一种可编程USB限流开关设计

Design of a Programmable USB Current Limiting Switch

为避免USB系统中热插拔产生的瞬间浪涌电流对设备造成的损伤,提出一种可编程USB限流开关电路。电路采用NEC 0.35μm BCD工艺进行设计,并分析该限流开关的结构原理和关键电路。本电路工作电压为2.7V至5.5V,可编程限流范围为100mA至500mA,导通电阻典型值为70mΩ。为了提高系统可靠性,芯片内部配有过温保护、欠压保护以及短路保护功能,当USB系统出现浪涌电流时,本电路可立即传送错误指示信号至微控制器,关闭系统,提高电路系统的稳定性。流片后测试证明了该USB限流开关的可靠性;其电流检测精度可达到10%,发生短路时响应速度可达到2μs,达到了预期的性能指标。

A programmable USB current limiting switch circuit is proposed in order to avoid thedamage to equipment caused by instantaneous surge current generated by hot plugging in USB system.The circuit is designed by NEC 0.35 滋m BCD process, and the structure principle and key circuit of thecurrent limiting switch are analyzed. The operating voltage of this circuit is 2.7V耀5.5V, the programmablecurrent limit range is 100mA耀500mA, and the on-resistance is typically 70m赘. In order to improve thereliability of the system, the chip is equipped with over-temperature protection, under-voltage protectionand short-circuit protection functions. When a surge current occurs in the USB system, this circuit canimmediately send an error indication signal to the microcontroller to shut down the system and improvethe stability of the circuit system. The reliability of the USB current limiting switch was proved by thepost-chip test. The current detection accuracy can reach 10%, and the response speed can reach 2滋swhen a short circuit occurs, which reaches the expected performce specification.