A Novel On-chip Current-Sensing Structure for Current-mode DC-DC Converter

A novel current-sensing structure for current-mode DC-DC converter is presented in this paper. It has significant improvements on current-sensing speed and reducing the sensitivity to the variations of the process, voltage, temperature and loading (PVTL), which is derived in detail. It has been used in a current-mode DC-DC converter fabricated by CSMC 0.5 mu m CMOS process with a die size of 2.25 mm2. Experimental results show that with the current-sensing circuit the converter can operate at the supply voltage range of 2.7 to 5.5V with loading 0-600mA and has the ability to convert from 5.5V down to 0.6V at 4MHz. The measured transient response time is 7 mu s as the load current changes between 0 and 600mA rapidly. Moreover, the current-sensing structure can be also used in other integrated circuits for loop control and over-current protection.