Charge Pump Merging for PLL Area Reduction

Solution Overview

Problem

Phase-locked loops (PLLs) and clock and data recovery (CDR) circuits require two charge pumps to achieve a capacitance multiplier effect, leading to increased chip area and manufacturing costs due to the need for two charge pumps.

Innovation Solution

A charge pump sharing technique is implemented using a current source circuit, a current sink circuit, and a switch circuit, which generates two currents from a single current source and sink, reducing the need for multiple charge pumps and minimizing chip area.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If two charge pumps are used to provide different currents to the active filter, then the PLL can achieve the capacitance multiplier effect, but the chip area and manufacturing costs increase

Engineering Contradiction:

Improvecapacitance multiplier effectVSAvoidchip area

Core Design Contradiction:

ReliabilityVSArea of stationary object

Solution Approach 1:

The patent combines two separate charge pumps into a single charge pump that generates both first and second currents. The switch circuit selectively connects the current source to different output terminals based on control signals, allowing one charge pump to perform the function previously requiring two charge pumps, thereby reducing chip area while maintaining the capacitance multiplier effect

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The single charge pump is designed with multi-functionality to provide both first current and second current to the active filter. By incorporating a switch circuit that can route the current to different terminals based on control signals, the charge pump achieves universal functionality that replaces two dedicated charge pumps, reducing overall system complexity and chip area

Inventive Principle:

Principle #6Universality (Multi-functionality)

2Reliability

If two charge pumps are used to provide different currents to the active filter, then the PLL can achieve the capacitance multiplier effect, but the manufacturing costs increase

Engineering Contradiction:

Improvecapacitance multiplier effectVSAvoidmanufacturing costs

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The patent combines two separate charge pumps into a single charge pump that generates both first and second currents. The switch circuit selectively connects the current source to different output terminals based on control signals, allowing one charge pump to perform the function previously requiring two charge pumps, thereby reducing chip area while maintaining the capacitance multiplier effect

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The single charge pump is designed with multi-functionality to provide both first current and second current to the active filter. By incorporating a switch circuit that can route the current to different terminals based on control signals, the charge pump achieves universal functionality that replaces two dedicated charge pumps, reducing overall system complexity and chip area

Inventive Principle:

Principle #6Universality (Multi-functionality)

Data Source

PatentUS9831766B2Charge pump and associated phase-locked loop and clock and data recovery

Publication Date: 2017.11.28 MEDIATEK INC

AI summary

A charge pump includes a current source circuit, a current sink circuit and a switch circuit. The switch circuit is coupled between the current source circuit and the current sink circuit, and is arranged for generating a first current at a first output terminal and generating a second current at a second output terminal according to a first control signal and a second control signal, wherein each of the first current and the second current is generated from the current source circuit.