Charge Pump Circuit Voltage Shifting for Noise Reduction
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Solution Overview
Problem
Charge pumps in various applications face issues with unwanted spurious noise due to large transients across parasitic device capacitances, which can offset the effectively transferred charge, and switching voltage drifts that misalign control signals with transistor switching voltages.
Innovation Solution
The charge pump circuit includes a voltage shifting circuit that biases control signals relative to switching threshold parameters, ensuring accurate alignment and compensation for voltage drifts, and a control circuit that generates control signals based on command voltages, with a second voltage supply less than the main supply to manage power efficiently.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If full swing digital signals are used to control current source switches, then switching speed is improved, but large transients are induced across parasitic device capacitances causing spurious noise
Solution Approach 1:
A voltage shifting circuit is introduced as an intermediary between the digital control signal source and the charge pump switching transistors. This circuit shifts the voltage levels of the digital control signals to match the switching voltages of the transistors, enabling clean switching without large transients across parasitic capacitances, thus eliminating spurious noise while maintaining fast switching performance
2Device complexity
If control signals are generated without voltage shifting, then device complexity is reduced, but switching voltage drifts cause misalignment between control signals and transistor switching voltages
Solution Approach 1:
The voltage shifting circuit is designed to automatically track and compensate for switching voltage drifts in the charge pump transistors. By monitoring the actual switching voltages and dynamically adjusting the control signal voltage levels, the circuit maintains accurate alignment between control signals and transistor switching points, ensuring reliable operation without requiring complex external calibration circuits
Data Source
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AI summary
A charge pump circuit is disclosed. The charge pump circuit includes a first circuit powered by a first supply voltage and configured to adjust a voltage of an output in response to first and second sets of control signals. The first circuit includes a set of transistors having respective switching voltages. A control circuit powered by a second voltage, less than the first supply voltage, is configured to generate the first and second sets of control signals. A voltage shifting circuit is configured to bias voltages of the first and second sets of control signals relative to the switching voltages.