Diodes AP5725 - Manual

AP5725
WHITE LED STEP-UP CONVERTER
AP5725
Document number: DS31844 Rev. 3 - 2
1 of 17
www.diodes.com
July 2010
© Diodes Incorporated
Description
The AP5725 is a step-up DC/DC converter specifically
designed to drive white LEDs with a constant current. The
device can drive 2 ~ 6 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. For driving higher number of LEDs,
AP5725 also supports a single feedback of parallel
connected multiple strings of equal number of LEDs.
The AP5725 switches at 1.2MHz that allows the use of tiny
external components. A low 0.25V feedback voltage
minimizes power loss in the current setting resistor for better
efficiency.
Pin Assignments
1
2
3 74
6
OVP
FB
5
EN
SW
(Top View)
V IN
GND
SOT26 / TSOT23-6
SW
V
IN
OVP
1
2
3
6
5
4
GND
FB
EN
(Top View)
DFN2020C-6
Features
• High efficiency: 84% typical
• Fast 1.2MHz switching frequency
• Current limit and UVLO protections
• Internal thermal shutdown
• Internal Over Voltage Protection
• Integrated soft-start function
• SOT26, TSOT23-6 and DFN2020C-6: Available in
“Green” Molding Compound (No Br, Sb)
• Lead Free Finish/ RoHS Compliant (Note 1)
Applications
• Cellular
Phones
• PDAs, Hand held Computers
• Digital
Cameras
• MP3 Players
• GPS Receivers
Notes: 1. EU Directive 2002/95/EC (RoHS). All applicable RoHS exemptions applied. Please visit our website at
http://www.diodes.com/products/lead_free.html.
Typical Application Circuit
V
IN
SW
EN
GND
FB
AP5725
C
OUT
1uF
R
SET
12
L1
22uH
D1
V
IN
C
IN
1uF
OVP
2~6 LEDs
PWM Dimming
OFF ON
Figure 1. Typical Application Circuit