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The S-8520/8521 series consists of CMOS step-down switching regulator (DC/DC Converter ICs)-controllers with PWM-control (S-8520) and PWM/PFM-switched control (S-8521). These devices contain a reference voltage source, oscillation circuit, error amplifier, and other components.
The S-8520 series provides low-ripple power, high-efficiency, and excellent transient characteristics thanks to a PWM control circuit capable of varying the duty ratio linearly from 0% up to 100%. The series also contains an error amplifier circuit as well as a soft-start circuit that prevents overshoot at startup.
The S-8521 series works with either PWM control or PFM control, and can switch from one to the other. It normally operates using PWM control with a duty ratio of 25% to 100%, but under a light load, it automatically switches to PFM control with a duty ratio of 25%. This series ensures high efficiency over a wide range of conditions, from standby mode to operation of peripheral equipment.
With the addition of an external Pch Power MOS FET or PNP transistor, a coil, capacitors, and a diode connected externally, these ICs can function as step-down switching regulators (DC/DC Converter ICs). They serve as ideal power supply units for portable devices when coupled with the SOT-23-5 minipackage, providing such outstanding features as low current consumption. Since this series can accommodate an input voltage of up to 16V, it is also ideal when operating via an AC adapter.