AP5725

AP5725
WHITE LED STEP-UP CONVERTER
Description
Pin Assignments
(Top View)
The AP5725 is a step-up DC/DC converter specifically
designed to drive white LEDs with a constant current. The
device can drive 2 ~ 6 LEDs in series from a Li-Ion cell.
Series connection of the LEDs provides identical LED
currents resulting in uniform brightness and eliminates the
need for ballast resistors. For driving higher number of LEDs,
AP5725 also supports a single feedback of parallel
connected multiple strings of equal number of LEDs.
SW
1
6
VIN
GND
2
5
OVP
3
74
FB
EN
(Top View)
SW
1
6
GND
VIN
2
5
FB
OVP
3
4
EN
SOT26 / TSOT23-6
The AP5725 switches at 1.2MHz that allows the use of tiny
external components. A low 0.25V feedback voltage
minimizes power loss in the current setting resistor for better
efficiency.
Features
Applications
•
•
•
•
•
•
•
•
•
•
•
•
•
High efficiency: 84% typical
Fast 1.2MHz switching frequency
Current limit and UVLO protections
Internal thermal shutdown
Internal Over Voltage Protection
Integrated soft-start function
SOT26, TSOT23-6 and DFN2020C-6: Available in
“Green” Molding Compound (No Br, Sb)
Lead Free Finish/ RoHS Compliant (Note 1)
Notes:
DFN2020C-6
Cellular Phones
PDAs, Hand held Computers
Digital Cameras
MP3 Players
GPS Receivers
1. EU Directive 2002/95/EC (RoHS). All applicable RoHS exemptions applied. Please visit our website at
http://www.diodes.com/products/lead_free.html.
Typical Application Circuit
L1
22uH
VIN
D1
COUT
1uF
C IN
1uF
V IN
ON OFF
PWM Dimming
SW
AP5725 OVP
EN
FB
GND
2~6 LEDs
RSET
12
Figure 1. Typical Application Circuit
AP5725
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AP5725
WHITE LED STEP-UP CONVERTER
Pin Descriptions
Pin Name
SW
GND
FB
EN
OVP
VIN
Description
Switch Pin. Connect inductor/diode here. Minimize trace area at this pin to reduce EMI.
GND pin.
Feedback Pin. Reference voltage is 0.25V. Connect cathode of lowest LED and a sense
resister here. Calculate resistor value according to the formula: RSET = 0.25V / ILED
Converter On/Off Control Input. A high input at EN turns the converter On, and a low input
turns it off. If On/Off control is not needed, connect EN to the input source for automatic
startup. The EN pin cannot be left floating.
Output Voltage detect pin for over voltage protection.
Input Supply Pin. Must be locally bypassed with 1μF or 2.2μF to reduce input noise.
Functional Block Diagram
OVP
5
1 SW
Comparator
-
Driver
Q1
A2
+
Rc
-
CONTROL
LOGIC
OTP
A1
+
Cc
VREF
0.25V
Σ
-
VIN 6
+
FB 3
RAMP
Generator
EN 4
2 GND
Enable
1.2MHz
Oscillator
AP5725
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AP5725
WHITE LED STEP-UP CONVERTER
Absolute Maximum Ratings
Symbol
Rating
Unit
VIN Pin Voltage
-0.3~7
V
VSW
SW Voltage
-0.3~34
V
VOVP
OVP Pin Voltage
-0.3~35
V
VFB
Feedback Pin Voltage
-0.3~7
V
EN
EN
-0.3~7
VIN
TJ(MAX)
TLEAD
TST
Parameter
150
300
o
-65 to +150
o
Maximum Junction Temperature
Lead Temperature
Storage Temperature Range
V
o
C
C
C
Caution: Operation above the absolute maximum ratings can cause device failure. These values, therefore, must not be exceeded under
any condition. Operation at the absolute maximum rating for extended periods, may reduce device reliability.
