一种频率与温度无关的片内 RC 振荡器设计

文章基于 SMIC 0.18 μm 互补金属氧化物半导体 (complementary metal oxide semiconductor, CMOS) 工艺, 设计了一种频率与温度无关的片内电流模 RC 振荡器, 该振荡器采用 1.8 V 电源供电, 输出频率为 100 MHz, 振荡器主要由温度补偿电流源、开关电容充放电回路、反相器比较延时单元以及时钟输出单元组成。通过 Cadence Spectre 仿真验证表明: 在 $ -40 \sim 125^{\circ}C $ 范围内, TT 工艺角条件下, 振荡器的输出频率范围为 $ 100.06 \sim 100.16 MHz $, 频率随温度变化为 0.10%, 用温度系数表示为 $ 6.06 \times 10^{-6} ^{\circ}C^{-1} $; SS 工艺角条件下, 振荡器的输出频率范围为 $ 99.90 \sim 100.23 MHz $, 频率随温度变化为 0.33%, 用温度系数表示为 $ 20.00 \times 10^{-6} ^{\circ}C^{-1} $; FF 工艺角条件下, 振荡器的输出频率范围为 $ 99.96 \sim 100.07 MHz $, 频率随温度变化为 0.11%, 用温度系数表示为 $ 6.67 \times 10^{-6} ^{\circ}C^{-1} $。

Based on the SMIC 0.18 $ \mu $m complementary metal oxide semiconductor (CMOS) process, this paper designs an on-chip current-mode RC oscillator whose frequency is independent of temperature. The oscillator adopts a 1.8 V power supply and the output frequency is 100 MHz. The oscillator is mainly composed of a temperature-compensated current reference, a switched capacitor charging and discharging circuit, an inverter comparison delay unit and a clock output unit. The simulation verification by Cadence Spectre shows that in the range of $ -40\ ^{\circ}C $ to $ 125\ ^{\circ}C $, the output frequency range of the oscillator is 100.06-100.16 MHz under the condition of TT process angle, and the frequency changes with temperature by 0.10%, expressed as $ 6.06\times10^{-6}\ ^{\circ}C^{-1} $ by the temperature coefficient; under the condition of SS process angle, the output frequency of the oscillator is in the range of 99.90-100.23 MHz, and the frequency changes with temperature by 0.33%, expressed as $ 20.00\times10^{-6}\ ^{\circ}C^{-1} $ by the temperature coefficient; under the condition of FF process angle, the output frequency of the oscillator is in the range of 99.96-100.07 MHz, and the frequency changes with temperature by 0.11%, expressed as $ 6.67\times10^{-6}\ ^{\circ}C^{-1} $ by the temperature coefficient.