AIC AIC1647PVTR

AIC1647
White LED Step-Up Converter in SOT23
FEATURES
DESCRIPTION
1.2MHz Fixed Frequency Current-Mode PWM
Operation.
AIC1647 is a fixed frequency step-up DC/DC
Efficiency Up to 84% at VIN=4.2V, 3LEDs,
ILED=20mA
Drives Up to 6LEDs in series
constant current to provide backlight in hand-
converter designed to drive white LEDs with a
held devices. Series connection of the LEDs
provides identical LED currents resulting in
Low Supply Current: 70µA
Matches LED Current
Require Tiny Inductors and Capacitors
Tiny SOT23-5 Package
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
includes an internal N-channel MOSFET switch
for high efficiency. The high switching frequency,
Cellular Phones
PDAs
Digital Still Cameras
Handheld Devices
White LED Display Backlighting
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
C1
1µF
L
90
D1
VIN=4.2V
6.8µH
VIN
SW
BZV55-B12
11.8V~12.2V
SHDN
GND
C2
1µF
FB
D2
20mA
R1
AIC1647
85
Efficiency (%)
3.3~4.2V
80
VIN=3.6V
VIN=3.0V
75
70
3 LEDs, 6.8µH
L1: 976AS-6R8M, TOKO
D1: RB521S-30, ROHM
C1: JMK107BJ105KA, TAIYO YUDEN
C2: EMK212BJ105KA, TAIYO YUDEN
1K
RFB
4.7Ω
L1: 976AS-6R8M, TOKO
65
D1: RB521S-30, ROHM
60
0
5
10
LED Current (mA)
15
20
Fig. 1 Li-Ion Powered Driver with Over Voltage Protection for Three White LEDs
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.
TEL: 886-3-5772500
FAX: 886-3-5772510
www.analog.com.tw
1
AIC1647
ORDERING INFORMATION
AIC1647XXXX
ORDER NUMBER
PACKING TYPE
TR: TAPE & REEL
BG: BAG
AIC1647CV&PV
(SOT-23-5)
PIN CONFIGURATION
FRONT VIEW
VIN
SHDN
5
4
PACKAGE TYPE
V: SOT-23-5
C: Commercial
P: Lead Free Commercial
Example:
1
2
3
SW GND FB
AIC1647CVTR
in SOT-23-5 Package & Tape &
Reel Packing Type
MARKING
Part No.
CV
PV
AIC1647
1647
1647P
ABSOLUTE MAXIMUM RATINGS
Input Voltage (VIN)
6V
SW Voltage
33V
FB Voltage
6V
SHDN Voltage
6V
–40°C to 85°C
Operating Temperature Range
125°C
Maximum Junction Temperature
–65°C to 150°C
Storage Temperature Range
Lead Temperature (Soldering, 10 sec)
260°C
Absolute Maximum Ratings are those values beyond which the life of a device may be impaired.
TEST CIRCUIT
L1
VIN
C1
1µF
D1
10µH
VIN
C2
SW
BZV55-B12
11.8V~12.2V
SHDN
GND
0.22µF
D2
FB
AIC1647
L1: 976AS-100M, TOKO
D1: RB521S-30, ROHM
C1: JMK107BJ105KA, TAIYO YUDEN
C2: EMK212BJ224KG, TAIYO YUDEN
ILED
R1
1K
RFB
4.7Ω
2
AIC1647
ELECTRICAL CHARACTERISTICS
(V SHDN =3V, VIN=3V, TA=25°C, unless otherwise specified.) (Note 1)
PARAMETER
SYMBOL
Minimum Operating Voltage
VIN
Maximum Operating Voltage
VIN
Supply Current
IIN
TEST CONDITIONS
MIN
TYP
MAX
2.5
UNIT
V
5.5
V
mA
Switching
1
5
Non switching
70
100
V SHDN = 0V
0.1
1.0
95
105
µA
ERROR AMPLIFIER
Feedback Voltage
VFB
FB Input Bias Current
IFB
85
VFB=95mV
1
mV
nA
OSCILLATOR
Switching Frequency
fOSC
0.8
1.2
Maximum Duty Cycle
DC
85
90
1.6
MHz
%
POWER SWITCH
SW ON Resistance
RDS(ON)
1.4
5
Ω
Switch Leakage Current
ISW(OFF) VSW=33V
0.1
1
µA
CONTROL INPUT
SHDN Voltage High
VIH
ON
SHDN Voltage Low
VIL
OFF
1.5
V
0.3
V
Note 1: Specifications are production tested at TA=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).