Recommended Operating Conditions
Symbol
VIN
TJ
TA
Parameter
Input Voltage
Operating Junction Temperature
Operating Ambient Temperature
AP5725
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Min
2.7
-40
-40
Max
5.5
125
85
Unit
V
o
C
o
C
July 2010
© Diodes Incorporated
AP5725
WHITE LED STEP-UP CONVERTER
Electrical Characteristics (VIN = 3.6V, TA = 25°C, unless otherwise specified.)
Symbol
Parameter
System Supply Input
VIN
Operating Input Voltage
UVLO
Under Voltage Lockout
Under Voltage Lockout Hysteretic
IQ
Quiescent Current
ISD
Shutdown Current
Oscillator
FOSC
Operation Frequency
Dmax
Maximum Duty Cycle
Reference Voltage
VFB
Feedback Voltage
IFB
FB Pin Bias Current
MOSFET
Rds(on) On Resistance of MOSFET
IOCP
Switching Current Limit
Control and Protection
EN
Voltage High
EN
Voltage Low
IEN
EN Pin Pull Low Current
OVP
OVP Threshold
θJA
Thermal Resistance Junction-toAmbient
θJC
Thermal Resistance Junction-toCase
Notes:
Conditions
FB=0.35V, No Switching
VEN < 0.4V
Normal Operation
ON
OFF
SOT26 (Note 2)
TSOT23-6 (Note 2)
DFN2020C-6 (Note2)
SOT26 (Note 2)
TSOT23-6 (Note 2)
DFN2020C-6 (Note 2)
Min
Typ.
Max
Unit
2.7
-
2.2
85
500
0.1
5.5
2.4
1
V
V
mV
μA
μA
1
86
1.2
90
1.4
-
MHz
%
0.225
10
0.25
45
0.275
100
V
nA
-
0.95
750
1.2
-
Ω
mA
1.5
26
4
30
162
152
200
36
32
30
0.4
6
34
V
V
μA
V
o
C/W
o
C/W
2. Test condition for SOT26, TSOT23-6 and DFN2020C-6: Device mounted on FR-4 substrate, single-layer PC board, 2oz copper,
with minimum recommended pad layout
AP5725
Document number: DS31844 Rev. 3 - 2
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AP5725
WHITE LED STEP-UP CONVERTER
Typical Performance Characteristics (6 LEDs ; VIN = 3.6V ; IOUT = 25mA)
VIN vs. Shutdown Current
VIN vs. Quiescent Current
700
Quiescent Current(uA)
Shutdown Current(uA)
1
0.8
0.6
0.4
0.2
0
2.5
3
3.5
4
4.5
5
600
500
400
300
200
100
0
5.5
2.5
VIN (V)
3
3.5
1.25
5
5.5
100
1.2
Max Duty(%)
Frequency(MHz)
4.5
VIN vs. Max Duty
VIN vs. Frequency
1.15
1.1
1.05
1
95
90
85
80
2.5
3
3.5
4
VIN (V)
4.5
5
5.5
2.5
3
3.5
4
VIN(V)
4.5
5
5.5
IOUT vs. Feedback Voltage
VIN vs. Feedback Voltage
0.3
Feedback Voltage(V)
0.3
Feedback Voltage(V)
4
VIN (V)
0.28
0.26
0.24
0.22
0.28
0.26
0.24
0.22
0.2
0.2
2.5
3
3.5
4
4.5
5
5.5
VIN (V)
AP5725
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0
10
20
30
40
50
I OUT (mA)
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© Diodes Incorporated
AP5725
WHITE LED STEP-UP CONVERTER
Typical Performance Characteristics (Continued)
Temperature vs. Shutdown Current
V IN vs. OVP Threshold
1
Shutdown Current(uA)
OVP Threshold(V)
35
33
31
29
27
0.8
0.6
0.4
0.2
25
0
2.5
3
3.5
4
V IN (V)
4.5
5
5.5
-50
-25
0
25
50
75
Temperature (℃)
100
125
Tem perature vs. Frequency
Temperature vs. OVP Threshold
35
1.7
30
1.4
Frequency (MHZ)
OVP Threshold(V)
V IN = 4.2V
25
20
15
10
1.1
V IN = 3.6V
0.8
0.5
0.2
-50
-25
0
25
50
75
Temperature (℃)
100
125
-50
-25
