S-8520

S-8520/8521 Series www.sii-ic.com STEP-DOWN, PWM CONTROL or PWM / PFM SWITCHABLE SWITCHING REGULATOR CONTROLLER © SII Semiconductor Corporation, 1997-2010 Rev.9.0_01 The S-8520/8521 Series is a CMOS step-down switching regulator-controller with PWM control (S-8520 Series) and PWM / PFM switching control (S-8521 Series). The S-8520/8521 Series has a reference voltage source, an oscillation circuit, an error amplifier, and other components. The S-8520 Series provides low-ripple power, high efficiency, and excellent transient characteristics due to a PWM control circuit capable of varying the duty ratio linearly from 0% up to 100%. The S-8520/8521 Series also has a soft-start circuit that prevents overshoot at startup. The S-8521 Series works with either PWM control or PFM control. 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%. The S-8520/8521 Series ensures high effi...