Voltage Generating Circuit Charge Sharing Transfer Efficiency
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Solution Overview
Problem
Conventional voltage generating circuits for semiconductor memory devices face inefficiencies in low-voltage driving due to the voltage level at the gate node of the transfer transistor being lower than the boosted voltage level, especially when the power supply voltage decreases or the target boosted voltage increases, which reduces voltage generation efficiency.
Innovation Solution
A voltage generating circuit that includes a multi-boosting unit, a transfer transistor, and a charge-sharing element, where the charge-sharing element is connected to the final boosting node and the gate node of the transfer transistor, enabling charge sharing during the power supply voltage stepping-up period to increase the voltage level at the gate node and enhance transfer efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a conventional transfer transistor is used to output boosted voltage, then the circuit structure is simple, but the voltage level at the gate node is lower than the boosted voltage level, reducing transfer efficiency
Solution Approach 1:
A charge-sharing element is introduced as an intermediary component between the boosting node and the gate node of the transfer transistor. This element enables charge sharing during the boosting process, allowing the gate node to reach higher voltage levels without requiring a more complex transistor structure. The charge-sharing element acts as a mediator that transfers charge from the boosting node to the gate node, resolving the contradiction between simple structure and high transfer efficiency.
Solution Approach 2:
The charge-sharing element is enabled during the boosting process to perform charge sharing before the transfer transistor operates. By pre-charging the gate node during the boosting phase, the system prepares the transfer transistor with adequate gate voltage in advance, improving transfer efficiency without adding complexity to the main transistor structure.
2Productivity
If the power supply voltage decreases or target boosted voltage increases, then the voltage generation requirement becomes more stringent, but the gate node voltage becomes even lower relative to the boosted voltage, significantly reducing transfer efficiency
Solution Approach 1:
The charge-sharing element serves as a critical intermediary that becomes increasingly important as operating conditions become more challenging. Under low Vcc or high target Vpp conditions, the charge-sharing element enables the gate node to capture a larger portion of the boosted voltage, maintaining reliable transfer characteristics even when the voltage margin is reduced.
Solution Approach 2:
The system dynamically adjusts the charge sharing ratio by controlling the charge-sharing element based on operating conditions. When Vcc is low or target Vpp is high, the charge-sharing element is optimized to transfer more charge to the gate node, changing the voltage distribution parameters to maintain adequate gate voltage and reliable transistor operation.
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 proposed solution effectively increases the transfer efficiency of the voltage generating circuit by ensuring the voltage level at the gate node is sufficiently raised, improving the overall voltage generation efficiency, especially under low-voltage conditions, as demonstrated by a 20% improvement in transfer characteristics.
Implementation Method 1
The charge-sharing element is electrically connected to the final boosting node and a gate node of the transfer transistor, and is enabled during at least a part of a period the power supply voltage is stepped-up by the multi-boosting unit. The charge-sharing element also performs charge sharing between the final boosting node and the gate node of the transfer transistor.
Data Source
AI summary
A voltage generating circuit for a semiconductor memory device. The voltage generating circuit includes a multi-boosting unit for stepping up a power supply voltage, a transfer transistor connected to a final boosting node of the multi-boosting unit and an output node, and a charge-sharing element, electrically connected to the final boosting node and a gate node of the transfer transistor, enabled during at least a part of the period the power supply voltage is stepped-up by the multi-boosting unit and performing charge sharing between the final boosting node and the gate node of the transfer transistor.