Charge Pump Circuit Using PMOS Transistors for Low Voltage Operation
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Solution Overview
Problem
Existing charge pump circuits face efficiency issues due to increased threshold voltage of NMOS transistors and insufficient turn-on of PMOS transistors at low input voltages, leading to reduced voltage boosting efficiency and potential circuit failure.
Innovation Solution
A charge pump circuit design incorporating a switch unit with a first NMOS transistor and at least two in-series coupled PMOS transistors, along with transmission and charging units, ensures each MOS transistor has a turn-on voltage of two times the input voltage, addressing the threshold voltage issues and ensuring normal operation even at low input voltages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If NMOS transistors are used in the charge pump circuit, then the circuit can be implemented with standard process, but the threshold voltage increases leading to insufficient turn-on and reduced transmission efficiency
Solution Approach 1:
The patent changes the type of transistor used in the charge pump circuit from NMOS to PMOS. This parameter change exploits the different threshold voltage characteristics of PMOS transistors, which have lower threshold voltages and can be fully turned on even at low input voltages, thereby resolving the issue of insufficient turn-on and reduced transmission efficiency associated with NMOS transistors
2Productivity
If the input voltage VDD is reduced to meet scaling requirements, then chip integration level improves, but the ability to fully turn on PMOS transistors is compromised
Solution Approach 1:
The patent changes the transistor type parameter from NMOS to PMOS, which fundamentally alters the voltage requirements for proper operation. PMOS transistors can be fully turned on at lower voltages compared to NMOS transistors, allowing the charge pump to maintain reliable transistor operation even as the input voltage VDD is reduced to meet chip scaling and integration requirements
3Strength
If multiple NMOS transistors are cascaded to achieve higher voltage multiplication, then the output voltage increases, but the cumulative threshold voltage loss prevents proper turn-on of later stage transistors
Solution Approach 1:
The patent changes the transistor type parameter throughout the cascaded stages from NMOS to PMOS. This enables each stage to contribute its full voltage multiplication capability without suffering from cumulative threshold voltage losses, as PMOS transistors maintain sufficient turn-on capability even in later stages of the voltage multiplication chain
Data Source
AI summary
A charge pump circuit includes a switch unit adapted to transmit charges from the input of the charge pump to the output of the charge pump; a transmission unit adapted to control turn-on or cut-off of an MOS transistor in the switch unit; and a charging unit in one-to-one correspondence with a PMOS transistor in the switch unit and adapted to store charges to boost the transmission voltage. A first NMOS transistor and at least two PMOS transistor are used as the switch unit during transmission of the charges, so that normal work can be enabled with high transmission efficiency in the case of a low source voltage.