3
AIC1647
TYPICAL PERFORMANCE CHARACTERISTICS
1.6
Switching Frequency (MHz)
Feedback Voltage (mV)
95.0
94.5
94.0
93.5
93.0
92.5
92.0
-50
0
50
100
1.4
1.2
1.0
0.8
0.6
0.4
-50
150
Temperature (°C)
Fig. 2 Feedback Voltage vs. Temperature
0
50
100
Temperature (°C)
Switching Frequency vs. Temperature
Fig. 3
150
1.6
70
Supply Current (mA)
Supply Current (µA)
FB=GND
60
FB=VIN
50
40
Non-Switching
30
2
3
4
5
Supply Voltage (V)
Fig. 4 Supply Current vs. Supply Voltage
1.0
0.8
6
Switching
2
3
Fig. 5
4
5
6
Supply Voltage (V)
Supply Current vs. Supply Voltage
100
ILED_DUTY / ILEDMAX (%)
1.3
RDSON (Ω)
1.2
0.6
1.4
1.2
1.1
1.0
0.9
0.8
2.5
1.4
3.0
3.5
4.0
4.5
5.0
5.5
Supply Voltage (V)
Fig. 6 RDS-ON vs. Supply Voltage
6.0
VIN=3.6V; L=10µH
CIN=1µF, COUT=0.22µF
3LEDs
80
60
100Hz & 200Hz
40
500Hz
20
0
1KHz
2KHz
0
3KHz
20
40
60
80
100
SHDN PIN PWM Duty (%)
Fig. 7
Dimming Control by Shutdown PIN
4
AIC1647
TYPICAL PERFORMANCE CHARACTERISTICS
(Continued)
90
90
VIN=4.2V
VIN=4.2V
85
85
Efficiency (%)
Efficiency (%)
VIN=3.0V
80
VIN=3.6V
75
3 LEDs, 10µH
70
80
VIN=3.6V
75
VIN=3.0V
4 LEDs, 10µH
70
L1: 976AS-100M, TOKO
L1: 976AS-100M, TOKO
D1: RB521S-30, ROHM
65
65
D1: RB521S-30, ROHM
Test circuit refer to Fig.1
Test circuit refer to Fig.1
60
60
0
5
10
15
20
LED Current (mA)
Fig. 8 3 LEDs Efficiency vs. LED Current
0
5
Fig. 9
10
VIN=4.2V
VIN=4.2V
75
75
Efficiency (%)
Efficiency (%)
80
VIN=3.6V
VIN=3.0V
70
5 LEDs, 10µH
L1: 976AS-100M, TOKO
65
VIN=3.6V
70
VIN=3.0V
6 LEDs, 10µH
65
L1: 976AS-100M, TOKO
D1: RB521S-30, ROHM
Test circuit refer to Fig.1
0
5
10
15
D1: RB521S-30, ROHM
Test circuit refer to Fig.1
60
20
LED Current (mA)
Fig. 10 5 LEDs Efficiency vs. LED Current
0
80
Efficiency (%)
Efficiency (%)
VIN=4.2V
D1: RB521S-30, ROHM
Test circuit refer to Fig.1
75
80
VIN=3.6V
3 LEDs, 6.8µH
70
15
L1: 976AS-6R8M, TOKO
85
VIN=3.0V
10
LED Current (mA)
6 LEDs Efficiency vs. LED Current
6 LEDs, 6.8µH
VIN=4.2V
75
5
Fig. 11
90
L1: 976AS-6R8M, TOKO
VIN=3.6V
70
VIN=3.0V
65
D1: RB521S-30, ROHM
Test circuit refer to Fig.1
65
60
20
80
85
60
15
LED Current (mA)
4 LEDs Efficiency vs. LED Current
0
5
10
15
20
LED Current (mA)
Fig. 12 3 LEDs Efficiency vs. LED Current
60
0
Fig. 13
5
10
15
LED Current (mA)
6 LEDs Efficiency vs. LED Current
5
AIC1647
TYPICAL PERFORMANCE CHARACTERISTICS
(Continued)
VSHDN, 2V/div
VSHDN, 2V/div
VOUT, 2V/div
IINDUCTOR, 100mA/div
IINDUCTOR, 100mA/div
VOUT, 20V/div
VIN=3.6V; 3 LEDs; L1=10µF; COUT=0.22µF; ILED=20mA
Fig. 14
VIN=3.6V; 6 LEDs; L1=10µF; COUT=0.22µF; ILED=10mA
Start-Up from Shutdown
Fig. 15
Start-Up from Shutdown
11.0
10.5
Output Voltage (V)
VOUT, 100mV/div
IINDUCTOR, 100mA/div
10.0
9.5
9.0
8.0
6 Samples' Temperature Data
7.5
VSW , 10V/div
7.0
-40
-20
0
20
40
60
80
Temperature (°C)
Fig. 17 Output voltage vs. temperature
VIN=3.6V; 3 LEDs; L1=10µF; COUT=0.22µF; ILED=10mA
Fig. 16
3 LEDs
ILED=20mA
8.5
Operation Wave Form
100
LED Current (mA)
25
20
15
VIN=4.2V
10 V =3.6V
IN
5
VIN=3.3V
VIN=2.5V
0
-80
-60
-40
4 LEDs
-20
0
20
40
60
80
Temperature (°C)
Fig. 18 LED Current vs. Temperature
100
6
AIC1647
BLOCK DIAGRAM
VIN
SHDN
95mV
VREF
PWM/PFM
Control
+
FB
SW
Error
AMP.
