Spread spectrum clock generation (SSCG) is an important technique for electromagnetic interference reduction. To achieve the goal of lowering peak power, clock signal is intentionally “jittered.” In circuit implementation, there are mainly three ways to carry out the task of jittering the clock: voltage-controlled oscillator modulation, phase-locked loop divider dithering, and clock-period direct manipulation. From the perspective of spread result, there are three types including down spread, central spread, and up spread. Being an effective solution for lowering the harmful electromagnetic peak power, SSCG is also faced with a challenge of preserving the integrity of the clock signal. In this paper, a novel approach of always-on boundary spread is presented. It is based on time-average-frequency concept. Its aim is to maximize frequency modulation depth while precisely controls clock's impact on system operation. Theoretical analysis is performed, experimental validation is provided through an implementation on field programmable gate array (FPGA). Furthermore, a commercial product is used to demonstrate the feature of “always on” enabled by this SSCG technology.

中文翻译：

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一种新颖的扩频时钟生成技术：始终在线的边界扩展 SSCG

扩频时钟生成 (SSCG) 是减少电磁干扰的一项重要技术。为了达到降低峰值功率的目的，时钟信号被故意“抖动”。在电路实现中，主要有三种方式来完成时钟抖动任务：压控振荡器调制、锁相环分频器抖动和时钟周期直接操纵。从点差结果来看，分为向下点差、中央点差和向上点差三种。作为降低有害电磁峰值功率的有效解决方案，SSCG 也面临着保持时钟信号完整性的挑战。在本文中，提出了一种始终在线的边界传播的新方法。它基于时间-平均-频率概念。其目的是最大限度地提高频率调制深度，同时精确控制时钟对系统操作的影响。执行理论分析，通过现场可编程门阵列 (FPGA) 的实现提供实验验证。此外，还使用商业产品来演示该 SSCG 技术支持的“始终在线”功能。