This paper presents a DC-DC boost converter for energy harvesting. The time-domain maximum power point tracking (MPPT) technique implements to maximize the source's energy harvesting performance with no additional switch and time slot. Furthermore, it is implementing digital self-tracking zero current detectors (ST-ZCD) for high efficiency. This DC-DC boost converter fabricates with a 180nm CMOS process. The input voltage of the boost converter ranges from 0.2 to 0.7V and generates the output voltage of 1.2V. The total area of this converter with the MPPT operation is 600 μm x 475 μm. The measured power conversion efficiency of this DC-DC boost converter is 85.5%.