UNISONIC TECHNOLOGIES CO., LTD

UC3550

CMOS IC

www.unisonic.com.tw

1 of 10

Copyright © 2005 Unisonic Technologies Co., Ltd

QW-R502-082,A

PWM CONTROLLED，

PWM/PFM SWITCHABLE

STEP-UP DC-DC CONTROLLER

DESCRIPTION

The UTC UC3550 series is a compact, high efficiency, step-up

DC/DC controllers includes an error amplifier, oscillator, PWM

comparator, skip cycle comparator, voltage reference, soft-start,

and high speed lower ON-resistance driver for driving external

power devices (NMOS or NPN) ,Additionally, a CE (chip enable)

function that reduces power consumption during shut-down mode.

That typically operated from a single-or dual-cell battery packs. It

have a driver pin ,ext pin, for connecting to an external transistor

（

NMOS or NPN）. a lower ON-resistance external transistor can

obtain larger output current. With only external components, this

series allow a simple means to accommodate high output current

applications.

The UTC UC3550 series goes automatically into skip switching

cycles under light load condition to maintain high efficiency.

FEATURES

* Input voltage range：0.9~8V

* Output voltage range：1.8~6V programmable in 0.1V with high

accuracy ± 2.5%

* High efficiency 88%（typ.）

* Oscillator frequency: 300kHz.（±20%）

* Chip enable pin with pull-up current source

SOT-25

4

5

3

2

1

*Pb-free plating product number: UC3550L

ORDERING INFORMATION

Order Number

Normal

Lead Free Plating

Package

Packing

UC3550-xx-AF5-R

UC3550L-xx-AF5-R

SOT-25

Tape Reel

UC3550L-xx-AF5-R

(1)Packing Type

(2)Package Type

(4)Lead Plating

(1) R: Tape Reel

(2) AF5: SOT-25

(4) L: Lead Free Plating, Blank: Pb/Sn

(3) xx: reference to Marking Information

(3)Voltage Code