Control
Logic
+
-
-
RC
Driver
M1
PWM
Comparator
CC
Slope
Internal
Soft Start
1.2MHz
Compensation Oscillator
Current AMP
+
RS
-
GND
PIN DESCRIPTIONS
PIN 1: SW
- Switch
Pin.
Connect
inductor/diode here. Minimize
trace area at this pin to reduce
EMI.
PIN 2: GND
- Ground Pin. Tie directly to local
ground plane.
PIN 3: FB
- Feedback
Pin.
Reference
voltage is 95mV. Connect
cathode of lowest LED and
resistor here. Calculate resistor
value according to the formula:
RFB = 95mV/ILED
PIN 4: SHDN - Shutdown pin. Tie to higher than
1.5V to enable device, 0.3V or
less to disable device.
PIN 5: VIN
- Power input pin. Bypass VIN to
GND with a capacitor sitting as
close to VIN as possible.
7
AIC1647
APPLICATION INFORMATION
Inductor Selection
Open-Circuit Protection
A 10µH inductor is recommended for most
AIC1647 applications. Although small size and
high efficiency are major concerns, the inductor
should have low core losses at 1.2MHz and low
DCR (copper wire resistance).
In the cases of output open circuit, when the LEDs
are disconnected from the circuit or the LEDs fail,
the feedback voltage will be zero. AIC1647 will
then switch to a high duty cycle resulting in a high
output voltage, which may cause SW pin voltage
to exceed its maximum 33V rating. A zener diode
can be used at the output to limit the voltage on
SW pin (Figure 1). The zener voltage should be
larger than the maximum forward voltage of the
LED string. The current rating of the zener should
be larger than 0.1mA.
Capacitor Selection
The small size of ceramic capacitors makes them
ideal for AIC1647 applications. X5R and X7R
types are recommended because they retain their
capacitance over wider ranges of voltage and
temperature than other types, such as Y5V or
Z5U. 1µF input capacitor with 1µF output
capacitor are sufficient for most AIC1647
applications.
Diode Selection
Schottky diodes, with their low forward voltage
drop and fast reverse recovery, are the ideal
choices for AIC1647 applications. The forward
voltage drop of a Schottky diode represents the
conduction losses in the diode, while the diode
capacitance (CT or CD) represents the switching
losses. For diode selection, both forward voltage
drop and diode capacitance need to be
considered. Schottky diodes with higher current
ratings usually have lower forward voltage drop
and larger diode capacitance, which can cause
significant switching losses at the 1.2MHz
switching frequency of AIC1647. An Schottky
diode rated at 100mA to 200mA is sufficient for
most AIC1647 applications.
LED Current Control
LED current is controlled by feedback resistor
(RFB in Fig. 1). The feedback reference voltage is
95mV. The LED current is 95mV/ RFB. In order to
have accurate LED current, precision resistors are
preferred (1% recommended). The formula for RFB
selection is shown below.
