AIC1647
White LED Step-Up Converter in SOT23
FEATURES
1.2MHz Fixed Frequency Current-Mode PWM
Operation.
Efficiency Up to 84% at V
IN
=4.2V, 3LEDs,
I
LED
=20mA
Drives Up to 6LEDs in series
Low Supply Current: 70µA
Matches LED Current
Require Tiny Inductors and Capacitors
Tiny SOT23-5 Package
DESCRIPTION
AIC1647 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 the LEDs
provides identical LED currents resulting in
uniform brightness. This configuration eliminates
the need for ballast resistors. Low 95mV
feedback voltage minimizes power loss in the
current setting resistor for better efficiency.
AIC1647 is a step-up PWM converter, which
APPLICATIONS
Cellular Phones
PDAs
Digital Still Cameras
Handheld Devices
White LED Display Backlighting
includes an internal N-channel MOSFET switch
for high efficiency. The high switching frequency,
1.2MHz,
allows
the
use
of
tiny
external
components, saves the layout space and cost.
AIC1647 is available in a space-saving, 5-lead
SOT-23-5 package.
TYPICAL APPLICATION CIRCUIT
3.3~4.2V
C1
1µF
L
6.8µH
VIN
SHDN
GND
FB
SW
D1
C2
1µF
BZV55-B12
11.8V~12.2V
90
V
IN
=4.2V
85
Efficiency (%)
80
75
70
D2
R1
1K
R
FB
4.7Ω
20mA
V
IN
=3.0V
V
IN
=3.6V
AIC1647
L1: 976AS-6R8M, 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 with Over Voltage Protection 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-1647P-03 010405
1
AIC [ ANALOG INTERGRATIONS CORPORATION ]
