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设计了一种具有扩频模式、适用于DC-DC开关变换器的片内RC振荡器.采用外部滤波修调电路来调整充放电电流,对振荡信号的频率起调节和稳定的作用.采用随机码扩频技术以减小脉冲宽度调制过程中产生的电磁干扰峰值,降低开关电源的电磁干扰.该RC振荡器基于0.5 μm BCD工艺进行设计.仿真结果表明,该RC振荡器可以对振荡时钟进行修正,有效降低了电磁干扰.该RC振荡器在非扩频模式时,可以通过外部电路来调整振荡频率偏差,振荡频率为18 MHz,占空比为50％,功率谱峰值为-0.05 dBm.与非扩频模式相比,该RC振荡器在扩频工作模式下的振荡信号功率谱峰值降低了19.95 dBm.“,”An on-chip RCoscillator with spread spectrum mode was designed for the PWM switching mode DC-DC converter.An external filter circuit was used to trim the output frequency of the oscillation signal by changing the charge-discharge current.The spread spectrum technology which employed random code was used to reduce the electromagnetic interference from the switching power supply that occurred in the processing of pulse width modulation.The circuit was designed in a 0.5 μm BCD process.The simulation results showed that the proposed oscillator could trim the frequency of the oscillation signal properly and reduce the electromagnetic interference effectively.In normal fix frequency mode,the oscillating frequency offset could be trimmed by the external circuit.The frequency of oscillation signal was 18 MHz with 50％ duty cycle,and the maximum power spectral density was -0.05 dBm.Beyond that,the maximum power spectral density was reduced by 19.95 dBm while it worked in the spread spectrum mode.