ACTIVE-SEMI ACT6311UC-T

ACT6311
Rev 3, 22-Feb-11
White LED/OLED Step-Up Converter
FEATURES
GENERAL DESCRIPTION
•
•
•
•
•
•
The ACT6311 step-up DC/DC converter is
optimized for driving OLEDs or white LEDs. It can
provide an output voltage up to 24V. The device is
capable of driving up to seven LEDs in series from a
Lithium-Ion battery, with inherent current matching
and uniform brightness.
Adjustable Output Voltage
Drives OLEDs or White LEDs
30V High Voltage Switch
1MHz Switching Frequency
Tiny Inductors and Capacitors
The ACT6311 incorporates a 30V high voltage
switch. The device operates at 1MHz and allows the
use of few external components. The ACT6311 is
available in the tiny SOT23-5 package.
Tiny SOT23-5 Package
APPLICATIONS
•
•
•
•
•
•
OLED Applications
Cell Phones
Digital Cameras
PDAs, Laptops
MP3 Players
GPS
Efficiency vs. Output Current
ACT6311-0001
100
Efficiency (%)
80
60
VIN = 3.6V
VIN = 3V
VIN = 3V
VIN = 3.6V
40
20
0
0
5
10
15
20
25
30
35
Output Current (mA)
Figure 1. Typical Application Circuit
Innovative PowerTM
-1-
www.active-semi.com
Copyright © 2011 Active-Semi, Inc.
ACT6311
Rev 3, 22-Feb-11
G
Figure 2: Application as White LED Drive
ORDERING INFORMATION
PART NUMBER
TEMPERATURE RANGE
PACKAGE
PINS
TOP MARK
PACKING
ACT6311UC-T
-40°C to 85°C
SOT23-5
5
YCXB
TAPE & REEL
PIN CONFIGURATION
SW
1
G
2
FB
3
5
IN
4
SHDN
ACT6311
UC
SOT23-5
PIN DESCRIPTION
PIN NUMBER
PIN NAME
PIN DESCRIPTION
1
SW
Switch Output. Connect this pin to the inductor and the Schottky diode. To reduce
EMI, minimize the PCB trace path between this pin and the input bypass capacitor.
2
G
Ground.
3
FB
Feedback Input. This pin is referenced to 1.24V
4
SHDN
5
IN
Innovative PowerTM
Shutdown Control. Connect to a logic high to enable the device. Connect to a
logic low to disable the device. Never leave the pin unconnected.
Supply Input. Bypass to G with a capacitor 1µF capacitor or higher.
-2-
www.active-semi.com
Copyright © 2011 Active-Semi, Inc.
ACT6311
Rev 3, 22-Feb-11
ABSOLUTE MAXIMUM RATINGS
(Note: Exceeding these limits may damage the device. Exposure to absolute maximum rating conditions for long periods may affect
device reliability.)
PARAMETER
VALUE
UNIT
IN, SHDN Voltage
-0.3 to 6
V
SW Voltage
-0.3 to 30
V
FB Voltage
-0.3 to VIN + 0.3
V
Maximum Power Dissipation (derate 5mW/°C above TA = 50°C)
0.4
W
Junction to Ambient Thermal Resistance (θJA)
190
°C/W
-40 to 150
°C
300
°C
Operating Junction Temperature
Lead Temperature (Soldering, 10 sec)
ELECTRICAL CHARACTERISTICS
(VIN = VSHDN = 3V, TA = 25°C, unless otherwise specified.)
PARAMETER
SYMBOL
TEST CONDITIONS
Input Voltage Range
Feedback Voltage
MIN
TYP
2.5
VFB
VIN = 3V
1.18
FB Input Current
1.24
MAX UNIT
5.5
V
1.30
V
50
nA
Supply Current
SHDN = IN
0.7
1.5
mA
Supply Current in Shutdown
SHDN = G
0
1
µA
1.2
MHz
Switching Frequency
fSW
0.8
1
Maximum Duty Cycle
DMAX
80
85
%
Switch Current Limit
ILIM
75% Duty Cycle
320
mA
Switch On Voltage
ISW = 200mA
350
mV
Switch Leakage Current
VSW = 20V, SHDN = G
SHDN Logic High Threshold
10
1.6
V
SHDN Logic Low Threshold
SHDN Input Current
Innovative PowerTM
0
-3-
µA
0.4
V
1
µA
www.active-semi.com
Copyright © 2011 Active-Semi, Inc.
ACT6311
Rev 3, 22-Feb-11
ERROR
AMPLIFIER
Figure 3. Functional Block Diagram
with the output of the error amplifier. If the error
comparator output is high, the flip-flop is reset and
the power switch turns off. Thus, the peak inductor
current level is controlled by the error amplifier
output, which is integrated from the difference
between FB input and the 1.24V reference point.
FUNCTIONAL DESCRIPTION
The ACT6311 is a high efficiency step-up DC/DC
converter that employs a current-mode, fixed
frequency pulse-width modulation (PWM)
architecture with excellent line and load regulation.
