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介绍了一种带频率抖动功能的振荡器,该振荡器结构简单、频率抖动效果明显,通过周期性改变振荡器内部比较器的比较阈值达到频率抖动的效果,可有效降低芯片电磁干扰。使用0.5μm BCD工艺对电路进行仿真,在25℃,TT工艺角下,振荡器中心频率为66.87kHz,频率抖动差值为±5.02kHz,频率抖动重复频率约为1.046kHz。电路适用于对电磁兼容性要求较高的开关电源芯片,具有很强的工程实用性。
An oscillator with frequency dithering function is introduced. The oscillator has a simple structure and obvious effect of frequency dithering. The effect of frequency dithering is achieved by periodically changing the comparison threshold of the internal comparator of the oscillator to effectively reduce the electromagnetic interference of the chip. The circuit simulation was carried out using a 0.5μm BCD process. At 25 ° C and TT process angle, the oscillator center frequency was 66.87kHz, the frequency jitter difference was ± 5.02kHz and the frequency jitter repetition frequency was about 1.046kHz. The circuit is suitable for the switching power supply chip with high electromagnetic compatibility requirements and has strong engineering practicability.