AIC AIC1648 Built-in ovp white led step-up converter Datasheet

AIC1648
Built-in OVP White LED Step-Up Converter
FEATURES
DESCRIPTION
Built-In Open Circuit Protection
Over Voltage Protection
AIC1648 is a fixed frequency step-up DC/DC
converter designed to drive white LEDs with a
Efficiency Up to 84% at VIN=4.2V, 3LEDs,
ILED=20mA
1.2MHz Fixed Switching Frequency
Drives Up to 5LEDs in series
constant current to provide backlight in handheld devices. Series connection of LEDs
provides identical LED currents resulting in
uniform brightness. This configuration eliminates
Low Supply Current: 70µA
Matches LED Current
Requires Tiny Inductor and Capacitors
Tiny SOT-23-6 Package
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
AIC1648 is a step-up PWM converter, which
Cellular Phones
PDAs
DSCs
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.
AIC1648 is available in a space-saving, 6-lead
SOT-23-6 package.
TYPICAL APPLICATION CIRCUIT
C1
1µF
90
D1
L
VIN=4.2V
6.8µH
VIN
C2
1µF
SW
SHDN OVP
GND
20mA
FB
AIC1648
85
Efficiency (%)
3.3~4.2V
80
VIN=3.6V
VIN=3.0V
75
70
3 LEDs, 6.8µH
L1: 976AS-6R8M/D321F, TOKO
D1: RB521S-30, ROHM
C1: JMK107BJ105KA, TAIYO YUDEN
C2: EMK212BJ105KA, TAIYO YUDEN
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 for Three White LEDs
Analog Integrations Corporation
Si-Soft Research Center
DS-1648P-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
AIC1648
ORDERING INFORMATION
AIC1648XXXX
ORDER NUMBER
PACKING TYPE
TR: TAPE & REEL
BG: BAG
AIC1648CG&PG
(SOT-23-6)
PIN CONFIGURATION
FRONT VIEW
VIN OVP SHDN
6
5
4
1
2
3
PACKAGE TYPE
G: SOT-23-6
C: COMMERCIAL
P: LEAD FREE COMMERCIAL
Example:
SW GND FB
AIC1648CGTR
in SOT-23-6 Package & Tape & Reel Packing Type
MARKING
Part No.
CG
PG
AIC1648
1648
1648P
ABSOLUTE MAXIMUM RATINGS
Input Voltage (VIN)
6V
SW Voltage
33V
FB Voltage
6V
SHDN Voltage
6V
OVP Voltage
34V
–40°C to 85°C
Operating Temperature Range
Maximum Junction Temperature
125°C
–65°C to 150°C
Storage Temperature Range
260°C
Lead Temperature (Soldering, 10 sec)
Absolute Maximum Ratings are those values beyond which the life of a device may be impaired.
TEST CIRCUIT
D1
L1
VIN
C1
1µF
10µH
VIN
SHDN
GND
C2
0.22µF
SW
OVP
ILED
FB
AIC1648
L1: 976AS-100M, TOKO
D1: RB521S-30, ROHM
C1: JMK107BJ105KA, TAIYO YUDEN
C2: EMK212BJ224KG, TAIYO YUDEN
RFB
4.7Ω
2
AIC1648
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
OVER VOLTAGE PROTECTION
OVP Input Resistance
ROVP
OVP Threshold
VOVP
1V Hysteresis typical
0.6
1.2
1.8
MΩ
22
27
32
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
AIC1648
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
4
5
Supply Voltage (V)
Supply Current vs. Supply Voltage
Fig. 5
6
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
1KHz
2KHz
0 0
Fig. 7
3KHz
20
40
60
80
SHDN PIN PWM Duty (%)
100
Dimming Control by Shutdown PIN
4
AIC1648
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
85
10
20
90
VIN=4.2V
VIN=4.2V
85
75
Efficiency (%)
80
Efficiency (%)
15
LED Current (mA)
4 LEDs Efficiency vs. LED Current
VIN=3.6V
VIN=3.0V
70
5 LEDs, 10µH
80
VIN=3.0V
75
3 LEDs, 6.8µH
70
L1: 976AS-100M, TOKO
65
L1: 976AS-6R8M, TOKO
D1: RB521S-30, ROHM
Test circuit refer to Fig.1
60
5
10
15
D1: RB521S-30, ROHM
Test circuit refer to Fig.1
65
60
0
VIN=3.6V
20
LED Current (mA)
Fig. 10 5 LEDs Efficiency vs. LED Current
VSHDN, 2V/div
0
5
10
15
20
LED Current (mA)
Fig. 11 3 LEDs Efficiency vs. LED Current
VOUT, 100mV/div
IINDUCTOR, 100mA/div
VOUT, 2V/div
IINDUCTOR, 100mA/div
VSW , 10V/div
VIN=3.6V; 3 LEDs; L1=10µF; COUT=0.22µF; ILED=20mA
Fig. 12
Start-Up from Shutdown
VIN=3.6V; 3 LEDs; L1=10µF; COUT=0.22µF; ILED=10mA
Fig. 13
Operation Wave Form
5
AIC1648
TYPICAL PERFORMANCE CHARACTERISTICS
(Continued)
25
11.0
10.0
9.5
9.0
3 LEDs
ILED=20mA
8.5
8.0
15
VIN=4.2V
10 V =3.6V
IN
VIN=3.3V
5
6 Samples' Temperature Data
7.5
7.0
20
LED Current (mA)
Output Voltage (V)
10.5
-40
-20
0
20
40
60
80
Temperature (°C)
Fig. 14 Output voltage vs. temperature
VIN=2.5V
4 LEDs
0
-80
100
-60
-40
-20
0
20
40
60
80
Temperature (°C)
Fig. 15 LED Current vs. Temperature
100
BLOCK DIAGRAM
Over Voltage
Comparator
27V
SHDN
PWM/PFM
Control
+
-
OVP
SW
VIN
Control
Logic
95mV
VREF
M1
Driver
+
*
-
+
FB
PWM
Comparator
Error
AMP
-
RC*
Slope
Compensation
1.2MHz
Oscillator
CC
+
*
Internal
Soft Start
Current AMP.
