AAP2584 [ETC]
White LED Step-Up Converter In Tiny SOT-23 Package; 白光LED升压型转换器采用微型SOT- 23封装
| 型号： | AAP2584 |
| 厂家： | 
ETC |
| 描述： | White LED Step-Up Converter In Tiny SOT-23 Package |
| 文件： | 总11页 (文件大小：368K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
芯美 子
AAP2584
White LED Step-Up Converter
In Tiny SOT-23 Package
FEATURES
DESCRIPTION
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2.6V to 5.5V Input Range
The AAP2584 is a constant current step-up converter
specifically designed to drive white LEDs. The Step-up
converter topology allows series connection of the
white LEDs so the LED currents are identical for
uniform brightness. The AAP2584 switches at 1.1MHz,
allowing the use of tiny external components. The
input and output capacitor can be as small as 1µF,
saving space and cost versus alternative solutions. A
low 0.25V feedback voltage minimizes power loss in
the current setting resistor for better efficiency.
AAP2584 is enhanced with Soft-Start function and that
could significantly reduce noise induced by capacitor.
27V Output with Over Voltage Protection
High Efficiency :85 % Typical
Internal Soft-Start
PWM Dimming Control
Internal High Power 30V MOSFET Switch
Fast 1.1MHz Switching Frequency
Small, Low-Profile Inductors and Capacitors
SOT23-6 Package
RoHS Compliant and 100% Lead (Pb)-Free
The AAP2584 is available in low profile SOT23-6
package.
APPLICATIONS
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Mobile Phone
Digital Still Camera
PDAs, Handheld Computers
MP3 Players
GPS Receivers
Typical Application Circuit
Figure 1. White LED Application
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Pin Configurations
AAP2584
Package Type
Pin Configurations
SOT23-6
Pin Description
PIN
LX
SOT23-6
DESCRIPTION
1
2
Switch Pin. Connect inductor/diode here. Minimize trace area at this pin to reduce EMI.
Common Ground
GND
Feedback Pin. Reference voltage is 0.25V. Connect cathode of lowest LED and resistor
here. Calculate resistor value according to the formula: RFB=0.25/ILED
Chip Enable Pin. Connect to 1.4V or higher to enable device, 0.3V or less to disable
device.
FB
3
EN
IN
4
6
Input Supply Voltage
Overvoltage Sense. When VOUT is greater than 27V, the internal N-channel MOSFET turns
off until VOUT drops below 25V, then the IC reenters start. Connect a 1uF capacitor from
OUT to GND.
OUT
5
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Ordering Information
AAP2584
Order Number
Package Type
Marking
Operating Temperature range
q0 □ □ □ □
AAP2584VIR1
SOT23-6
-40 °C to 85°C
AAP2584 □ □ □ □
Lead Free Code
1: Lead Free 0: Lead
Packing
R: Tape & Reel
Operating temperature range
I: Industry Standard
Package Type
V: SOT23
Block Diagram
Figure 2.
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Absolute Maximum Ratings
AAP2584
Supply Voltage ,VIN ----------------------------------------------------------------- -0.3V to 6V
LX,OUT ----------------------------------------------------------------------------- -0.3V to 30V
The Other Pins ---------------------------------------------------------------------- -0.3V to 6V
Power dissipation, PD@ TA=25°C
SOT23-6 ------------------------------------------------------------------------------- 0.4W
Package Thermal Resistance
SOT23-6,θJA ------------------------------------------------------------------------- 250°C/W
Maximum Junction Temperature --------------------------------------------------- 125°C
Lead Temperature (Soldering, 10sec.) --------------------------------------------- 260°C
Storage Temperature Range --------------------------------------------------------- -65°C to 150°C
Operating Conditions
Junction Temperature Range ------------------------------------------------------- -40°C to 125°C
Supply Voltage , VIN----------------------------------------------------------------- 2.6V to 5.5V
Electrical Characteristics
(VIN =3.6V, VOUT=18V, COUT=1µF, CIN=1µF, RSENSE=12Ω,TA=-40°C to 85°C. Unless otherwise noted.
