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为了防止芯片过热,提高芯片可靠性和稳定性,采用0.5μm CMOS工艺,设计了一种具有迟滞比较器的过热保护电路。由于采用了折叠式运放,使得比较器输入范围更大,灵敏度和迟滞性能更好。利用Cadence Spectre仿真工具对电路进行了仿真,结果表明电源电压为4.5～7 V时,过温保护阈值变化量极小,表现出输出信号对电源的良好抑制。当温度超过130℃时,输出信号翻转,芯片停止工作;温度降低至90℃时,芯片恢复工作。此电路可以通过调整特定管子的尺寸而控制两个阈值电压的大小,从而避免热振荡的发生。
In order to prevent the overheating of the chip and improve the reliability and stability of the chip, a 0.5μm CMOS process is adopted to design an overheat protection circuit with a hysteresis comparator. As a result of folding op amp, making the comparator input range greater sensitivity and hysteresis performance better. The circuit was simulated with Cadence Specter simulation tool. The results show that the variation of over-temperature protection threshold is very small when the power supply voltage is 4.5-7V, which shows that the output signal can restrain the power supply well. When the temperature exceeds 130 ℃, the output signal flip, the chip stops working; the temperature dropped to 90 ℃, the chip resumes work. This circuit can be controlled by adjusting the size of a particular tube two threshold voltage size, thus avoiding the occurrence of thermal oscillations.