STEP-DOWN, BUILT-IN FET, SYNCHRONOUS

Seiko Instruments Inc.

1

The S-8550/8551 Series is a CMOS synchronous rectification step-down

switching regulator which mainly consists of a reference voltage circuit, an

oscillator, an error amplifier, a phase compensation circuit, a PWM controller, an

under voltage lockout circuit (UVLO), a current limit circuit, and a power MOS

FET. The oscillation frequency is high at 1.2 MHz, so a high efficiency, large

output current, step-down switching regulator can be achieved by using small

external parts.

The built-in synchronous rectification circuit makes achieving high efficiency

easier compared with conventional step-down switching regulators. A ceramic

capacitor can be used as an output capacitor.

High-density mounting is

supported by adopting a small SOT-23-5 package.

The S-8550 and S-8551 Series are offered according to different pin configuration.

Features

• Oscillation frequency :

1.2 MHz

• Input voltage range :

2.0 to 5.5 V

• Output voltage range :

Arbitrarily settable by external output voltage setting resistor

• Output current :

600 mA

• Reference voltage :

0.6 V

±2.0%

• Efficiency :

92%

• Soft-start function :

1 ms typ.

• Shutdown function :

Shutdown current consumption : 1.0

µA max.

• Built-in current limit circuit

• Pch power MOS FET on-resistance :

0.4

Ω typ.

• Nch power MOS FET on-resistance :

0.3

Ω typ.

• Constant continuous mode operation (no light load mode)

• Small package :

SOT-23-5

• Lead-free products

Applications

• Mobile devices, such as mobile phones, Bluetooth devices, wireless devices, digital audio players, digital still

cameras, portable DVD players, and portable CD players

Package

Drawing Code

Package Name

Package

Tape

Reel

SOT-23-5

MP005-A

MP005-A

MP005-A