CMOS Charge Pump Circuit Voltage Jump Suppression
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Solution Overview
Problem
Traditional CMOS charge pump circuits experience significant voltage jumps when logic signals switch, affecting circuit stability and output voltage stability during horizontal readout in CMOS image sensors.
Innovation Solution
The addition of two current mirrors and two operational amplifiers in the CMOS charge pump circuit, which generate mirror currents to stabilize the output voltage by suppressing feed-through currents and ensuring consistent current flow through steering switches.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If traditional CMOS charge pump circuit switches logic signals, then charge pump operation is controlled, but significant voltage jumps occur affecting circuit stability
Solution Approach 1:
The operational amplifiers are configured to preemptively counteract voltage changes before they manifest as instability. The feedback loops detect early signs of voltage deviation and adjust the output accordingly, preventing the full voltage jump from occurring. This preliminary corrective action maintains stability while allowing normal switching operation.
Solution Approach 2:
The circuit incorporates feedback mechanisms where operational amplifiers continuously monitor the output voltage and adjust the charge pump operation to maintain stability. The feedback loop detects voltage deviations caused by switching and generates corrective signals that counteract these changes, ensuring the output remains stable despite logic signal transitions.
2Productivity
If switches M1-M4 are used for voltage control, then charge pump switching is achieved, but large voltage jumps are generated
Solution Approach 1:
Operational amplifiers are introduced as intermediary elements between the switching transistors and the output. These amplifiers act as buffer stages that smooth out the abrupt voltage changes caused by direct switching. The intermediaries translate the digital switching signals into analog control signals that drive the charge pump more smoothly, reducing voltage jumps while maintaining switching functionality.
3Power
If charge pump generates high voltage for pixel units, then driving capability is improved, but circuit stability is affected by switching
Solution Approach 1:
The operational amplifiers create feedback loops that continuously monitor the high voltage output and adjust the charge pump operation to maintain stability. When switching causes voltage deviations, the feedback mechanism detects these changes and generates corrective control signals, ensuring the high voltage output remains stable and reliable for driving pixel units despite the inherent switching disturbances.
Data Source
AI summary
The present invention discloses a device of CMOS image sensor, exactly, relates to a kind of CMOS charge pump circuit. The invention compromises: two current mirrors and two operational amplifiers are added into the CMOS charge pump circuit. The feed-through current is suppressed when signal switches in the said circuit. It solved the problem of the big voltage jump of the output voltage when the logic signal switches. It guarantees the stabilities of the circuit and the output voltage.