AP5724

Pb
AP5724
WHITE LED STEP-UP CONVERTER
Description
Pin Assignments
The AP5724 is a step-up DC/DC converter specifically designed to
(Top View)
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
SW
1
6
VIN
GND
2
5
OVP
FB
3
74
EN
provides identical LED currents resulting in uniform brightness and
eliminates the need for ballast resistors. For driving higher number of
LEDs, AP5724 also supports a single feedback of parallel connected
multiple strings of equal number of LEDs.
The AP5724 switches at 1.2MHz that allows the use of tiny external
components. A low 0.1V feedback voltage minimizes power loss in
SOT26 / TSOT23-6
the current setting resistor for better efficiency
(Top View)
Features
•
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, TSOT26 and U-DFN2020-6: Available in “Green”
6
GND
VIN
2
5
FB
OVP
3
4
EN
Applications
Lead-Free Finish; RoHS Compliant (Notes 1 & 2) Notes:
1
U-DFN2020-6
Molding Compound (No Br, Sb)
•
SW
•
Cellular Phones
•
PDAs, Hand held Computers
•
Digital Cameras
•
MP3 Players
•
GPS Receivers
1. EU Directive 2002/95/EC (RoHS) & 2011/65/EU (RoHS 2) compliant. All applicable RoHS exemptions applied.
2. See http://www.diodes.com/quality/lead_free.html for more information about Diodes Incorporated’s definitions of Halogen- and Antimony-free, "Green"
and Lead-free.
Typical Applications Circuit
L1
22uH
VIN
D1
COUT
1uF
C IN
1uF
V IN
ON OFF
PWM Dimming
SW
AP5724 OVP
EN
FB
GND
2~6 LEDs
RSET
5
Figure 1 Typical Application Circuit
AP5724
Document number: DS31843 Rev. 4 - 2
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AP5724
Pin Descriptions
Pin Name
SW
GND
FB
Functions
Switch Pin. Connect inductor/diode here. Minimize trace area at this pin to reduce EMI.
GND pin.
Feedback Pin. Reference voltage is 0.1V. Connect cathode of lowest LED and a sense resister here. Calculate resistor value
according to the formula: RSET = 0.1V / 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.
EN
OVP
VIN
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
-
A1
CONTROL
LOGIC
OTP
+
Cc
FB 3
+
VREF
0.1V
Σ
-
VIN 6
RAMP
Generator
2 GND
Enable
EN 4
1.2MHz
Oscillator
Absolute Maximum Ratings (@TA = +25°C, unless otherwise specified.)
Symbol
Parameter
Rating
Unit
V
VIN Pin Voltage
-0.3 to +7
VSW
SW Voltage
-0.3 to +34
V
VOVP
OVP Pin Voltage
-0.3 to +35
V
VFB
Feedback Pin Voltage
-0.3 to +7
V
EN
EN
-0.3 to +7
V
150
°C
VIN
TJ(MAX)
Maximum Junction Temperature
TLEAD
Lead Temperature
TST
Caution:
Storage Temperature Range
300
°C
-65 to +150
°C
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.
AP5724
Document number: DS31843 Rev. 4 - 2
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AP5724
Recommended Operating Conditions (@TA = +25°C, unless otherwise specified.)
Symbol
VIN
Input Voltage
Parameter
Min
2.7
Max
5.5
Unit
V
TJ
Operating Junction Temperature
-40
125
°C
TA
Operating Ambient Temperature
-40
85
°C
Electrical Characteristics (@ VIN = 3.6V, TA = +25°C, unless otherwise specified.)
