It is well-known that ultra-low-power three-phase elements, such as ultra-small-size permanent-magnet brushless motor drivers, have been widely used in the consumer products. In order to reduce the cost, size and power consumption of products, it is necessary to integrate the system functions with square-wave PWM (SWPWM) driver in the system-on-chip (SOC) implementation. It follows that, the driver loss and loss distribution are the main challenges in the integration of ultra-low-power SWPWM driver where the driver loss include conducting loss, switching loss and gate driving loss, where the last one is often neglected in other low-, medium- and high-power drivers. On the other hand, there are 16 types and 64 types in 120-degree SWPWM and 180-degree SWPWM, respectively, and the resulting driver loss and loss distribution differ from each other. This paper studies the driver loss and loss distributions of all SWPWM types in detail. The result shows that SWPWM type-01- 01, type-10-10 and type-010-010 are the recommended types in the SOC integration of ultra-low-power SWPWM driver.