RFB = 95mV/ILED
Dimming Control
There are three different ways of dimming control
circuits as follows:
1. Using a PWM Signal
PWM brightness control provides the widest
dimming range by pulsing the LEDs on and off at
full and zero current, respectively. The change of
average LED current depends on the duty cycle of
the PWM signal. Typically, a 0.1kHz to 1kHz
PWM signal is used. Two applications of PWM
dimming with AIC1647 are shown in Figure 19
and Figure 20. One, as Figure 19, uses PWM
signal to drive SHDN pin directly for dimming
control. The other, as Figure 20, employs PWM
signal going through a resistor to drive FB pin. If
the SHDN pin is used, the increase of duty cycle
results in LED brightness enhancement. If the FB
pin is used, on the contrary, the increase of duty
cycle will decrease its brightness. In this
application, LEDs are dimmed by FB pin and
turned off completely by SHDN .
2. Using a DC Voltage
For some applications, the preferred method of a
dimming control uses a variable DC voltage to
adjust LED current. The dimming control using a
DC voltage is shown in Figure 21. Cautiously
selecting R1 and R2 is essential so that the
current from the variable DC source is much
smaller than the LED current and much larger
8
AIC1647
than the FB pin bias current. With a VDC ranging
from 0V to 5V, the selection of resistors in Figure
21 results in dimming control of LED current from
20mA to 0mA, respectively.
D1
L1
VIN
C1
1µF
PWM
3. Using a Filtered PWM Signal
Filtered PWM signal can be considered as an
adjustable DC voltage. It can be used to replace
the variable DC voltage source in dimming
control. The circuit is shown in Figure 22.
RB512S-30
10µH
VIN
C2
SW
BZV55-B12
11.8V~12.2V
SHDN
GND
1µF
D2
FB
20mA
R1
AIC1647
1K
RFB
4.7Ω
Fig. 19 Dimming Control Using a PWM Signal with Open-Circuit Protection
D1
L1
VIN
C1
1µF
RB512S-30
10µH
VIN
C2
SW
BZV55-B12
11.8V~12.2V
SHDN
GND
1µF
D2
20mA
FB
AIC1647
PWM
R2
R1
51K
1K
RFB
4.7Ω
Fig. 20 Dimming Control Using a PWM Signal
9
AIC1647
D1
L1
VIN
C1
1µF
RB512S-30
10µH
VIN
C2
SW
1µF
D2
BZV55-B12
11.8V~12.2V
SHDN
GND
20mA
FB
AIC1647
0~5VDC
R2
R1
51K
1K
RFB
4.7Ω
Fig. 21 Dimming Control Using a DC Voltage
D1
L1
VIN
C1
1µF
RB512S-30
10µH
VIN
C2
SW
1µF
D2
BZV55-B12
11.8V~12.2V
SHDN
20mA
FB
GND
AIC1647
R3
PWM
5.1K
R2
R1
51K
1K
C3
0.1µF
RFB
4.7Ω
Fig. 22 Dimming Control Using a Filter PWM Signal
APPLICATION EXAMPLE
D1
L
VIN
C1
1µF
10µH
VIN
SW
C2
1µF
RB521S-30
SHDN
20mA
GND
FB
AIC1647
R2
1K
RFB
R1
4.7Ω
4.7Ω
Fig. 23 Six white LEDs application in Li-Ion Battery
10
AIC1647
PHYSICAL DIMENSIONS (unit: mm)
SOT-23-5
D
A
A
E
E1
S
Y
M
B
O
L
e
e1
SEE VIEW B
WITH PLATING
MIN.
MAX.
A
0.95
1.45
A1
0.05
0.15
A2
0.90
1.30
b
0.30
0.50
c
0.08
0.22
3.00
D
2.80
E
2.60
3.00
E1
1.50
1.70
e
0.95 BSC
e1
1.90 BSC
c
A
A2
b
SOT-25
MILLIMETERS
SECTION A-A
A1
BASE METAL
L
0.60 REF
0°
8°
0.25
θ
0.60
0.30
L1
GAUGE PLANE
SEATING PLANE
θ
L
L1
VIEW B
Note:
Information provided by AIC is believed to be accurate and reliable. However, we cannot assume responsibility for use of any circuitry other
than circuitry entirely embodied in an AIC product; nor for any infringement of patents or other rights of third parties that may result from its
use. We reserve the right to change the circuitry and specifications without notice.
Life Support Policy: AIC does not authorize any AIC product for use in life support devices and/or systems. Life support devices or systems
are devices or systems which, (I) are intended for surgical implant into the body or (ii) support or sustain life, and whose failure to perform,
when properly used in accordance with instructions for use provided in the labeling, can be reasonably expected to result in a significant
injury to the user.
11