一種低溫漂高電源抑制能力的振蕩器設計

摘" 要： 為了提升開關電源芯片中振蕩器的溫度特性和電源抑制能力，提出一種改進型拓撲結構的RC振蕩器。該振蕩器由電容充放電模塊、偏置電流源模塊、比較器模塊以及寄存器模塊組成。通過將電容的上下極板都接入電流源，并對電容下極板流過的電流進行采樣，引入負反饋對充放電電流源進行動態調節，從而減小電容上極板電壓通過溝道調制效應對充放電電流源的影響，增強充放電電流源的電源抑制能力。再配合偏置電流源模塊中經過溫度補償的偏置電流，得到具有低溫漂特性及高電源抑制能力的振蕩頻率?；贑SMC 0.18 μm BCD工藝完成了電路設計，仿真實驗結果表明，所設計的振蕩器工作頻率為411 kHz，電源電壓為2.6～3.8 V時頻率變化為0.119%，溫度為-40～125 ℃時頻率變化為3%。該振蕩器具有較強的電源抑制能力，能很好地滿足開關電源芯片中振蕩器的設計要求。

關鍵詞： RC振蕩器； 高電源抑制能力； 低溫漂； 電容充放電模塊； 振蕩頻率； 負反饋

中圖分類號： TN433?34" " " " " " " " " " " " " " "文獻標識碼： A" " " " " " " " " " " 文章編號： 1004?373X（2024）12?0108?07

Design of oscillator with low?temperature drift and high power supply rejection ability

WEN Lichang， ZHANG Ying， SHEN Junjie， XIONG Tianyu

（School of Integrated Circuit Science and Engineering （Industry?Education Integration School）， Nanjing University of Posts and

Telecommunications， Nanjing 210000， China）

Abstract： In order to improve the temperature characteristics and power supply rejection ability of the oscillator in switching power supply chip， a RC oscillator with improved topology structure is proposed. The oscillator is composed of capacitor charge?discharge module， bias current source module， comparator module and register module. The upper and lower plates of the capacitor are connected to the current source， the current flowing through the lower plate of the capacitor is sampled and introduced to the negative feedback， and the charging and discharging current source is adjusted dynamically， thereby reducing the influence of channel modulation effect on the charging and discharging current source by the voltage of the upper plate of the capacitor， and enhancing the power suppression ability of the charging and discharging current source. The oscillation frequency with low temperature drift characteristic and high power suppression ability is obtained by combining with the temperature?compensated current in the bias current source module. The circuit is designed based on CSMC 0.18 μm BCD process. The simulation results show that the operating frequency of the designed oscillator is 411 kHz， the frequency change is 0.119%， when the supply voltage is 2.6～3.8 V， and the frequency change is 3% when the temperature is -40～125 ℃. This oscillator has strong power suppression capability， and can well meet the design requirements of oscillators in switching power supply chips.

Keywords： RC oscillator; high power supply rejection ability; low?temperature drift; capacitor charging and discharging module; oscillation frequency; negative feedback

0" 引" 言

隨著工業和汽車電子領域對電源芯片需求的增長，開關電源芯片需要面對供電電壓波動大、環境溫度變化范圍廣等更嚴苛的工作條件，這對開關電源芯片中振蕩器性能提出了更高的要求。

振蕩器需要在溫度和電源電壓變化時，具有低溫漂性能和高電源抑制能力。現有的環形振蕩器在亞閾值區域工作時，表現出超低功耗的優異特性[1]，但其振蕩頻率的精度和溫漂易受偏置電流影響。……