Figure 3 shows the functional block diagram of the
IC. The flip-flop is set at the start of each oscillator
cycle, and turns on the power switch. During this on
time, the switch current level is sensed and added
to a ramp signal, and the resulting sum is compared
Innovative PowerTM
The ACT6311 operates at a constant switching
frequency for output current higher than 4mA. If the
output current decreases further, the IC will enter
frequency modulation mode, resulting in some low
frequency ripple.
-4-
www.active-semi.com
Copyright © 2011 Active-Semi, Inc.
ACT6311
Rev 3, 22-Feb-11
APPLICATION INFORMATION
and determine R2 from the output voltage:
Inductor Selection
⎛ V
⎞
R 2 = R 1 ⎜ OUT − 1 ⎟
⎝ 1 . 24 V
⎠
Table 1:
Recommended Inductors
PART NUMBER
(1)
White LED Application
CURRENT
DCR
RATING
(Ω)
(MA)
The LED current is determined by the value of the
feedback resistor R1. Because the FB input of the
IC is regulated to 1.24V, the LED current is
determined by ILED = 1.24V/R1. The value of R1 for
different LED currents is shown in Table 3.
SUPPLIER
CDRH3D16-220
350
0.5
Sumida
ELJPC220KF
160
4.0
Panasonic
LQH3C220
250
0.7
Murata
LEM2520-220
125
5.5
Taiyo Yuden
Table 3:
R1 Resistor Value Selection
ILED (MA)
R1 (Ω)
5
246
10
124
12
103.3
Capacitor Selection
15
82.7
The ACT6311 only requires a 1µF input capcitor
and a 1µF output capacitor for most applications.
Ceramic capacitors are ideal for these applications.
For best performance, use X5R and X7R type
ceramic capacitors, which possess less degradation
in capacitance over voltage and temperature
ranges.
20
62
A 22µH inductor is typically used for the ACT6311.
The inductor should have low DC resistance (DCR)
and losses at 1MHz. See Table 1 for examples of
small size inductors.
To improve efficiency, resistors R2 and R3 can be
connected as shown in Figure 4 to lower the
effective feedback voltage.
The following are dimming control methods for the
ACT6311 series white LED application.
Diode Selection
1) PWM Signal Driving SHDN
The ACT6311 requires a fast recovery Schottky
diode as the rectifier. Select a low forward voltage
drop Schottky diode with a forward current (IF)
rating of 100mA to 200mA and a sufficient peak
repetitive reverse voltage (VRRM). Some suitable
Schottkky diodes are listed in Table 2.
When a PWM signal is connected to the SHDN pin,
the ACT6311 is turned on and off alternately under
the control of the PWM signal. The current through
the LEDs is either zero or full scale. By changing
the duty cycle of the PWM signal (typically 1kHz to
10kHz), a controlled average current is obtained.
2) DC Voltage Control
Table 2:
Recommended Schottky Diodes
PART
NUMBER
IF(MA)
VRRM (V)
CMDSH-3
100
30
Central
CMDSH2-3
200
30
Central
BAT54
200
30
Zetex
Figure 5 shows an application in which a DC
voltage is used to adjust the LED current. The LED
current increases when VDC is lower than VFB and
decreases when VDC is higher than VFB. In Figure 5,
the LED current range of 15mA to 0mA is controlled
by VDC = 0V to 2V.
SUPPLIER
3) Filtered PWM Control
Figure 6 shows an application using a filtered PWM
signal to control dimming.
OLED Application
4) Logic Control
Figure 1 shows the feedback network necessary to
set the output voltage. Select the proper ratio of the
two feedback resistors R1 and R2 based on the
desired output voltage. Typically choose R1 = 20kΩ
Innovative PowerTM
A logic signal can be used to adjust the LED current
in a discrete step, as shown in Figure 7.
-5-
www.active-semi.com
Copyright © 2011 Active-Semi, Inc.
ACT6311
Rev 3, 22-Feb-11
LED1
ACT6311
FB
LED2
LED3
R2
R1
LOGIC
Figure 4. Current Setting for White LED Application
Figure 7. Logic Controlled Dimming
Start-up and Inrush Current
In order to facilitate quick startup, a soft-start circuit
is not incorporated into the ACT6311. When the IC
is first turned on with no external soft-start circuit,
the peak inrush current is about 400mA. Figure 8
shows an implementation for soft-start. When
soft-start and dimming controls are used
simultaneously, a low frequency PWM signal (less
than 10kHz) or the methods in Figures 5, 6 and 7
should be used.
LED1
LED2
ACT6311
FB
LED3
R3
R2
33.4k
56k
VDC
Open-Circuit Protection (White LEDs)
R1
62Ω
If one of the LEDs is disconnected, the FB voltage
drops to zero and the IC switches at maximum duty
cycle. This results in a high voltage that may
exceed the SW voltage rating. To limit this voltage,
use a Zener diode as shown in Figure 9. The Zener
voltage must be large than the total forward voltage
of the LEDs and the current rating should be higher
than 0.1mA.
Figure 5. DC Voltage Controlled Dimming
LED1
Board Layout
To reduce EMI, minimize the area and path length
of all traces connected to SW. Use a ground plane
under the switching regulator and connect R1
directly to the G pin of the IC.
