AIC1648
Built-in OVP White LED Step-Up Converter
FEATURES
Built-In Open Circuit Protection
Over Voltage Protection
Efficiency Up to 84% at V
IN
=4.2V, 3LEDs,
I
LED
=20mA
1.2MHz Fixed Switching Frequency
Drives Up to 5LEDs in series
Low Supply Current: 70µA
Matches LED Current
Requires Tiny Inductor and Capacitors
Tiny SOT-23-6 Package
DESCRIPTION
AIC1648 is a fixed frequency step-up DC/DC
converter designed to drive white LEDs with a
constant current to provide backlight in hand-
held devices. Series connection of LEDs
provides identical LED currents resulting in
uniform brightness. This configuration eliminates
the need of ballast resistors. The built-in open
load protection prevents the damage resulting
from an open circuit condition. Low 95mV
feedback voltage minimizes power loss in the
current setting resistor for better efficiency.
APPLICATIONS
Cellular Phones
PDAs
DSCs
Handheld Devices
White LED Display Backlighting
AIC1648 is a step-up PWM converter, which
includes an internal N-channel MOSFET switch
for high efficiency. The high switching frequency,
1.2MHz,
allows
the
use
of
tiny
external
components.
AIC1648 is available in a space-saving, 6-lead
SOT-23-6 package.
TYPICAL APPLICATION CIRCUIT
3.3~4.2V
C1
1µF
L
6.8µH
VIN
SW
D1
C2
1µF
90
V
IN
=4.2V
85
Efficiency (%)
80
75
70
SHDN OVP
GND
FB
R
FB
4.7Ω
20mA
V
IN
=3.0V
V
IN
=3.6V
AIC1648
L1: 976AS-6R8M/D321F, TOKO
D1: RB521S-30, ROHM
C1: JMK107BJ105KA, TAIYO YUDEN
C2: EMK212BJ105KA, TAIYO YUDEN
3 LEDs, 6.8µH
65
L1: 976AS-6R8M, TOKO
D1: RB521S-30, ROHM
60
0
5
LED Current (mA)
10
15
20
Fig. 1 Li-Ion Powered Driver for Three White LEDs
Analog Integrations Corporation
Si-Soft Research Center
3A1, No.1, Li-Hsin Rd. I, Science Park, Hsinchu 300, Taiwan, R.O.C.
TEL: 886-3-5772500
FAX: 886-3-5772510
www.analog.com.tw
DS-1648P-03 010405
1
AIC [ ANALOG INTERGRATIONS CORPORATION ]
