Abstract: By using SMIC 180 nm BCD process, a low-ripple, high-conversion efficiency pre-modulation architecture switch capacitor boost DC-DC converter circuit chip was designed and implemented. The chip circuit realizes the low output voltage ripple in the full load range by using the on-resistance analog pre-modulation method. At the same time, the switching frequency regulation circuit under light load circuit achieves high conversion efficiency under light load. In order to ensure the safe start of the chip, the constant current starting circuit is designed. The chip is implemented and measurement. The test results show that under the input voltage range of 2.8 - 5.0 V, only one fly capacitor in the switching frequency of 1.2 MHz realizes the output ripple of 27 mV with output current of 120 mA, output voltage of 5.0 V, and the ripple ratio is only 0.54%. The chip peak efficiency is 91.95%. Compared with the traditional methods of resistive, capacitive or multiphase parallel modulation, the proposed single-phase modulation scheme is more simple and more reliable.