Charge Pump Degeneration Circuit Reduces Flicker Noise
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Solution Overview
Problem
In wireless communications, radio frequency circuits face challenges in achieving low error vector magnitude (EVM) due to noise from phase-locked loops (PLL) and linearity issues in transceivers, with existing charge pumps not effectively reducing flicker noise and maintaining circuit reliability.
Innovation Solution
A high-speed and low-noise charge pump design incorporating a degeneration circuit, thin gate oxide transistors, and a switch circuit to reduce transconductance and operating voltage, thereby minimizing flicker noise and improving linearity, while ensuring reliable operation by operating in a low voltage area.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a charge pump uses a conventional charging current source transistor with high transconductance, then the charging current can be provided efficiently, but the flicker noise of the charging current source transistor increases
Solution Approach 1:
The patent introduces a degeneration circuit as an intermediary component between the power supply terminal and the charging current source transistor. This degeneration circuit includes a degeneration transistor that acts as a mediator to reduce the transconductance of the charging current source transistor, thereby reducing flicker noise while still providing the necessary charging current. The degeneration circuit serves as a buffer that mediates between the need for efficient current provision and the need to minimize noise.
2Reliability
If a charge pump uses a thick gate oxide transistor to operate in high voltage area, then the circuit reliability is ensured, but the switching response speed and charge-discharge speed are slower
Solution Approach 1:
The patent changes the voltage parameter by introducing a degeneration circuit that reduces the operating voltage from the high voltage area (1.8V-2.5V) to a low voltage area (0.8V-0.9V). This parameter change enables the use of thin gate oxide transistors in the switch circuit, which have smaller parasitic capacitance and faster switching response speed, while the degeneration circuit ensures that the voltage reduction does not compromise circuit reliability.
3Speed
If a charge pump uses a thin gate oxide transistor to operate in low voltage area, then the switching response speed and charge-discharge speed are faster, but the circuit may be vulnerable to voltage stress
Solution Approach 1:
The degeneration circuit serves as a protective intermediary that prevents direct exposure of the thin gate oxide transistor to high voltage stress. By positioning the degeneration transistor between the power supply and the switch circuit, it mediates the voltage levels, allowing the thin gate oxide transistor to operate safely in the low voltage area while maintaining fast switching performance.
4Productivity
If a charge pump uses conventional transistors with high transconductance, then the current provision is efficient, but the linearity of the charge pump is poor
Solution Approach 1:
The patent changes the transconductance parameter by introducing the degeneration circuit, which reduces the transconductance of the charging current source transistor. This parameter change improves the linearity of the charge pump, as lower transconductance reduces the non-linear effects in the current provision, while the degeneration circuit ensures that the current provision efficiency is maintained through proper biasing and current mirroring.
Data Source
AI summary
One example charge pump is provided. The example charge pump includes a degeneration circuit, a charging current source transistor, a switch circuit and a discharging current source transistor. The charging current source transistor provides a charging current. The degeneration circuit is coupled between a first terminal of the charging current source transistor and a power supply terminal. The degeneration circuit degrades a first voltage corresponding to the power supply terminal to a second voltage. The switch circuit is coupled between a second terminal of the charging current source transistor and a load. The switch circuit controls a charging current output to the load.