Typical values are at TA= 25°C)
AAP2584
Symbol
Parameter
Conditions
Unit
V
Min
--
Typ
--
Max.
6
Supply Voltage
VIN Rising
2.2
1.95
--
2.4
2.15
--
2.6
2.35
30
UVLO Under Voltage Lock Out
V
VIN Falling
No Switching
Maximum Output Voltage
V
ICC1
ICC2
Supply Current
VCC=6V, Continuous Switching
VCC=6V, FB=1.3V, No Switching
VCC=6V, VEN<0.3V
--
0.8
115
0.1
1.3
150
1
mA
µA
µA
Quiescent Current
Shutdown current
--
ICC3
--
Oscillator
Fosc
Operation Frequency
0.8
89
1.1
92
1.3
96
MHz
%
Dmax Maximum Duty Cycle
Reference Voltage
VFB
Feedback Voltage
230
250
270
mV
MOSFET
Ω
Rds (on) On resistance of MOSFET
ILX Current Limit
Control and Protection
--
1
1.5
1.2
0.4
0.8
A
VEN1
VEN2
IEN
Shutdown Voltage
0.3
--
0.7
0.7
--
V
V
Enable Voltage
1.4
EN Pin Pull Low Current
--
--
0.1
µA
Falling
Rising
24.5
26.1
25.7
27.3
26.5
28.1
OVP
OVP Threshold
V
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AAP2584
Typical Operating Characteristics
Efficiency vs. VIN (Driving 3WLEDs)
Efficiency vs. Vin (Driving 1WLED)
90%
88%
86%
84%
82%
80%
85%
IO=15mA
IO = 20m A
IO = 15m A
84%
IO=20mA
83%
82%
81%
80%
2
3
4
5
6
2
2.5
3
3.5
Vin(V)
Vin (V)
VIN=2.6V Driving 2LEDs Stability
Efficiency vs. VIN (Driving 6WLEDs)
84%
82%
80%
78%
76%
74%
IO=20mA
IO=15mA
2
3
4
5
6
Vin(V)
VIN=5V Driving 2LEDs Stability
VIN=3.6V Driving 2LEDs Stability
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AAP2584
VIN=2.6V Driving 4LEDs Stability
VIN=3.6V Driving 4LEDs Stability
VIN=5V Driving 4LEDs Stability
VIN=2.6V Driving 6LEDs Stability
VIN=5V Driving 6LEDs Stability
VIN=3.6V Driving 6LEDs Stability
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AAP2584
VIN=3.6V Driving 2LEDs Inrush Current
VIN=3.6V Driving 4LEDs Inrush Current
VIN=3.6V Driving 6LEDs 100Hz PWM Dimming
VIN=3.6V Driving 6LEDs Inrush Current
VIN=3.6V Driving 6LEDs 10KHz PWM Dimming
VIN=3.6V Driving 6LEDs 1KHz PWM Dimming
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AAP2584
VIN=3.6V Driving 6LEDs 100KHz PWM Dimming
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AAP2584
Application Information
b. Using a DC Voltage
Using a variable DC voltage to adjust the brightness is
a popular method in some applications. The dimming
control using a DC voltage circuit is shown in Figure 4.
According to the Superposition Theorem, as the DC
voltage increases, the voltage contributed to VFB
increases and the voltage drop on R2 decreases, i.e. the
LED current decreases. For example, if the VDC range
is from 0V to 2.8V, the selection of resistors in Figure 4
sets dimming control of LED current from 20mA to
0mA.
LED Current Control
The AAP2584 regulates the LED current by setting the
current sense resistor (R2) connecting to feedback and
ground. The internal feedback reference voltage is 0.25V.
The LED current can be set from following equation
easily.
0.25V
R2 =
--------------------------------------(1)
I
LED
In order to have an accurate LED current, precision
resistors are preferred (1% is recommended). The table
for R2 selection is shown below.
