The AP1503 series are monolithic ICs designed for step-down DC/DC converters, and own the ability of driving a 2.5A load without additional transistor components. Due to reducing the number of external component, the board space can be saved easily. The external shutdown function can be controlled by logic level and then come into standby mode. The external compensation makes feedback control have good line and load regulation. Regarding protected function, thermal shutdown is to prevent over temperature operating from damage, and current limit is against over current operating of the output switch. The AP1503 series operates at a switching frequency of 300KHz thus allowing smaller sized filter components than what would be needed with lower frequency switching regulators. Other features include a guaranteed +2% tolerance on output voltage under specified input voltage and output load conditions, and +15% on the oscillator frequency. The output version included fixed 3.3V, 5V. The packages are available in a standard SOP-7 lead package.