Supply Voltage Circuit with Step-Down Unit for Thin-Film Capacitors
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Solution Overview
Problem
Conventional supply voltage generating circuits for semiconductor storage devices face challenges in reducing chip area due to the need for thick-film transistors to withstand varying external supply voltages, which increases the circuit area and current consumption, especially when using thin-film capacitors for boosting voltage.
Innovation Solution
A supply voltage generating circuit that includes a power-supply step-down unit to reduce external power supply voltage within the breakdown-voltage range of capacitor elements, allowing the use of thin-film capacitor elements for all capacitors, and a switch circuit to adjust the number of booster stages based on the applied power supply voltage, enabling efficient voltage stepping and reduced chip area.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If thick-film transistors are used to withstand varying external supply voltages, then the circuit can handle different voltage specifications, but the chip area increases
Solution Approach 1:
The patent applies dynamics by making the transistor film thickness selectable rather than fixed. The circuit can dynamically switch between thick-film and thin-film transistor configurations based on the external supply voltage conditions, allowing adaptability to different voltage specifications while minimizing chip area by using thinner films when possible
Solution Approach 2:
The patent changes the parameter of transistor oxide-film thickness based on operating conditions. By selecting different film thicknesses according to the external supply voltage, the circuit achieves voltage specification adaptability without consistently requiring large-area thick-film transistors
2Reliability
If thick-film transistors are used for voltage withstand capability, then the circuit reliability improves, but the current consumption increases due to gate leakage
Solution Approach 1:
The patent changes the oxide-film thickness parameter of transistors based on the external supply voltage conditions. By using thin-film transistors when the voltage is within acceptable ranges and only switching to thick-film transistors when necessary for voltage withstand capability, the circuit maintains reliability while minimizing gate leakage current and associated power consumption
3Area of stationary object
If thin-film capacitor elements are used for voltage boosting, then the chip area is reduced, but the circuit cannot handle external supply voltages exceeding the breakdown voltage
Solution Approach 1:
The patent applies dynamics by making the transistor film thickness selectable rather than fixed. The circuit can dynamically switch between thick-film and thin-film transistor configurations based on the external supply voltage conditions, allowing adaptability to different voltage specifications while minimizing chip area by using thinner films when possible
Solution Approach 2:
The patent introduces a voltage selection mechanism that acts as an intermediary between the external power supply and the booster circuit. This intermediary selects appropriate transistor film thickness based on the external voltage, protecting thin-film capacitors from overvoltage while enabling their area-efficient use
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
This configuration enables the use of thin-film capacitor elements for all capacitors, reducing chip area and maintaining stable output voltage, even when the external supply voltage exceeds the breakdown voltage of thin-film transistors, by stepping down high voltages and adjusting booster stages, thus optimizing chip layout and power efficiency.
Implementation Method 1
a power-supply step-down unit for stepping down voltage of an external power supply to a voltage within a breakdown-voltage range of the capacitor elements
Implementation Method 2
a booster that outputs a boosted voltage upon generating the boosted voltage by charge pumping of a capacitor element
Data Source
AI summary
A supply voltage generating circuit that enables a reduction in chip area includes: a booster for outputting a boosted voltage upon generating the boosted voltage by charge pumping of a capacitor element; a power-supply step-down unit for stepping down voltage of an external power supply to a voltage within a breakdown-voltage range of the capacitor element, and applying the stepped-down voltage to the power supply of the booster; and a switch element for switching between application of the external power supply to the power supply of the booster directly or via the power-supply step-down unit. The booster comprises multiple stages of booster circuits. The thicknesses of gate oxide films of capacitor elements constituted by MOS transistors included in respective ones of the booster circuits are the same and are made smaller than the thickness of a gate oxide film of a MOS transistor included in a load circuit having the output of the booster at its power supply.