© ABLIC Inc., 2000-2010
STEP-DOWN, 600 kHz PWM CONTROL or PWM/PFM
SWITCHABLE SWITCHING REGULATOR CONTROLLER
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.
Output voltage precision
Feed back type for output voltage (FB)
Built-in PWM/PFM switchover control
circuit (S-8541 series)
Current limit circuit
600 kHz (A, B types)
300 kHz (C, D types)
1.5 to 6.0 V, selectable in 0.1V steps (A, C types)
a transistor, a coil, a diode, and capacitors
Duty ratio: 29% (PFM control)
29 to 100% (PWM control)
Current is set by an external resistor RSENSE.
Time is set by a capacitor CSS and a resistor RSS.
*1. Refer to “ Product Name Structure” for details.
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.