Many modern mobile devices have a touchscreen and are powered by a rechargeable battery. To extend battery usage time before recharge, harvesting energy from ambient light provides an elegant solution if the photovoltaic (PV) modules can be integrated with mobile devices . However, mobile devices are frequently finger operated and/or in motion, so light-harvesting should consider fast-changing shading and partial shading problems. Previous IC works [2-4] have reported on the implementation of maximum power point tracking (MPPT) for light-harvesting, none of them have concurrently addressed these two problems. Although one of these works  considered the mobile device issue, it targets high MPPT steady-state accuracy without considering fast-changing shading problem. Hence, there is still room for improvement with respect to short MPPT transient time to harvest more energy for extending battery usage time.