AP1521
White LED Step-Up Converter
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
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.
Applications
- Cellular Phones
- PDAs, Hand-held Computers
- Digital Cameras
- MP3 Players
- GPS Receivers
Pin Assignments
Pin Descriptions
Name
SW
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： R
FB
= 310mV / I
LED
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.
Top View
V
IN
SHDN
V
SS
FB
SW V
SS
FB
SHDN
SOT23-5L
V
IN
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
1/8
ANACHIP [ ANACHIP CORP ]
