AP1521 Datasheet, PDF (1/8 Pages) Anachip Corp – White LED Step-Up Converter

White LED Step-Up Converter
AP1521
„ Features
- Inherently Matched LED Current
- Drives Up to Four LEDs from a 3.2V Supply
- Drives Up to Six LEDs from a 5V Supply
- High Efficiency: 84% Typical
- Fast 1MHz Switching Frequency
- 36V Rugged Bipolar Switch
- Low Profile SOT23-5 Pb-Free Packaging
„ Applications
- Cellular Phones
- PDAs, Hand-held Computers
- Digital Cameras
- MP3 Players
- GPS Receivers
„ Pin Assignments
Top View
V_IN
SHDN
SW V_SS FB
SOT23-5L
„ General Description
The AP1521 is a step-up DC/DC converter
specifically designed to drive white LEDs with a
constant current. The device can drive two, three or
four LEDs in series from a Li-Ion cell. Series
connection of the LEDs provides identical LED
currents resulting in uniform brightness and
eliminates the need for ballast resistors. The
AP1521 switches at 1MHz that allows the use of
tiny external components. A low 300mV feedback
voltage minimizes power loss in the current setting
resistor for better efficiency.
„ Pin Descriptions
Name
SW
V_SS
FB
SHDN
V_IN
Description
Switch Pin. Connect inductor/diode
here. Minimize trace area at this pin
to reduce EMI.
GND pin
Feedback Pin. Reference voltage is
310mV. Connect cathode of lowest
LED and resistor here. Calculate
resistor value according to the
formula： RFB = 310mV / ILED
Shutdown Pin. Tie to 1.5V or higher
to enable the device；0.4V or less to
disable the device.
Input Supply Pin. Must be locally
bypassed.
„ Ordering Information
AP1521 X X
Package
W: SOT23-5L
Packing
Blank : Tube
A : Taping
This datasheet contains new product information. Anachip Corp. reserves the rights to modify the product specification without notice. No liability is assumed as a result of the use of
this product. No rights under any patent accompany the sale of the product.
Rev. 0.1 Apr. 27, 2004
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