AIC1647
White LED Step-Up Converter in SOT23


Analog Integrations Corporation Si-Soft Research Center DS-1647P-03 010405
3A1, No.1, Li-Hsin Rd. I, Science Park, Hsinchu 300, Taiwan, R.O.C.
null FEATURES
null 1.2MHz Fixed Frequency Current-Mode PWM
Operation.
null Efficiency Up to 84% at VIN=4.2V, 3LEDs,
I
LED
=20mA
null Drives Up to 6LEDs in series
null Low Supply Current: 70µA
null Matches LED Current
null Require Tiny Inductors and Capacitors
null Tiny SOT23-5 Package


null APPLICATIONS
null Cellular Phones
null PDAs
null Digital Still Cameras
null Handheld Devices
null White LED Display Backlighting
null 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
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.


null
TYPICAL APPLICATION CIRCUIT



L
6.8µH
D1
SW
VIN
SHDN
FB
GND
AIC1647
3.3~4.2V
R
FB

4.7Ω
C1
1µF
C2
1µF
20mA
L1: 976AS-6R8M, TOKO
D1: RB521S-30, ROHM
C1: JMK107BJ105KA, TAIYO YUDEN
C2: EMK212BJ105KA, TAIYO YUDEN
BZV55-B12
11.8V~12.2V
R1
1K
D2
LED Current (mA)
Ef
fi
ci
e
n
cy (
%
)

0510 15 20
60
65
70
75
80
85
90
V
IN
=3.6V
V
IN
=4.2V
V
IN
=3.0V
3 LEDs, 6.8µH
L1: 976AS-6R8M, TOKO
D1: RB521S-30, ROHM



Fig. 1 Li-Ion Powered Driver with Over Voltage Protection for Three White LEDs

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