Charge Pump Leakage Compensation via Feedback Current Sensor
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Solution Overview
Problem
Charge leakage in the capacitive load of charge pump circuits introduces errors in phase detection, leading to clock jitter in phase lock loops, particularly in deep submicron CMOS integrated circuits.
Innovation Solution
A charge pump apparatus with a current sensor and feedback network that injects a compensation current into the capacitive load to counteract leakage, ensuring the mean net current at the output node is zero, thereby stabilizing the output voltage and reducing clock jitter.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If deep submicron CMOS devices are used to achieve high-speed operation, then operating speed is improved, but charge leakage increases causing clock jitter
Solution Approach 1:
The patent implements a feedback mechanism where a current sensor continuously monitors the charge leakage current at the capacitive load, and a feedback network adjusts the compensation current accordingly. The feedback loop compares the actual leakage current with the desired compensation level and dynamically adjusts the compensation current to maintain zero net current at the output node, thereby eliminating clock jitter while preserving high-speed operation.
Solution Approach 2:
The patent introduces an intermediary compensation current path that acts as a mediator between the charge pump output and the capacitive load. This compensation current, generated through a controlled current source and adjusted by the feedback network, serves as an intermediate element that counteracts the harmful leakage current before it can affect the output voltage, thus resolving the contradiction between high-speed operation and charge leakage.
2Ease of operation
If a capacitive load is used in the charge pump, then filtering and voltage conversion are achieved, but charge leakage occurs causing phase detection errors
Solution Approach 1:
The feedback network continuously monitors the current through the capacitive load using a current sensor and dynamically adjusts the compensation current to counteract leakage. This feedback mechanism ensures that the capacitive load maintains its filtering function while the compensation current eliminates the charge leakage that would otherwise cause phase detection errors, thereby preserving both filtering capability and measurement precision.
Solution Approach 2:
The patent extracts the harmful charge leakage component from the overall current at the capacitive load by introducing a separate compensation current path. The current sensor specifically detects the leakage current, and the feedback network generates a compensation current that is injected into the output node to counteract only the leakage portion, leaving the useful filtering function of the capacitive load intact while eliminating its harmful effects on phase detection accuracy.
3Reliability
If compensation current is injected to counteract leakage, then charge leakage is reduced, but device complexity increases
Solution Approach 1:
The feedback network is designed to provide automatic compensation without requiring complex external control circuits. The current sensor and feedback network work together to automatically adjust the compensation current based on real-time leakage conditions, eliminating the need for manual calibration or complex control logic. This self-adjusting feedback mechanism achieves effective charge leakage compensation while keeping the added circuit complexity minimal and integrated.
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
Effectively alleviates the detrimental effects of charge leakage by maintaining a stable output voltage, reducing clock jitter and ensuring accurate phase/frequency control of the output clock.
Implementation Method 1
a current sensor coupled between the internal node and the output node to sense the current
Implementation Method 2
a feedback network to generate the bias voltage in accordance with an output of the current sensor
Implementation Method 3
a capacitive load coupled to the output node; ensuring the mean net current at the output node is zero
Data Source
AI summary
An apparatus comprises a charge pump to receive a phase signal representing a result of a phase detection and to output a current flowing between an internal node of the charge pump and an output node of the charge pump; a capacitive load coupled to the output node; a current source controlled by a bias voltage to output a compensation current to the output node; a current sensor coupled between the internal node and the output node to sense the current; and a feedback network to generate the bias voltage in accordance with an output of the current sensor. A comparable method is also disclosed.