-
RS*
GND
6
AIC1648
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 to obtain LED current
according to the formula:
PIN 4: SHDN - Shutdown pin. Tie to higher than
1.5V to enable device, 0.3V or
less to disable device.
PIN 5: OVP
- Overvoltage protection. When
VOUT is greater than 27V, the
internal MOSFET turns off.
PIN 6: VIN
- Power input pin. Bypass VIN to
GND with a capacitor sitting as
close to VIN as possible.
RFB = 95mV/ILED
APPLICATION INFORMATION
Inductor Selection
A 10µH inductor is recommended for most
AIC1648 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).
Capacitor Selection
The small size of ceramic capacitors makes them
ideal for AIC1648 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 AIC1648
applications.
Diode Selection
Schottky diodes, with their low forward voltage
drop and fast reverse recovery, are the ideal
choices for AIC1648 applications. The forward
voltage drop of an 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 AIC1648. An Schottky
diode rated at 100mA to 200mA is sufficient for
most AIC1648 applications.
LED Current Control
LED current is controlled by feedback resistor
(RFB in Figure 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
Open-Circuit Protection
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. AIC1648 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. Connect builtin OVP (Over Voltage Protection) pin to output
terminal to prevent the damage resulting from an
open circuit condition.
7
AIC1648
cycle will decrease its brightness. In this
application, LEDs are dimmed by FB pin and
turned off completely by SHDN .
Dimming Control
There are three different ways of dimming control
circuits as follows:
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 18. With a VDC
ranging from 0V to 5V, the selection of resistors in
Figure 18 results in dimming control of LED
current from 20mA to 0mA, respectively.
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 AIC1648 are shown in Figure 16
and Figure 17. One, as Figure 16, uses PWM
signal to drive SHDN pin directly for dimming
control. The other, as Figure 17, 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
D1
L
VIN
C1
1µF
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 19.
10µH
VIN
SW
C2
RB521S-30
1µF
SHDN OVP
PWM
GND
FB
AIC1648
RFB
4.7Ω
Fig. 16 Dimming Control with a PWM Signal
D1
L
VIN
C1
1µF
10µH
VIN
SW
C2
1µF
RB521S-30
SHDN OVP
GND
FB
AIC1648
PWM
R2
R1
51K
1K
RFB
4.7Ω
Fig. 17 Dimming Control Using a PWM Signal
8
AIC1648
D1
L
VIN
C1
1µF
10µH
VIN
C2
1µF
RB521S-30
SW
SHDN OVP
GND
FB
AIC1648
VDC
0~5V
R2
R1
51K
1K
RFB
4.7Ω
Fig. 18 Dimming Control Using a DC Voltage
D1
L
VIN
C1
1µF
10µH
C2
1µF
RB521S-30
VIN
SW
SHDN OVP
GND
FB
AIC1648
R1
PWM
R3
5.1K
1K
R2
51K
RFB
4.7Ω
C3
0.1µF
Fig. 19 Dimming Control Using a Filter PWM Signal
APPLICATION EXAMPLE
D1
L
3.0~4.2V
C1
1µF
10µH
VIN
SW
C2
1µF
RB521S-30
SHDN OVP
20mA
GND
FB
AIC1648
RFB
4.7Ω
R1
4.7Ω
Fig. 20 Six White LEDs Application in Li-Ion Battery
9
AIC1648
PHYSICAL DIMENSIONS (unit: mm)
SOT-23-6
D
S
Y
M
B
O
L
A
A
e
e1
SEE VIEW B
b
WITH PLATING
c
A
A2
MIN.
MAX.
0.95
1.45
A1
0.05
0.15
A2
0.90
1.30
b
0.30
0.50
c
0.08
0.22
D
2.80
3.00
E
2.60
3.00
E1
1.50
1.70
E
E1
A
SOT-26
MILLIMETERS
0.95 BSC
1.90 BSC
L
θ
0.60
0.30
L1
0.60 REF
0°
8°
0.25
A1
BASE METAL
SECTION A-A
e
e1
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.
10
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