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AP5725
WHITE LED STEP-UP CONVERTER
Description
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. 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.
Pin Assignments
(Top View)
SW 1 6 VIN
(Top View)
SW VIN
1 2 3 6 5 4
GND
2
5 7 4
OVP
GND FB EN
FB
3
EN
OVP
SOT26 / TSOT23-6
DFN2020C-6
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, TSOT23-6 and DFN2020C-6: Available in "Green" Molding Compound (No Br, Sb) Lead Free Finish/ RoHS Compliant (Note 1)
Applications
* * * * * Cellular Phones PDAs, Hand held Computers Digital Cameras MP3 Players GPS Receivers
Notes:
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 C IN 1uF V IN ON OFF PWM Dimming SW
2~6 LEDs
D1 COUT 1uF
VIN
AP5725 OVP EN FB GND
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 1F or 2.2F to reduce input noise.
Functional Block Diagram
OVP 5
1 SW Comparator Driver A2 Rc CONTROL LOGIC Q1
+
OTP
FB 3 VIN 6
A1
+
Cc
VREF 0.25V
RAMP Generator
2 GND EN 4 Enable 1.2MHz Oscillator
AP5725
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AP5725
WHITE LED STEP-UP CONVERTER Absolute Maximum Ratings
Symbol VIN VSW VOVP VFB EN TJ(MAX) TLEAD TST VIN Pin Voltage SW Voltage OVP Pin Voltage Feedback Pin Voltage EN Maximum Junction Temperature Lead Temperature Storage Temperature Range Parameter Rating -0.3~7 -0.3~34 -0.3~35 -0.3~7 -0.3~7 150 300 -65 to +150 Unit V V V V V
o o 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 Min 2.7 -40 -40 Max 5.5 125 85 Unit V o C o C
AP5725
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AP5725
WHITE LED STEP-UP CONVERTER Electrical Characteristics (VIN = 3.6V, TA = 25C, 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 JA JC
Notes:
Conditions
Min 2.7 1 86 0.225 10 1.5 26
Typ. 2.2 85 500 0.1 1.2 90 0.25 45 0.95 750 4 30 162 152 200 36 32 30
Max 5.5 2.4 1 1.4 0.275 100 1.2 0.4 6 34
Unit V V mV A A MHz % V nA mA V V A V
o
FB=0.35V, No Switching VEN < 0.4V
Normal Operation ON OFF
Thermal Resistance Junction-toAmbient Thermal Resistance Junction-toCase
SOT26 (Note 2) TSOT23-6 (Note 2) DFN2020C-6 (Note2) SOT26 (Note 2) TSOT23-6 (Note 2) DFN2020C-6 (Note 2)
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
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AP5725
WHITE LED STEP-UP CONVERTER Typical Performance Characteristics (6 LEDs ; VIN = 3.6V ; IOUT = 25mA)
VIN vs. Shutdown Current 1 Shutdown Current(uA)
Quiescent Current(uA) 700 600 500 400 300 200 100 0 2.5 3 3.5 4 VIN (V) 4.5 5 5.5 VIN vs. Quiescent Current
0.8 0.6 0.4 0.2 0 2.5 3 3.5 4 VIN (V) 4.5 5 5.5
VIN vs. Frequency 1.25 Frequency(MHz) 1.2 1.15 1.1 1.05 1 2.5 3 3.5 4 VIN (V) 4.5 5 5.5
Max Duty(%) 100 95 90 85 80 2.5 3
VIN vs. Max Duty
3.5
4 VIN(V)
4.5
5
5.5
VIN vs. Feedback Voltage
0.3
0.3
IOUT vs. Feedback Voltage
Feedback Voltage(V)
Feedback Voltage(V)
0.28 0.26 0.24 0.22 0.2 2.5 3 3.5 4 4.5 5 5.5
0.28 0.26 0.24 0.22 0.2 0 10 20 30 40 50
VIN (V)
I OUT (mA)
AP5725
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AP5725
WHITE LED STEP-UP CONVERTER Typical Performance Characteristics (Continued)
V IN vs. OVP Threshold 35 OVP Threshold(V) 33 31 29 27 25 2.5 3 3.5 4 V IN (V) 4.5 5 5.5
Shutdown Current(uA) 1 0.8 0.6 0.4 0.2 0 -50
Temperature vs. Shutdown Current
-25
0
25 50 75 Temperature ()
100
125
Temperature vs. OVP Threshold 35 OVP Threshold(V) 30 25 20 15 10 -50 -25 0 25 50 75 Temperature () 100 125
Tem perature vs. Frequency 1.7 V IN = 4.2V 1.4 Frequency (MHZ) 1.1 0.8 0.5 0.2 -50 -25 0 25 50 75 Tem perature () 100 125 V IN = 3.6V
Temperature vs. Feedback Voltage
0.28 0.27
Feedback Voltage(V)
VIN = 4.2V
0.26 0.25 0.24 0.23 -50 -25 0
VIN = 3.6V
Temperature( )
25
50
75
100
125
AP5725
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AP5725
WHITE LED STEP-UP CONVERTER Typical Performance Characteristics (Continued)
IOUT vs. Efficiency 90 85 Efficiency(%) 80 75 70 65 60 0 5 10 15 20 IOUT (m A) 25 30 V IN = 3.6V V IN = 4.2V
Efficiency(%) 90 85 80 75
IOUT vs. Efficiency
VIN = 4.2V
VIN = 3.6V 70 65
4 LEDs ; L = 22uH
6 LEDs ; L = 22uH
60 0 5 10 15 IOUT (mA) 20 25 30
VIN vs. Efficiency
100 90
Efficiency(%) 3 LEDs 4 LEDs
80 70 60 50 40 2.5 3 3.5
VIN (V) 6 LEDs
4
4.5
5
AP5725
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AP5725
WHITE LED STEP-UP CONVERTER Typical Performance Characteristics (Continued)
VOUT Ripple VIN = 3.6V; 4 LEDs ; IOUT = 30mA VOUT Ripple VIN = 3.6V; 6 LEDs ; IOUT = 30mA
SW
SW
VOUT
VOUT
POWER ON VIN = 3.6V; 6 LEDs ; IOUT = 30mA
POWER OFF VIN = 3.6V; 6 LEDs ; IOUT = 30mA
VEN
VEN
VOUT
VOUT
Irushi
Irushin g
AP5725
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AP5725
WHITE LED STEP-UP CONVERTER Applications Information
Inductor Selection A 10H~22H 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 1F input capacitor and a 1F 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 () 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.