0
25
50
75
Tem perature (℃)
100
125
Temperature vs. Feedback Voltage
Feedback Voltage(V)
0.28
0.27
VIN = 4.2V
0.26
VIN = 3.6V
0.25
0.24
0.23
-50
-25
0
25
50
Temperature(℃ )
AP5725
Document number: DS31844 Rev. 3 - 2
75
100
125
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AP5725
WHITE LED STEP-UP CONVERTER
Typical Performance Characteristics (Continued)
IOUT vs. Efficiency
IOUT vs. Efficiency
90
90
V IN = 4.2V
85
80
75
Efficiency(%)
Efficiency(%)
85
V IN = 3.6V
70
65
VIN = 4.2V
80
75
VIN = 3.6V
70
65
4 LEDs ; L = 22uH
6 LEDs ; L = 22uH
60
60
0
5
10
15
20
IOUT (m A)
25
30
0
5
10
15
IOUT (mA)
20
25
30
VIN vs. Efficiency
100
3 LEDs
Efficiency(%)
90
4 LEDs
80
6 LEDs
70
60
50
40
2.5
3
3.5
4
4.5
5
VIN (V)
AP5725
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AP5725
WHITE LED STEP-UP CONVERTER
Typical Performance Characteristics (Continued)
VOUT Ripple
VIN = 3.6V; 6 LEDs ; IOUT = 30mA
VOUT Ripple
VIN = 3.6V; 4 LEDs ; IOUT = 30mA
SW
SW
VOUT
VOUT
POWER OFF
VIN = 3.6V; 6 LEDs ; IOUT = 30mA
POWER ON
VIN = 3.6V; 6 LEDs ; IOUT = 30mA
AP5725
Document number: DS31844 Rev. 3 - 2
VEN
VEN
VOUT
VOUT
Irushi
Irushin
g
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AP5725
WHITE LED STEP-UP CONVERTER
Applications Information
Inductor Selection
A 10μH~22μH inductor is recommended for most AP5725 applications. For high efficiency the inductor should
have low core losses at 1.2MHz and low DCR (copper wire resistance). The inductor saturation current rating
should also exceed the peak input current, especially for high load current applications (like 3S8P).
Capacitor Selection
The small size of ceramic capacitors are ideal for AP5725 applications. X5R and X7R types are recommended
because they retain their capacitance over wider voltage and temperature ranges than other types such as Y5V or
Z5U. A 1μF input capacitor and a 1μF output capacitor are sufficient for most AP5725 applications. For high
output current applications like 3S8P, larger output capacitor of 2.2uF ~ 4.7uF is recommended to minimize output
ripple.
Diode Selection
Schottky diodes, with their low forward voltage drop and fast reverse recovery, are the ideal choices for AP5725
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 the AP5725. Schottky diodes with higher current ratings usually have lower forward voltage
drop and larger diode capacitance. Larger Schottky diode capacitance can cause significant switching losses at
the 1.2MHz switching frequency of the AP5725. A Schottky diode rated at 100mA to 200mA is sufficient for most
AP5725 applications.
LED Current Control
The LED current is controlled by the feedback resistor (RSET in Figure 1). The feedback reference is 0.25V. The
LED current is 0.25V/ RSET. In order to have accurate LED current, precision resistors are preferred (1% is
recommended). The formula and table for RSET selection are shown below.