LED2
ACT6311
FB
LED3
R4
R3
R2
10k
33.4k
C1
0.1µF
56k
PWM
R1
62Ω
Figure 6. Filtered PWM Controlled Dimming
Innovative PowerTM
-6-
www.active-semi.com
Copyright © 2011 Active-Semi, Inc.
ACT6311
Rev 3, 22-Feb-11
D1
OUTPUT
C1
100nF
R2
200k
ACT6311
FB
D2
R3
56k
R1
20k
Figure 9: Open-Circuit Protection
Figure 8: Soft-Start Circuit
Innovative PowerTM
-7-
www.active-semi.com
Copyright © 2011 Active-Semi, Inc.
ACT6311
Rev 3, 22-Feb-11
TYPICAL PERFORMANCE CHARACTERISTICS
(Circuit of Figure 1, unless otherwise specified.)
Efficiency vs. Output Voltage
70
60
VIN = 3.6V
Switching Frequency (MHz)
80
VIN = 3V
50
40
30
20
10
ACT6311-0002
90
Efficiency (%)
Switching Frequency vs. Temperature
1.10
ACT6311-0001
100
1.05
1.00
0.95
0.90
0
0
5
10
15
20
25
30
-40
35
-15
FB Voltage (V)
Current Limit (mA)
ACT6311-0004
1.25
250
300
VIN = 3V
1.20
1.15
1.10
40
50
60
70
80
-40
-15
Load Regulation
Output Voltage (V)
Output Voltage (V)
12.5
VIN = 3.6V
20
25
30
35
5.5
13.0
12.5
3.0
IOUT = 20mA
3.5
4.0
4.5
Input Voltage (V)
Load (mA)
Innovative PowerTM
5.0
13.5
12.0
15
85
ACT6311-0006
13.0
10
60
14.0
ACT6311-0005
13.5
5
35
Line Regulation
14.0
0
10
Temperature (°C)
Duty Cycle (%)
12.0
85
1.30
ACT6311-0003
400
30
60
FB Voltage vs. Temperature
Current Limit vs. Duty Cycle
450
20
35
Temperature (°C)
Output Current (mA)
250
10
-8-
www.active-semi.com
Copyright © 2011 Active-Semi, Inc.
ACT6311
Rev 3, 22-Feb-11
TYPICAL PERFORMANCE CHARACTERISTICS CONT’D
(Circuit of Figure 1, unless otherwise specified.)
Switching Waveform in Discontinuous Mode
Startup without Soft Start Circuit
Inductor
Current
200mA/DIV
Inductor
Current
100mA/DIV
VOUT
200mV/DIV
ACT6311-0008
ACT6311-0007
SW
5V/DIV
VOUT
5V/DIV
VIN = 3V
No load
VIN = 3.6V
ILOAD = 20MA
SHDN
1µs/DIV
20µs/DIV
Startup with Soft Start Circuit
Load Step Response
VOUT
1V/DIV
VOUT
5V/DIV
20mA
Load Step
2mA
VIN = 3.6V
ILOAD = 20mA
Test Circuit Figure 8
SHDN
ACT6311-0010
ACT6311-0009
Inductor
Current
50mA/DIV
VIN = 3.6V
VOUT = 13.6V
100µs/DIV
4ms/DIV
Line Step Response
ACT6311-0011
VOUT = 13.6V
IOUT = 10mA
VOUT
500mV/DIV
5.5V
VIN
3V
100µs/DIV
Innovative PowerTM
-9-
www.active-semi.com
Copyright © 2011 Active-Semi, Inc.
ACT6311
Rev 3, 22-Feb-11
PACKAGE OUTLINE
SOT23-5 PACKAGE OUTLINE AND DIMENSIONS
SYMBOL
DIMENSION IN
MILLIMETERS
DIMENSION IN
INCHES
MIN
MAX
MIN
MAX
A
-
1.450
-
0.057
A1
0.000
0.150
0.000
0.006
A2
0.900
1.300
0.035
0.051
b
0.300
0.500
0.012
0.020
c
0.080
0.220
0.003
0.009
D
2.900 BSC
0.114 BSC
E
1.600 BSC
0.063 BSC
E1
2.800 BSC
0.110 BSC
e
0.950 BSC
0.037 BSC
e1
1.900 BSC
0.075 BSC
L
0.60REF
0.024REF
L1
0.300
0.600
0.012
0.024
θ
0°
8°
0°
8°
Active-Semi, Inc. reserves the right to modify the circuitry or specifications without notice. Users should evaluate each
product to make sure that it is suitable for their applications. Active-Semi products are not intended or authorized for use
as critical components in life-support devices or systems. Active-Semi, Inc. does not assume any liability arising out of
the use of any product or circuit described in this datasheet, nor does it convey any patent license.
Active-Semi and its logo are trademarks of Active-Semi, Inc. For more information on this and other products, contact
sales@active-semi.com or visit http://www.active-semi.com.
®
is a registered trademark of Active-Semi.
Innovative PowerTM
- 10 -
www.active-semi.com
Copyright © 2011 Active-Semi, Inc.