Multi-Stage Charge Pump for Low Voltage Applications
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Solution Overview
Problem
Conventional charge pumps face limitations in providing high voltage outputs at low supply voltages due to limited gain, high threshold voltage drops, and increased leakage, making them unsuitable for low voltage applications like EEPROMs, where high voltage is required for programming memory cells.
Innovation Solution
A charge pump system with multiple stages, utilizing PMOS devices and auxiliary capacitors to alternately charge and discharge, reducing threshold voltage effects and parasitic capacitance, allowing for higher voltage gain and output current even at low supply voltages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional capacitor-diode pairs are cascaded to increase voltage gain, then higher output voltage is achieved, but the threshold voltage drop increases dramatically limiting the number of cascadable pairs
Solution Approach 1:
The charge pump is divided into multiple independent stages, each with its own pumping capacitor and control logic. This segmentation allows each stage to operate independently with controlled voltage drops, preventing the cumulative threshold voltage accumulation that occurs in cascaded capacitor-diode pairs.
Solution Approach 2:
The invention changes the operating parameters by using thick oxide high voltage transistors instead of standard thin oxide devices. This parameter change allows the transistors to sustain larger voltage drops between gate and bulk without breakdown, enabling higher voltage gain while maintaining device reliability.
2Strength
If thick oxide high voltage transistors are used to sustain large voltage drops, then voltage gain is improved, but device area and complexity increase
Solution Approach 1:
Thick oxide high voltage transistors are used only in specific locations where large voltage drops must be sustained (in the pumping path), while standard thin oxide low voltage devices are used in other areas. This localized application of different device qualities optimizes the balance between voltage sustain capability and device area.
3Use of energy by moving object
If conventional charge pump operates at low supply voltage, then power consumption is reduced, but output current decreases due to limited charge transfer rate
Solution Approach 1:
Multiple pumping capacitors operate in an alternating sequence, with each capacitor charging while others discharge. This continuous operation ensures that charge transfer to the output is ongoing without interruption, maintaining high output current even at low supply voltages where each individual charge transfer event moves less charge.
4Strength
If conventional charge pump provides high voltage output, then voltage gain is improved, but leakage current increases due to breakdown effects
Solution Approach 1:
The invention changes the device parameter by using thick oxide transistors that can sustain higher voltage drops without entering breakdown. This parameter change allows the charge pump to provide high voltage output while keeping the transistors operating below their breakdown voltage, thereby minimizing leakage current.
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 system effectively provides a higher voltage output with sufficient current at low supply voltages, overcoming limitations of conventional charge pumps by optimizing gain and reducing leakage, making it suitable for very low voltage applications.
Implementation Method 1
at least one pumping capacitor coupled with the at least first pumping node
Data Source
AI summary
A method and system for providing an output voltage greater than a voltage provided by a voltage supply in a semiconductor device are disclosed. The method and system include providing a plurality of clock signals, providing a first stage and providing a second stage. The first stage includes at least a first pumping node, a pumping capacitor and a device coupled with the pumping node, and an auxiliary capacitor pair for providing an undershoot for the device for value(s) of the clock. The auxiliary and pumping capacitors receive a first portion of the clock signals. The second stage includes at least a second pumping node. The first and second portions of the clock signals are provided to the first and second stages, respectively. The first stage and the second stage are configured to alternately charge and fully discharge based on the clock signals.