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
TSOT-23-6, and SOT-23-6 Packages
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 TSOT-
23-6, and SOT-23-6 packages.
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
SHDN OVP
GND
FB
20mA
75
V
IN
=3.0V
V
IN
=3.6V
70
AIC1648
L1: 976AS-6R8M/D321F, TOKO
D1: RB521S-30, ROHM
C1: JMK107BJ105KA, TAIYO YUDEN
C2: EMK212BJ105KA, TAIYO YUDEN
R
FB
4.7Ω
65
3 LEDs, 6.8µH
L1: 976AS-6R8M, TOKO
D1: RB521S-30, ROHM
60
0
5
10
15
20
LED Current (mA)
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-1648G-01 122608
1
AIC1648
ABSOLUTE MAXIMUM RATINGS
Input Voltage (VIN)
SW Voltage
FB Voltage
6V
33V
6V
6V
34V
–40°C to 85°C
125°C
–65°C to 150°C
260°C
SHDN
Voltage
OVP Voltage
Operating Temperature Range
Maximum Junction Temperature
Storage Temperature Range
Lead Temperature (Soldering, 10 sec)
Absolute Maximum Ratings are those values beyond which the life of a device may be impaired.
TEST CIRCUIT
L1
V
IN
C1
1µF
10µH
VIN
SHDN
GND
SW
OVP
FB
RFB
4.7Ω
I
LED
D1
C2
0.22µF
AIC1648
L1: 976AS-100M, TOKO
D1: RB521S-30, ROHM
C1: JMK107BJ105KA, TAIYO YUDEN
C2: EMK212BJ224KG, TAIYO YUDEN
3
AIC1648
ELECTRICAL CHARACTERISTICS
(V
SHDN
=3V, V
IN
=3V, T
A
=25°C, unless otherwise specified.) (Note 1)
°
PARAMETER
Minimum Operating Voltage
Maximum Operating Voltage
SYMBOL
V
IN
V
IN
Switching
Supply Current
I
IN
Non switching
V
SHDN
= 0V
ERROR AMPLIFIER
Feedback Voltage
FB Input Bias Current
OSCILLATOR
Switching Frequency
Maximum Duty Cycle
POWER SWITCH
SW ON Resistance
Switch Leakage Current
CONTROL INPUT
R
DS(ON)
I
SW(OFF)
V
SW
=33V
1.4
0.1
5
1
Ω
µA
f
OSC
DC
0.8
85
1.2
90
1.6
MHz
%
V
FB
I
FB
V
FB
=95mV
85
95
1
105
mV
nA
1
70
0.1
TEST CONDITIONS
MIN
2.5
5.5
5
100
µA
1.0
TYP
MAX
UNIT
V
V
mA
SHDN
Voltage High
SHDN
Voltage Low
OVER VOLTAGE PROTECTION
OVP Input Resistance
OVP Threshold
V
IH
V
IL
ON
OFF
1.5
0.3
V
V
R
OVP
V
OVP
1V Hysteresis typical
0.6
22
1.2
27
1.8
32
MΩ
V
Note 1: Specifications are production tested at T
A
=25°C. Specifications over the -40°C to 85°C operating
temperature range are assured by design, characterization and correlation with Statistical Quality
Controls (SQC).
4
AIC1648
TYPICAL PERFORMANCE CHARACTERISTICS
1.6
Switching Frequency (MHz)
95.0
Feedback Voltage (mV)
1.4
94.5
94.0
93.5
93.0
92.5
92.0
-50
1.2
1.0
0.8
0.6
Temperature (°C)
Fig. 2 Feedback Voltage vs. Temperature
0
50
100
150
0.4
-50
Fig. 3
Temperature (°C)
Switching Frequency vs. Temperature
0
50
100
150
70
1.6
FB=GND
60
FB=V
IN
50
Supply Current (mA)
Supply Current (µA)
1.4
1.2
1.0
40
0.8
Non-Switching
30
2
0.6
6
Switching
2
Supply Voltage (V)
Fig. 4 Supply Current vs. Supply Voltage
3
4
5
Fig. 5
Supply Voltage (V)
Supply Current vs. Supply Voltage
3
4
5
6
1.4
100
1.3
I
LED_DUTY
/ I
LEDMAX
(%)
80
V
IN
=3.6V; L=10µH
C
IN
=1µF, C
OUT
=0.22µF
3LEDs
R
DS-ON
(Ω)
1.2
60
1.1
100Hz
& 200Hz
40
1.0
500Hz
20
0.9
1KHz
2KHz
20
40
3KHz
60
80
100
0.8
2.5
3.0
3.5
4.0
4.5
5.0
5.5
6.0
0 0
Supply Voltage (V)
Fig. 6 R
DS-ON
vs. Supply Voltage
SHDN
PIN PWM Duty (%)
Fig. 7
Dimming Control by Shutdown PIN
5
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