S-8540 Datasheet, PDF (1/36 Pages) Seiko Instruments Inc – STEP-DOWN, 600 kHz PWM CONTROL or PWM/PFM SWITCHABLE SWITCHING REGULATOR CONTROLLER

Rev.3.2_00
STEP-DOWN, 600 kHz PWM CONTROL or PWM/PFM SWITCHABLE
SWITCHING REGULATOR CONTROLLER
S-8540/8541 Series
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.
„ Features
• Oscillation frequency
• Output voltage
• Output voltage precision
• Feed back type for output voltage (FB)
• External components:
• Built-in PWM/PFM switchover control
circuit (S-8541 series)
• Current limit circuit
• Soft-start
• Shutdown function
• Small package
• Lead-free products
600 kHz (A, B types)
300 kHz (C, D types)
1.5 to 6.0 V, selectable in 0.1V steps (A, C types)
±2.0%
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 R_SENSE.
Time is set by a capacitor C_SS and a resistor R_SS.
8-Pin MSOP
„ 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.
„ Package
Package Name
8-Pin MSOP
Package
FN008-A
Drawing Code
Tape
FN008-A
Reel
FN008-A
Seiko Instruments Inc.
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