VIN C IN 1uF
L1 22uH
D1 COUT 1uF
V IN
SW x x RSET 12 FB
AP5725 OVP EN 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 R3 100k R2 5k RSET
12
Figure 3. Dimming Control Using a DC Voltage
VDC
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 L1 C1 1uF D2 LED 1 2 D3 LED R1 12ohm 3 D1 B0540WS U1 SW GND FB AP5725 D4 LED Vin OVP EN 6 5 4 22uH C2 1uF VIN
ON
OFF
D5 LED
D6 LED
D7 LED
Table 2. Suggested Inductors Inductors Vendor (uH) Wurth Electronics GOTREND TAIYO YUDRN 22 22 22
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
Series 744031220 GLP3810PH220N NR4012
Table 3. Suggested Capacitors for CIN and COUT Vendor TAIYO YUDEN Capacitance 1uF Type SMD Series TMK212 B7105MG-T
Table 4. Suggested Diodes Vendor Rating ZETEX DIODES DIODES 40V/0.5A 40V/0.5A 40V/0.25A
Type SOD323 SOD323 SOD523
Series ZLLS400 B0540WS SDM20U40
Table 5. Suggested Resistor Vendor Type YAGEO SMD Table 6. Suggested W-LED Vendor Type LITEON SMD
Series FR-SK
Series LTW-C1911UC5
AP5725
Document number: DS31844 Rev. 3 - 2
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AP5725
WHITE LED STEP-UP CONVERTER Ordering Information
AP 5725 XXX G - 7 Package
W : SOT26 WU : TSOT23-6 FDC : DFN2020C-6
Device AP5725WG-7 AP5725WUG-7 AP5725FDCG-7
Notes:
Green
G : Green
Packing
7 : Tape & Reel
Package Code W WU FDC
Packaging (Note 3) SOT26 TSOT23-6 DFN2020C-6
7" Tape and Reel Quantity Part Number Suffix 3000/Tape & Reel -7 3000/Tape & Reel -7 3000/Tape & Reel -7
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 )
6 5 4
7
XX Y W X
1
Part Number AP5725WG-7 AP5725WUG-7 (2) DFN2020C-6
2
3
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
Identification Code FC GC
Package SOT26 TSOT23-6
( Top View )
XX YWX
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
Identification Code GC
Part Number AP5725FDCG-7
Package DFN2020C-6
AP5725
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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
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AP5725
WHITE LED STEP-UP CONVERTER Package Outline Dimensions (Continued)
(3) Package Type: DFN2020C-6
0.57/0.63 0.43mon. 0.15max.
Marking
0.10 C 0.08 C
(Active area depth) Seating plane
C
0/0.05
0.25 A
2x
Pin#1 ID B
Top View
0.37
1.95/2.075 1.55/1.75
A
R0. 15
1.95/2.075
0.86/1.06
0.25/0.35
1 R0.
0.45
2x-
0.25 B
0.65 0.25/0.35 1.59
0.10 M C A B
0.65nom.
Bottom View
Land Pattern Recommendation (Unit:mm)
AP5725
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AP5725
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
IMPORTANT NOTICE 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 PARTICULAR PURPOSE (AND THEIR EQUIVALENTS UNDER THE LAWS OF ANY JURISDICTION). Diodes Incorporated and its subsidiaries reserve the right to make modifications, enhancements, improvements, corrections or other changes without further notice to this document and any product described herein. Diodes Incorporated does not assume any liability arising out of the application or use of this document or any product described herein; neither does Diodes Incorporated convey any license under its patent or trademark rights, nor the rights of others. Any Customer or user of this document or products described herein in such applications shall assume all risks of such use and will agree to hold Diodes Incorporated and all the companies whose products are represented on Diodes Incorporated website, harmless against all damages. Diodes Incorporated does not warrant or accept any liability whatsoever in respect of any products purchased through unauthorized sales channel. Should Customers purchase or use Diodes Incorporated products for any unintended or unauthorized application, Customers shall indemnify and hold Diodes Incorporated and its representatives harmless against all claims, damages, expenses, and attorney fees arising out of, directly or indirectly, any claim of personal injury or death associated with such unintended or unauthorized application. Products described herein may be covered by one or more United States, international or foreign patents pending. Product names and markings noted herein may also be covered by one or more United States, international or foreign trademarks. 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 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 (c) 2010, Diodes Incorporated www.diodes.com
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