S-8540/8541 Series

www.sii-ic.com

STEP-DOWN, 600 kHz PWM CONTROL or PWM/PFM

SWITCHABLE SWITCHING REGULATOR CONTROLLER

© SII Semiconductor Corporation, 2000-2010

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The S-8540/8541 Series is a family of CMOS step-down switching regulator controllers with PWM control (S-

8540 Series) and PWM/PFM switchover control (S-8541 Series). These devices consist of a reference voltage

source, oscillation circuit, an error amplifier, phase compensation circuit, PWM control circuit, current limit

circuit. A high efficiency and large current switching regulator is realized with the help of small external

components due to the high oscillation frequency, 300 kHz and 600 kHz.

The S-8540 Series provides low-ripple voltage, high efficiency, and excellent transient characteristics which

come from the PMW control circuit capable of varying the duty ratio linearly from 0 to 100%, the optimized error

amplifier, and the phase compensation circuit.

The S-8541 Series operates under PWM control when the duty ratio is 29% or higher and operates under PFM

control when the duty ratio is less than 29% to ensure high efficiency over all load range.

These controllers serve as ideal main power supply units for portable devices due to the high oscillation

frequencies together with the small 8-Pin MSOP package.

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Features

• Oscillation frequency

600 kHz (A, B types)

300 kHz (C, D types)

• Output voltage

1.5 to 6.0 V, selectable in 0.1V steps (A, C types)

• Output voltage precision

±2.0%

• Feed back type for output voltage (FB)

• External components:

a transistor, a coil, a diode, and capacitors

• Built-in PWM/PFM switchover control

circuit (S-8541 series)

Duty ratio:

29% (PFM control)

29 to 100% (PWM control)

• Current limit circuit

• Soft-start

• Shutdown function

*1. Refer to “ Product Name Structure” for details.

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Applications

• Power supplies for PDAs, electric organizers, and portable devices.

• Power supplies for audio equipment such as portable CD players and headphone stereos.

• Main or sub Power supplies for notebook computers and peripheral equipment.

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Package

• 8-Pin MSOP