R2 Resistor Value selection
R2 (Ω)
50
I
LED (mA)
5
10
12
15
20
25
21
16.7
12.5
Inductor Selection
Figure 4. Dimming Control Using a DC Voltage
The recommended value of inductor for 2 to 6 WLEDs
applications are 4.7 to 22µH. Small size and better
efficiency are the major concerns for portable device,
such as AAP2584 used for mobile phone. The inductor
should have low core loss at 1.1MHz and low DCR for
better efficiency. To avoid inductor saturation current
rating should be considered.
c. Using a Filtered PWM signal
Another common application is using a filtered PWM
signal as an adjustable DC voltage for LED dimming
control. A filtered PWM signal acts as the DC voltage
to regulate the output current. The recommended
application circuit is shown in the Figure 6. In this
circuit, the output ripple depends on the frequency of
PWM signal. For smaller output voltage ripple
(<100mV), the recommended frequency of 2.8V PWM
signal should be above 2kHz. To fix the frequency of
PWM signal and change the duty cycle of PWM signal
can get different output current. According to the
application circuit of Figure 5, output current is from
20.5mA to 5.5mA by adjusting the PWM duty cycle
from 10% to 90%.
Dimming Control
a. Using a PWM Signal to EN Pin
For controlling the LED brightness, the AAP2584 can
perform the dimming control by applying a PWM
signal to EN pin. The internal soft-start and wide range
dimming frequency from 100Hz to 100KHz can
insignificantly reduce audio noise when dimming. The
average LED current is proportional to the PWM signal
duty cycle. The magnitude of the PWM signal should
be higher than the maximum enable voltage of EN pin,
in order to let the dimming control perform correctly.
Figure 5. Filtered PWM Signal for LED Dimming
Control
Figure 3. PWM Dimming Control Using the EN Pin
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AAP2584
Constant Output Voltage for Backlight of Main
Panel and Flashlight
Constant Output Voltage for Backlight of Main
Panel and Keypad
Figure 6 is an application of AAP2584 for backlight of
main panel and flashlight. Setting the divider-resistors
(R1 & R2) is to get a constant output voltage that
depends on the forward voltage and the numbers of
series-LEDs. There are three kinds of mode controlled
by the switches - backlight mode /flashlight mode
/backlight + flashlight mode. It can turn on backlight or
flashlight at one time or both at the same time.
Applying different duty cycle of PWM signal above
22kHz to backlight's switch can also control the
brightness. The following formula (2)(3) can determine
R3 and R4.
Figure 7 is another application of AAP2584 for
backlight and keypad. Setting the divider-resistors (R1
& R2) is to get a constant output voltage that depends
on the forward voltage and the numbers of series-LEDs.
It can turn on backlight of main panel and keypad at
the same time. Applying different duty cycle of PWM
signal above 22kHz to the backlight's switch can also
control the brightness of main panel's backlight. The
keypad's backlight will keep the same brightness
during the dimming control of main panel. Otherwise
the brightness of keypad's s backlight can also change
during the dimming control of main panel by using the
application circuit as figure 4. The following formula
(5)(6) can determine the resistors of Figure 8.
V
− 3VFb − V
OUT
DS
R3 =
R4 =
--------------------------(2)
--------------------------(3)
Ib
V
− 3VFb − V
OUT
DS
V
− 3VFf − V
R3 =
----------------------------(5)
OUT
DS
Ib
If
V
−3VFk
V
= Ib×R
---------------------------------(4)
DS(ON)
OUT
DS
R4 = R5 = R6 =
= Ib×R
----------------------(6)
Ik
----------------------------------(7)
DS(ON)
V
DS
Figure 6. Constant Output Voltage for Backlight and Flashlight
Figure 7. Constant Output Voltage for Backlight and Keypad
DS2584 Ver1.0 Mar. 2008
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AAP2584
Packaging Information
SOT23-6
MILLIMETERS
INCHES
SYMBOLS
MIN.
-
MAX.
1.45
0.15
0.50
MIN.
-
MAX.
A
A1
b
0.057
0.006
0.020
0.00
0.30
0.000
0.012
D
E1
e
2.90
1.60
0.95
0.114
0.063
0.037
E
L
2.60
0.3
3.00
0.60
0.102
0.012
0.118
0.024
DS2584 Ver1.0 Mar. 2008
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