured to turn on or turn off the third transistor to adjust a voltage of the word line.