RSET = 0.25V/ILED (See Table 1)
Table 1. RSET Resistor Value Selection
ILED (mA)
RSET (Ω)
5
50
10
25
15
16.6
20
12.5
30
8.3
AP5725
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AP5725
WHITE LED STEP-UP CONVERTER
Applications Information (Continued)
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. The AP5725 will then switch at a high duty cycle resulting in a high output voltage, which may
cause the SW and OVP pin voltage to exceed the voltage rating of these pins. The OVP pin monitors the output
voltage. If the output voltage reaches the over voltage protection threshold at the OVP pin (Figure 2), the over
voltage protection is activated and SW pin stops switching.
L1
22uH
VIN
D1
COUT
1uF
C IN
1uF
V IN
SW
x
AP5725 OVP
EN
x
FB
RSET
12
GND
Figure 2. LED Driver with Open-Circuit Protection
Dimming Control
There are four different types of dimming control circuits:
1. Using a PWM Signal to EN Pin
With the PWM signal applied to the EN pin, the AP5725 is turned on or off by the PWM signal. The LEDs operate
at either zero or full current. The average LED current increases proportionally with the duty cycle of the PWM
signal. A 0% duty cycle will turn off the AP5725 and corresponds to zero LED current. A 100% duty cycle
corresponds to full current. The typical frequency range of the PWM signal is below 2kHz.
AP5725
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AP5725
WHITE LED STEP-UP CONVERTER
Applications Information (Continued)
2. Using a DC Voltage
For some applications, the preferred method of brightness control is a variable DC voltage to adjust the
LED current. The dimming control using a DC voltage is shown in Figure 3. As the DC voltage increases, the
voltage drop on R2 increases and the voltage drop on RSET decreases. Thus, the LED current decreases. The
selection of R2 and R3 will make the current from the variable DC source much smaller than the LED current and
much larger than the FB pin bias current. For VDC range from 0V to 2V, the selection of resistors in Figure 3 gives
dimming control of LED current from 0mA to 20mA.
AP5725
FB
VDC
R3
100k
R2
5k
RSET
12
Figure 3. Dimming Control Using a DC Voltage
3. Using a Filtered PWM Signal
The 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.
4. Using a Logic Signal
For applications that need to adjust the LED current in discrete steps, a logic signal can be used as shown in
Figure 4. RSET sets the minimum LED current (when the NMOS is off). RSET sets how much the LED current
increases when the NMOS is turned on.
AP5725
FB
RINC
Logic
Signal
RSET
Figure 4. Dimming Control Using a Logic Signal
AP5725
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AP5725
WHITE LED STEP-UP CONVERTER
Applications Information (Continued)
VOUT
VIN
L1
C1
1uF
D2
D1
22uH
B0540WS
LED
C2
1uF
U1
1
2
D3
R1
12ohm
LED
3
Vin
SW
GND
OVP
FB
EN
6
5
4
ON
OFF
AP5725
D4
LED
D5
LED
D6
LED
D7
LED
Table 2. Suggested Inductors
Inductors
Vendor
(uH)
Current Rating
(A)
Type
Dimensions
(mm)
Series
Wurth Electronics
22
0.51A
SMD
3.8X 3.8 X 1.6
744031220
GOTREND
22
0.56A
SMD
3.8 X 3.8 X 1.05
GLP3810PH220N
TAIYO YUDRN
22
0.51A
SMD
4.0 X 4.0 X 1.25
NR4012
Table 3. Suggested Capacitors for CIN and COUT
Vendor
Capacitance
Type
Series
TAIYO YUDEN
1uF
SMD
TMK212 B7105MG-T
Type
Series
Table 4. Suggested Diodes
Vendor
Rating
ZETEX
40V/0.5A
SOD323
ZLLS400
DIODES
40V/0.5A
SOD323
B0540WS
DIODES
40V/0.25A
SOD523
SDM20U40
Table 5. Suggested Resistor
Vendor
Type
YAGEO
SMD
Series
FR-SK
Table 6. Suggested W-LED
Vendor
Type
LITEON
SMD
Series
LTW-C1911UC5
AP5725
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AP5725
WHITE LED STEP-UP CONVERTER
Ordering Information
AP 5725 XXX G - 7
Device
AP5725WG-7
AP5725WUG-7
AP5725FDCG-7
Notes:
Package
Green
W : SOT26
WU : TSOT23-6
FDC : DFN2020C-6
G : Green
Package
Code
W
WU
FDC
Packing
7 : Tape & Reel
7” Tape and Reel
Quantity
Part Number Suffix
3000/Tape & Reel
-7
3000/Tape & Reel
-7
3000/Tape & Reel
-7
Packaging
(Note 3)
SOT26
TSOT23-6
DFN2020C-6
3. Pad layout as shown on Diodes Inc. suggested pad layout document AP02001, which can be found on our website at
http://www.diodes.com/datasheets/ap02001.pdf.
