Pulse Generator Mixing Dual Clocks for Charge Pump Control
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Solution Overview
Problem
Existing clock systems, such as charge pumps, face challenges in reducing charge transfer efficiently due to integer frequency division, which can result in excessive reduction of charge delivery, and phase-locked loops (PLLs) are complex and not always available or desired.
Innovation Solution
A pulse generator that mixes pulses of two clocks with different frequencies, using a multiplexer controlled by combinatorial logic to produce a pulse train with an effective frequency that is a non-integer division of the main clock frequency, allowing for fine-tuning of charge delivery in charge pumps.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If an integer frequency divider is used to reduce the frequency of the system clock, then the frequency reduction is achieved, but the charge transfer is reduced to a greater extent than desired
Solution Approach 1:
The patent applies dynamics by making the clock source selection variable and adjustable rather than fixed. The system dynamically switches between the first clock (higher frequency) and second clock (lower frequency) based on a control signal, enabling the charge pump to achieve non-integer frequency division ratios and optimize charge transfer while maintaining desired output frequency.
Solution Approach 2:
The patent changes the parameter of clock frequency by providing two different clock frequencies and selectively switching between them. This allows the system to achieve frequency division ratios that are not limited to integers, thereby preventing excessive charge transfer reduction while still achieving the desired frequency reduction.
2Measurement precision
If a phase-locked loop is used to generate a clock with a fractional frequency, then fine frequency control is achieved, but the device complexity and surface area increase
Solution Approach 1:
The patent segments the clock generation function by separating the frequency division task from the charge pump control. Instead of using a complex PLL to generate a single fractional frequency clock, the system uses two simple integer-divided clocks and selectively switches between them, reducing circuit complexity while achieving effective fractional frequency control.
Solution Approach 2:
The patent introduces a multiplexer as an intermediary component that selects between two clock sources based on a control signal. This intermediary enables fractional frequency division without requiring a complex PLL, as the multiplexer simply switches between pre-generated clock frequencies based on the desired division ratio.
3Speed
If the frequency of the system clock is reduced by a factor of two, then the charge pump operates at lower frequency, but the charge delivery is reduced more than desired
Solution Approach 1:
The system dynamically adjusts the clock frequency by switching between two sources, allowing the charge pump to operate at effectively non-integer divided frequencies. This dynamic adjustment enables optimization of charge delivery while maintaining appropriate operating frequency, avoiding the excessive charge reduction that occurs with fixed integer division.
Solution Approach 2:
The clock selection mechanism provides multi-functionality by serving both frequency control and charge transfer optimization. The same switching mechanism that controls frequency also optimizes charge delivery by selecting the appropriate clock source based on the desired operating point, eliminating the need for separate control circuits.
Data Source
AI summary
The present disclosure provides a pulse generator which generates a pulse train by mixing pulses of a first clock having a first frequency, with pulses of a second clock having a second frequency. Over a predefined time period, the combination of pulses results in a pulse train having an effective frequency which is between the first and second frequencies. A multiplexer is used to select which of the first and second clocks should be provided to the output. Depending on the desired target frequency, the multiplexer is controlled to mix differing amounts of pulses from the first and second clocks. A multiplexer is controlled by a control signal, which is generated using combinatorial logic using the first clock as an input. The pulse generator may be used, for example, as a clock for a charge pump.