Power Supply Circuit Ripple Reduction in Semiconductor Memory
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Solution Overview
Problem
Conventional power supply circuits for semiconductor memories, such as NAND flash memories, experience increased ripples in output potential during writing operations, leading to expanded Vth distribution and erroneous writing on unselected cells, due to the dependence of boosting capability on set potential and the use of voltage dividing resistors.
Innovation Solution
A power supply circuit that adjusts reference potentials and clock frequencies based on control signals, using a voltage detecting circuit, clock generating circuit, and logic circuit to optimize the boosting clock signal, thereby reducing ripple dependence on set potential and enhancing boosting capability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If voltage dividing resistors with large resistance are used in the voltage detecting circuit, then the circuit complexity is reduced, but ripples increase due to operation delay and reduced boosting capability
Solution Approach 1:
The patent applies dynamics by making the voltage detecting circuit adjustable through control signals. The voltage dividing resistors can be dynamically configured to different resistance values based on operating conditions, allowing the circuit to adapt between complexity and performance requirements. This resolves the contradiction by enabling the system to use simpler resistor configurations when stability is less critical and more complex configurations when precision is needed.
Solution Approach 2:
The patent changes the resistance parameter of the voltage dividing resistors based on control signals. By dynamically adjusting the resistance values of the voltage dividing resistors, the system can optimize the balance between circuit complexity and ripple suppression. This parameter change allows the same hardware to operate in different modes, resolving the contradiction between simplicity and stability.
2Adaptability or versatility
If the set potential of the voltage detecting circuit is lowered to enable writing operations on cells with low potential, then adaptability to different cell potentials is improved, but ripples increase due to higher output current in fixed time periods
Solution Approach 1:
The patent makes the voltage detecting circuit dynamic by allowing the set potential to be adjusted according to the writing operation requirements. When writing to cells with low potential, the circuit dynamically lowers the set potential to enable proper operation. This dynamic adjustment resolves the contradiction by adapting the circuit behavior to the specific writing task while maintaining stability through controlled potential changes.
Solution Approach 2:
The patent applies preliminary action by pre-configuring the voltage detecting circuit with multiple potential levels that can be selected before writing operations. This allows the system to prepare the appropriate set potential in advance based on the target cell characteristics, ensuring stable operation throughout the writing process without unexpected ripple effects.
3Reliability
If the boosting capability is increased to reduce ripples at low set potentials, then output potential stability is improved, but the device complexity increases due to additional control circuits
Solution Approach 1:
The patent applies universality by designing the control circuit to serve multiple functions: it controls both the voltage detecting circuit's set potential and the boosting circuit's operation. This multi-functionality reduces the need for separate dedicated circuits, thereby limiting the increase in device complexity while still achieving improved output potential stability through coordinated control.
Solution Approach 2:
The patent uses feedback by having the voltage detecting circuit continuously monitor the output potential and feed this information back to the control circuit. This feedback mechanism allows the control circuit to dynamically adjust the boosting capability in response to actual ripple conditions, achieving stability improvement through intelligent control rather than complex hardware additions.
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 reduces ripple fluctuations and improves writing accuracy by dynamically adjusting the boosting capability in response to set potentials, minimizing Vth distribution expansion and erroneous writing.
Implementation Method 1
In the boosting circuit, MOS transistors and capacitances are connected in series and one ends of the capacitances are connected via complementary CLK and CLKB signals to boost a power supply voltage
Implementation Method 2
The voltage detecting circuit includes a voltage dividing circuit and a comparator amplifier circuit. The output terminal of the boosting circuit and a ground potential are connected in series via the voltage dividing circuit
Data Source
AI summary
A power supply circuit outputs different set potentials in response to control signals, wherein a voltage detecting circuit changes levels of a first reference potential and a second reference potential in response to inputs of control signals, and a clock generating circuit increases a frequency of the frequency divided clock signal when the levels of the first reference potential and the second reference potential are greatly changed in response to the inputs of the control signals.