Marking Information
(1) SOT26 and TSOT23-6
( Top View )
5
4
7
6
XX Y W X
1
2
3
Part Number
AP5725WG-7
AP5725WUG-7
XX : Identification Code
Y : Year 0~9
W : Week : A~Z : 1~26 week;
a~z : 27~52 week; z represents
52 and 53 week
X : A~Z : Green
Package
SOT26
TSOT23-6
Identification Code
FC
GC
(2) DFN2020C-6
( Top View )
XX
YWX
Part Number
AP5725FDCG-7
AP5725
Document number: DS31844 Rev. 3 - 2
XX : Identification Code
Y : Year : 0~9
W : Week : A~Z : 1~26 week;
a~z : 27~52 week; z represents
52 and 53 week
X : A~Z : Green
Package
DFN2020C-6
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Identification Code
GC
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AP5725
WHITE LED STEP-UP CONVERTER
Package Outline Dimensions (All Dimensions in mm)
(1) Package Type: SOT26
(2) Package Type: TSOT23-6
AP5725
Document number: DS31844 Rev. 3 - 2
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WHITE LED STEP-UP CONVERTER
Package Outline Dimensions (Continued)
0.43mon.
0.57/0.63
(3) Package Type: DFN2020C-6
Marking
0.15max.
0.10 C
0.25 A
Pin#1 ID
2x
0/0.05
0.08 C
B
1.95/2.075
1.55/1.75
(Active area depth)
Seating plane
C
Top View
0.37
A
2x-
0.9
0.45
0.25/0.35
0.86/1.06
1.95/2.075
R0.
15
1
R0.
0.65
0.25 B
0.65nom.
0.25/0.35
Bottom View
AP5725
Document number: DS31844 Rev. 3 - 2
1.59
0.10 M C A B
Land Pattern Recommendation
(Unit:mm)
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WHITE LED STEP-UP CONVERTER
Taping Orientation
For DFN2020C-6
Notes:
4. The taping orientation of the other package type can be found on our website at http://www.diodes.com/datasheets/ap02007.pdf.
AP5725
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AP5725
WHITE LED STEP-UP CONVERTER
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DIODES INCORPORATED MAKES NO WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, WITH REGARDS TO THIS
DOCUMENT, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
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LIFE SUPPORT
Diodes Incorporated products are specifically not authorized for use as critical components in life support devices or systems without
the express written approval of the Chief Executive Officer of Diodes Incorporated. As used herein:
A. Life support devices or systems are devices or systems which:
1. are intended to implant into the body, or
2. 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 significant injury to the user.
B.
A critical component is any component in a life support device or system whose failure to perform can be reasonably expected
to cause the failure of the life support device or to affect its safety or effectiveness.
Customers represent that they have all necessary expertise in the safety and regulatory ramifications of their life support devices or
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concerning their products and any use of Diodes Incorporated products in such safety-critical, life support devices or systems,
notwithstanding any devices- or systems-related information or support that may be provided by Diodes Incorporated. Further,
Customers must fully indemnify Diodes Incorporated and its representatives against any damages arising out of the use of Diodes
Incorporated products in such safety-critical, life support devices or systems.
Copyright © 2010, Diodes Incorporated
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AP5725
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