Document
UNISONIC TECHNOLOGIES CO., LTD
UC3551
Preliminary
ADVANCED PWM STEP-UP DC-DC CONVERTER
CMOS IC
DESCRIPTION
The UTC UC3551 is a step-up DC/DC converter with high efficiency and low start-up voltage. It is operaded in stable waveforms without external compensate. This device incorporates an adaptive current mode PWM control loop in which an error amplifier, ramp generator, comparator, switch pass element and driver are included. Besides, this circuit provides a stable and high efficient operation over a wide range of load currents.
The UTC UC3551 features high switching rate which is up to 450 KHz, making the external component counts less required. Moreover, it features 17μA low quiescent current, which makes the battery life longer. The low start-up input voltage below 1V makes UTC UC3551 suitable for 1 to 4 battery cells applications of providing up to 300mA output current.
Two external resistors determine the value of the output voltage. The external power devices (NMOS or NPN) are derived by both internal 2A switch and driver.
The UTC UC3551 is intended to be used in PDA, DSC, LCD Panel, RF-Tags, MP3, portable instrument and wireless equipment.
FEATURES
* Low Start-up Input Voltage is as Low as 1.0V * Efficiency up to 90% * High Supply Capability to Deliver 3.3V 100mA with 1 Alkaline Cell * Quiescent (Switch-off) Supply Current: 17µA * Zero Shutdown Mode Supply Current * Fixed Switching Frequency: 450KHz * Both Internal and External Power Switches for Maximum Flexibility
ORDERING INFORMATION
Ordering Number
Lead Free
Halogen Free
UC3551L-AG6-R
UC3551G-AG6-R
Package SOT-26
UC3551L-AG6-R
(1)Packing Type (2)Package Type
(3)Lead Free
(1) R: Tape Reel (2) AG6: SOT-26 (3) G: Halogen Free, L: Lead Free
Packing Tape Reel
www.unisonic.com.tw Copyright © 2011 Unisonic Technologies Co., Ltd
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QW-R502-555.a
UC3551
MARKING INFORMATION
PACKAGE
VOLTAGE CODE
Preliminary
MARKING
SOT-26
AD:ADJ
PIN CONFIGURATION
CMOS IC
PIN DESCRIPTION
PIN NO. 1 2 3 4 5 6
PIN NAME CE EXT GND LX VDD FB
DESCRIPTION Chip enable UC3551 gets into shutdown mode when CE pin set to low. Output pin for driving external NMOS Ground Pin for switching Input positive power pin of UC3551 Feedback input pin Internal reference voltage for the error amplifier is 1.25V.
UNISONIC TECHNOLOGIES CO., LTD
www.unisonic.com.tw
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QW-R502-555.a
UC3551
BLOCK DIAGRAM
LX
GND
EXT
Preliminary
VLx Limiter Buffer
Control Circuit
Vref
+ -
Chip Enable
Over Temp Detector
EN
CMOS IC
VDD FB
UNISONIC TECHNOLOGIES CO., LTD
www.unisonic.com.tw
3 of 6
QW-R502-555.a
UC3551
Preliminary
CMOS IC
ABSOLUTE MAXIMUM RATING
PARAMETER
SYMBOL
RATINGS
UNIT
Supply Voltage LX Pin Switch Voltage
VIN
− 0.3 ~ 7
V
VLX
− 0.3 ~ (VDD + 0.8)
V
Other I/O Pin Voltages LX Pin Switch Current
− 0.3 ~ (VDD + 0.3)
V
ILX 2.5 A
EXT Pin Driver Current Operating Junction Temperature
IEXT TOPR
200 mA 125 °C
Storage Temperature
TSTG
-65~+150
°C
Notes: Absolute.