Symbol
System Supply Input
Parameter
Conditions
Min
Typ
Max
Unit
V
VIN
Operating Input Voltage
2.7
—
5.5
UVLO
Under Voltage Lockout
—
2.2
2.4
V
Under Voltage Lockout Hysteretic
—
85
—
mV
IQ
Quiescent Current
FB = 0.2V, No Switching
—
500
—
μA
ISD
Shutdown Current
VEN < 0.4V
—
0.1
1
μA
Operation Frequency
1
1.2
1.4
MHz
Dmax
Maximum Duty Cycle
Reference Voltage
86
90
—
%
0.09
0.1
0.11
V
10
45
100
nA
Oscillator
FOSC
VFB
Feedback Voltage
IFB
FB Pin Bias Current
MOSFET
Rds(on)
IOCP
On Resistance of MOSFET
Switching Current Limit
—
0.95
1.2
Ω
Normal Operation
—
750
—
mA
ON
OFF
1.5
—
—
—
—
0.4
V
V
SOT26 (Note 3)
Control and Protection
EN
EN
Voltage High
Voltage Low
IEN
EN Pin Pull Low Current
—
4
6
μA
OVP Threshold
26
—
30
162
34
—
V
—
—
—
—
—
152
200
36
32
30
—
—
—
—
—
°C/W
OVP
θJA
θJC
Note:
Thermal Resistance Junction-to-Ambient TSOT26 (Note 3)
U-DFN2020-6 (Note 3)
SOT26 (Note 3)
TSOT26 (Note 3)
Thermal Resistance Junction-to-Case
U-DFN2020-6 (Note 3)
°C/W
3. Test condition for SOT26, TSOT26 and U-DFN2020-6: Device mounted on FR-4 substrate, single-layer PC board, 2oz copper, with minimum
recommended pad layout
AP5724
Document number: DS31843 Rev. 4 - 2
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AP5724
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
600
500
400
300
200
100
0
2.5
3
3.5
4
4.5
5
0
5.5
2.5
VIN (V)
3
4.5
5
5.5
100
1.2
95
Max Duty(%)
Frequency(MHz)
4
VIN (V)
VIN vs. Max Duty
VIN vs. Frequency
1.25
1.15
1.1
90
85
1.05
1
80
2.5
3
3.5
4
VIN (V)
4.5
5
5.5
2.5
3
VIN vs. Feedback Voltage
3.5
4
VIN(V)
4.5
5
5.5
IOUT vs. Feedback Voltage
0.12
0.12
0.11
0.11
Feedback Voltage(V)
Feedback Voltage(V)
3.5
0.1
0.09
0.08
0.07
0.1
0.09
0.08
0.07
0.06
0.06
2.5
3
3.5
AP5724
Document number: DS31843 Rev. 4 - 2
4
VIN (V)
4.5
5
5.5
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0
10
20
30
IOUT (mA)
40
50
December 2013
© Diodes Incorporated
AP5724
Typical Performance Characteristics (cont.) (6 LEDS, VIN = 3.6V, IOUT = 25mA)
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
V IN = 3.6V
1.1
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(mV)
120
VIN = 4.2V
110
100
VIN = 3.6V
90
80
70
60
-50
-25
0
25
50
75
Temperature (℃)
AP5724
Document number: DS31843 Rev. 4 - 2
100
125
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AP5724
Typical Performance Characteristics (cont.) (6 LEDS, VIN = 3.6V, IOUT = 25mA)
IOUT vs. Efficiency
IOUT vs. Efficiency
90
90
V IN = 4.2V
Efficiency(%)
85
85
75
Efficiency(%)
80
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
AP5724
Document number: DS31843 Rev. 4 - 2
VIN (V)
4
4.5
5
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AP5724
Typical Performance Characteristics (cont.) (6 LEDS, VIN = 3.6V, IOUT = 25mA)
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
AP5724
Document number: DS31843 Rev. 4 - 2
VEN
VEN
VOUT
VOUT
Irushi
Irushin
g
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AP5724
Applications Information
Inductor Selection
A 10μH to 22μH inductor is recommended for most AP5724 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 the ceramic capacitors are ideal for AP5724 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 AP5724 applications. For high output current applications like 3S8P, larger output capacitor of 2.2µF to 4.7µF 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 AP5724 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 AP5724. 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 AP5724. A Schottky diode rated at 100mA to
200mA is sufficient for most AP5724 applications.
LED Current Control
The LED current is controlled by the feedback resistor (RSET in Figure 1). The feedback reference is 0.1V. The LED current is 0.1V/ 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 = 0.1V/ILED (See Table 1)
Table 1. RSET Resistor Value Selection
ILED (mA)
RSET (Ω)
5
10
15
20
30
40
20
10
6.6
5
3.3
2.5
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 AP5724
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
AP5724 OVP
EN
FB
GND
x
x
RSET
5
Figure 2 LED Driver with Open-Circuit Protection
AP5724
Document number: DS31843 Rev. 4 - 2
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AP5724
Applications Information (cont.)
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 AP5724 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 AP5724 and corresponds to
zero LED current. A 100% duty cycle corresponds to full current. The typical frequency range of the PWM signal is below 2 kHz.
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.
AP5724
FB
VDC
R3
100k
R2
5k
RSET
5
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.
AP5724
FB
RINC
Logic
Signal
RSET
Figure 4 Dimming Control Using a Logic Signal
AP5724
Document number: DS31843 Rev. 4 - 2
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AP5724
Applications Information (cont.)
