Multistage Charge-Pump Regulator Using Segmented Low-Voltage Transistors
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Solution Overview
Problem
The integration of high voltage PMOS structures is costly and impractical for regulating charge-pump generated boosted voltages in multilevel non-volatile flash memory devices, as existing fabrication processes are streamlined for low voltage CMOS structures, making it necessary to introduce additional processing steps and masks for high voltage transistors.
Innovation Solution
A multistage circuit is implemented with a first stage powered at the unboosted power supply voltage and an output stage supplied at the unregulated charge-pump generated boosted voltage, using a transistor of opposite conductivity type, coupled with a resistive pull-up or voltage limiter, allowing for regulation without high voltage transistor structures, and optionally incorporating an output follower stage for reduced current absorption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high voltage PMOS structures are integrated for regulating charge-pump generated boosted voltages, then voltage regulation capability is improved, but fabrication cost increases and manufacturing complexity increases
Solution Approach 1:
The voltage regulator is divided into two separate stages: a first stage powered by unboosted power supply voltage for control functions, and a second stage powered by the boosted voltage for voltage regulation. This segmentation allows each stage to use transistors optimized for its specific voltage level, eliminating the need for expensive high voltage PMOS structures in the entire regulator.
Solution Approach 2:
Instead of using the conventional approach where high voltage PMOS transistors are used throughout the regulator to handle the boosted voltage, the patent inverts the approach by using low voltage transistors in the first stage and only using high voltage capability where absolutely necessary (second stage), thereby reducing overall manufacturing complexity and cost.
2Reliability
If high voltage PMOS structures are integrated for regulating boosted voltages, then voltage regulation capability is improved, but device complexity increases
Solution Approach 1:
The regulator is segmented into two functional stages with different voltage requirements. The first stage handles control signals at low voltage, while the second stage handles the boosted voltage regulation. This segmentation simplifies the overall device complexity by allowing each stage to use transistors with appropriate voltage ratings rather than requiring all transistors to be high voltage types.
Solution Approach 2:
Different parts of the regulator are designed with different transistor types matched to their local voltage requirements. The first stage uses low voltage transistors suitable for control circuitry, while only the second stage uses transistors capable of withstanding the boosted voltage, optimizing both performance and simplicity.
3Reliability
If additional processing steps and masks are introduced for high voltage transistors, then voltage regulation at boosted levels is enabled, but manufacturing productivity decreases
Solution Approach 1:
By segmenting the regulator into two stages with different voltage requirements, the patent enables the majority of the circuit (first stage) to be manufactured using standard low voltage CMOS processes, thereby maintaining high manufacturing throughput while still achieving boosted voltage regulation capability in the second stage.
Solution Approach 2:
The patent uses inexpensive low voltage transistors for the first stage that can be manufactured with standard processes, rather than requiring expensive high voltage transistors throughout the entire circuit. This approach maintains productivity by using cost-effective, easily manufactured components for the majority of the regulator.
Data Source
AI summary
A multistage circuit for regulating the charge voltage or the discharge current of a capacitance of an integrated device at a certain charge-pump generated boosted voltage is implemented without integrating high voltage transistor structures having a type of conductivity corresponding to the same sign of the boosted voltage (high-side transistors). The multistage circuit current includes at least a first stage, and an output stage in cascade to the first stage and coupled to the capacitance. The first stage is supplied at an unboosted power supply voltage of the integrated device, and the output stage is supplied at an unregulated charge-pump generated boosted voltage. The first stage includes a transistor having a type of conductivity corresponding to an opposite sign of the boosted voltage and of the power supply voltage. The drain of the output stage transistor is coupled to the boosted voltage either through a resistive pull-up or a voltage limiter.