Flash Memory High Voltage Generator Ripple Reduction
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Solution Overview
Problem
Conventional high voltage generator circuits for flash memory devices experience undesired voltage ripple due to continued pumping operations beyond the target level, leading to instability and inefficiency in program voltage generation.
Innovation Solution
A high voltage generator circuit with a clock modification circuit that adjusts the pumping slope by modifying the pulse width, frequency, or amplitude of the pumping clock signal once the program voltage reaches its target level, reducing the pumping slope and thereby minimizing voltage ripple.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the charge pump continues pumping after the program voltage reaches the target level, then the voltage generation process is simple and continuous, but voltage ripple occurs and stability deteriorates
Solution Approach 1:
The patent implements a feedback mechanism where the comparison result from comparing the program voltage with a reference voltage is fed back to the clock modification circuit. This feedback loop allows the system to automatically adjust the pumping clock signal based on the actual voltage level, stopping the charge pump when the target voltage is reached, thereby eliminating voltage ripple while maintaining a relatively simple control structure.
Solution Approach 2:
The patent dynamically adjusts the pumping clock signal characteristics (frequency, duty cycle, or amplitude) based on the comparison result. The clock modification circuit changes the clock signal parameters in real-time according to whether the program voltage has reached the target level, enabling the system to adapt its operation to maintain stability without requiring complex control logic.
2Reliability
If the charge pump stops immediately when the target voltage is reached, then voltage stability improves, but voltage ripple may occur due to abrupt cessation
Solution Approach 1:
The patent prepares the clock modification circuit and comparison mechanism in advance so that when the program voltage approaches the target level, the system can smoothly transition from pumping to non-pumping mode. The preliminary setup of the feedback loop and clock modification capability allows for a controlled reduction of pumping activity rather than abrupt cessation, preventing voltage ripple while maintaining stability.
3Device complexity
If a feedback loop with RC delay is used to control the charge pump, then the control mechanism is simple, but a delay period occurs causing the voltage to exceed the target level and creating ripple
Solution Approach 1:
The patent extracts and eliminates the problematic RC delay element from the feedback loop. By removing the delay mechanism and using direct feedback comparison, the system can respond immediately when the program voltage reaches the target level, preventing over-voltage conditions and voltage ripple while maintaining a simple control structure without requiring complex delay compensation circuits.
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 stabilizes the program voltage generation, reduces voltage ripple, and simplifies the circuit structure, enabling high-speed and efficient operations in flash memory devices.
Implementation Method 1
a charge pump generating a high voltage in response to a pumping clock signal
Implementation Method 2
a charge/discharge circuit responsive to the pumping clock signal and charging the high voltage to generate an output voltage
Implementation Method 3
a comparator for comparing the output voltage with a reference voltage to generate a comparison result
Data Source
AI summary
A high voltage generator includes a charge pump generating a high voltage in response to a pumping clock signal, a charge/discharge circuit responsive to the pumping clock signal and charging the high voltage to generate an output voltage, a comparator for comparing the output voltage with a reference voltage to generate a comparison result, and a clock modification circuit adjusting a pumping slope of the charge pump in relation to the comparison result, wherein the clock modification circuit reduces the pumping slope when the high voltage reaches a target voltage level.