The S-8520/8521 series is a CMOS step-down switch regulator controller with PWM control (S-8520 series) and PWM/PFM switch control (S-8521 Series). The series has a reference voltage source, an oscillating circuit, an error amplifier and other components, and provides low ripple power, High efficiency and excellent transient characteristics due to the PWM control circuit is able to change duty ratio linearly from 0% to 100%.
Block Diagrams
S-8520 Series
S-8521 Series
The S-8520/8521 series also features a soft starting circuit to prevent overload during startup. The S-8521 series works with PWM control or PFM control. It usually operates with PWM control with duty cycle of 25% to 100%, but under light loads it automatically switches to PFM control with duty cycle of 25%. And the series ensures high efficiency in a variety of equipment conditions from standby mode to operation.
At the same time by adding an external Pch power supply MOS FET or PNP transistor, coil, capacitor and externally connected diode, the S-8520/8521 series can be used as step-down switching regulators, due to the characteristics of small and low current consumption of SOT-23-5, is an ideal choice for portable device power units. With input voltages up to 16v, it is also an ideal choice for AC adapters.
Standard Circuits