VOUT
VIN
C1
1uF
D2
D1
L1
B0540WS
LED
LED
C2
1uF
U1
1
D3
22uH
2
R1
5ohm
3
SW
GND
Vin
OVP
FB
EN
6
5
4
AP5724
ON
OFF
D4
LED
D5
LED
D6
LED
D7
LED
Table 2. Suggested Inductors
Vendor
Wurth Electronics
GOTREND
TAIYO YUDRN
Inductors
(µH)
22
22
22
Table 3. Suggested Capacitors for CIN and COUT
Vendor
Capacitance
TAIYO YUDEN
1µF
Current Rating
(A)
0.51A
0.56A
0.51A
Type
SMD
SMD
SMD
Dimensions
(mm)
3.8X 3.8 X 1.6
3.8 X 3.8 X 1.05
4.0 X 4.0 X 1.25
Type
SMD
Series
TMK212 B7105MG-T
Rating
40V/0.5A
40V/0.5A
40V/0.25A
Type
SOD323
SOD323
SOD523
Series
ZLLS400
B0540WS
SDM20U40
Table 5. Suggested Resistor
Vendor
YAGEO
Type
SMD
Series
FR-SK
Table 6. Suggested W-LED
Vendor
LITEON
Type
SMD
Series
LTW-C1911UC5
Table 4. Suggested Diodes
Vendor
ZETEX
DIODES
DIODES
AP5724
Document number: DS31843 Rev. 4 - 2
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Series
744031220
GLP3810PH220N
NR4012
December 2013
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AP5724
Ordering Information
AP 5724 XXX G - 7
Package
Green
W : SOT26
WU : TSOT26
FDC : U-DFN2020-6
G : Green
Part Number
Package Code
Packaging
AP5724WG-7
AP5724WUG-7
AP5724FDCG-7
W
WU
FDC
SOT26
TSOT26
U-DFN2020-6
Packing
7 : Tape & Reel
7” Tape and Reel
Quantity
3000/Tape & Reel
3000/Tape & Reel
3000/Tape & Reel
Part Number Suffix
-7
-7
-7
Marking Information
(1)
SOT26 and TSOT26
( Top View )
5
4
7
6
XX Y W X
1
2
3
Part Number
AP5724WG-7
AP5724WUG-7
(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
SOT26
TSOT26
Identification Code
FB
GB
U-DFN2020-6
( Top View )
XX
YWX
Part Number
AP5724FDCG-7
AP5724
Document number: DS31843 Rev. 4 - 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
U-DFN2020-6
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Identification Code
GB
December 2013
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AP5724
Package Outline Dimensions (All dimensions in mm.)
Please see AP02002 at http://www.diodes.com/datasheets/ap02002.pdf for latest version.
(1) SOT26
A
SOT26
Dim Min Max Typ
A
0.35 0.50 0.38
B
1.50 1.70 1.60
C
2.70 3.00 2.80
D
⎯
⎯ 0.95
H
2.90 3.10 3.00
J
0.013 0.10 0.05
K
1.00 1.30 1.10
L
0.35 0.55 0.40
M
0.10 0.20 0.15
0°
8°
α
⎯
All Dimensions in mm
B C
H
K
M
J
L
D
(2) TSOT26
D
e1
E
E1
L2
c
4x θ1
e
L
θ
6x b
A
A2
A1
TSOT26
Dim Min Max Typ
A
1.00
−
−
A1 0.01 0.10
−
A2 0.84 0.90
−
D
2.90
−
−
E
2.80
−
−
1.60
E1
−
−
b
0.30 0.45
−
c
0.12 0.20
−
e
0.95
−
−
1.90
e1
−
−
L
0.30 0.50
L2
0.25
−
−
θ
0°
8°
4°
θ1
4°
12°
−
All Dimensions in mm
(3) U-DFN2020-6 Type C
A
A3
A1
Seating Plane
D
D2
Pin #1 ID
E
E2
Z (4x)
L
e
AP5724
Document number: DS31843 Rev. 4 - 2
U-DFN2020-6
Type C
Dim Min Max Typ
A
0.57 0.63 0.60
A1
0.00 0.05 0.02
0.15
A3
––
––
b
0.25 0.35 0.30
D
1.95 2.075 2.00
D2
1.55 1.75 1.65
E
1.95 2.075 2.00
E2
0.86 1.06 0.96
0.65
e
––
––
L
0.25 0.35 0.30
––
––
Z
0.20
All Dimensions in mm
b
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AP5724
Suggested Pad Layout
Please see AP02001 at http://www.diodes.com/datasheets/ap02001.pdf for the latest version.
(1) SOT26
C2
Z
C2
Dimensions Value (in mm)
Z
3.20
G
1.60
X
0.55
Y
0.80
C1
G
C1
C2
Y
2.40
0.95
X
(2) TSOT26
C
C
Dimensions Value (in mm)
C
0.950
X
0.700
Y
1.000
Y1
3.199
Y1
Y (6x)
X (6x)
(3) U-DFN2020-6 Type C
X2
X1
Dimensions
Y (6x)
Y2
C
X
X1
X2
Y
Y1
Y2
Y1
X (6x)
AP5724
Document number: DS31843 Rev. 4 - 2
Value
(in mm)
0.650
0.350
1.650
1.700
0.525
1.010
2.400
C
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AP5724
Tape Orientation
For U-DFN2020-6
Note:
4. The taping orientation of the other package type can be found on our website at http://www.diodes.com/datasheets/ap02007.pdf.
AP5724
Document number: DS31843 Rev. 4 - 2
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AP5724
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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
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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 systems, and
acknowledge and agree that they are solely responsible for all legal, regulatory and safety-related requirements 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 © 2013, Diodes Incorporated
www.diodes.com
AP5724
Document number: DS31843 Rev. 4 - 2
15 of 15
www.diodes.com
December 2013
© Diodes Incorporated
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