一种特别适用于片上LDO系统的过流保护电路

An over-current protection circuit especially for capacitor-less LDO systems

依据电压比较器高低电平判决的基本原理,结合精确电流采样支路,设计了一种固定限流装置。此外,通过第二条电流采样支路,达到返送(foldback)功能,使得短路电流不到最大负载电流的10%,有效降低了LDO(LowDrop-out)系统的过流关断功耗。基于CZ6H 0.35μm标准CMOS工艺,应用Cadence工具进行仿真,结果显示,该过流保护电路可以把稳压器的最大输出电流限定在300mA,输出短路电流不到20mA,在无片外电容的条件下,系统表现出良好的瞬态响应效果;此外,该过流保护模块非常易于调节来适应于不同的标准输出电压。

With the basic principle of voltage comparator＇s judgment for high or low voltage level of combined with accurate current-sampled branch, a constant-current device is designed. Furthermore, the function of foldback is achieved by the second current-sampled branch, the short-circuit current is below to the 10% of maximum load current, which effectively reduces the over-current shut-down power dissipation of LDO systems. Based on CZ6H 0.35/am standard CMOS technology, simulated by the use of Cadence tool, the result reveals that the over-current protection circuit can limit the maximum at 300mA and the short-circuit current is below to 20mA.Under the capacitor-free condition, the LDO system shows favorable transient response. Otherwise, the overcurrent protection module is extremely easy to adjust to be adapted to variable standard output voltage.