Capacitor-Swapping Charge Pump for Wide-Range Low-Noise Control
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Solution Overview
Problem
Conventional charge pump circuits face a trade-off between noise performance and operation range, particularly in low-voltage applications, where the narrow operating range of the control voltage limits their effectiveness.
Innovation Solution
The proposed charge pump circuit employs a capacitor swapping technique, utilizing controllable current generating circuits and an interconnection circuit to alternate between charging and discharging modes, allowing for a wider operation range while maintaining good noise performance by using PMOS and NMOS transistors to manage current sources.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the overdrive voltage V OV is increased to reduce noise from current sources, then noise performance is improved, but the operating range of the control voltage becomes even narrower
Solution Approach 1:
The charge pump circuit is segmented into two independent pumping circuits (first and second pumping circuits) that operate alternately. Each circuit has its own current sources and capacitors, allowing them to be optimized independently. This segmentation enables each current source to operate with high overdrive voltage for low noise while the control voltage can sweep through a wider range by switching between the two circuits.
Solution Approach 2:
The two pumping circuits operate in periodic alternation, with each circuit active for half of the control voltage cycle. The first pumping circuit operates when the control voltage is in the first half-cycle, and the second pumping circuit operates when the control voltage is in the second half-cycle. This periodic action allows each current source to maintain optimal operating conditions while the overall system achieves a wide control voltage range.
2Reliability
If the conventional charge pump circuit is used with narrow operating range to ensure MOS transistors operate in saturation mode, then current source performance is maintained, but the circuit becomes unsuitable for low-voltage applications
Solution Approach 1:
The circuit is divided into two pumping circuits with separate current sources and capacitors. Each current source can be independently designed to maintain saturation mode operation with appropriate overdrive voltage, while the alternating operation allows the control voltage to extend beyond the narrow range required for single-circuit saturation operation.
Solution Approach 2:
The circuit parameters are dynamically changed by switching between two configurations. During the first half-cycle, the first pumping circuit parameters are active; during the second half-cycle, the second pumping circuit parameters are active. This parameter switching enables the system to maintain optimal transistor operation while adapting to a wider voltage range suitable for low-voltage applications.
3Reliability
If the control voltage is limited to a narrow range (V1-V OV to V2+V OV) to ensure proper MOS transistor operation, then current source reliability is maintained, but the charge pump circuit cannot function effectively in low-voltage environments
Solution Approach 1:
The charge pump circuit employs periodic action by alternating between two pumping circuits. Each current source operates during its designated half-cycle with controlled voltage limits that ensure saturation mode operation. The periodic switching allows the system to maintain reliable current source operation while achieving effective low-voltage operation through the alternating configuration.
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 design breaks the trade-off between operation range and noise performance, enabling a wider control voltage range with reduced noise, particularly in low-voltage applications, and improves the frequency locking capability of PLL circuits.
Implementation Method 1
A current source of the pull-up circuit and a current source of a pull-down circuit may be implemented by metal-oxide-semiconductor field-effect transistors (MOS transistors). Ideally, the MOS transistors are biased to operate in a saturation mode.
Implementation Method 2
a first capacitor, having a first plate and a second plate; a second capacitor, having a first plate and a second plate
Data Source
Figure 1
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Figure 3
AI summary
A charge pump circuit includes first and second capacitors, first and second controllable current generating circuits, and an interconnection circuit. A first terminal of the first controllable current generating circuit is coupled to a first plate of the first capacitor. A first terminal of the second controllable current generating circuit is coupled to a first plate of the second capacitor. During a first operation mode, the first controllable current generating circuit refers to a first control input for selectively providing a first current, and the second controllable current generating circuit refers to a second control input for selectively providing a second current. During a second operation mode, the interconnection circuit couples the first plate of the second capacitor to a first power rail, and couples both of the second plate of the second capacitor and the first plate of the first capacitor to an output terminal.