Data Sheet WHITE LED STEP-UP CONVERTER General Description
The AP3029 is an inductor-based DC/DC converter designed to drive up to six white LEDs in series or 2 rows of LEDs with 5 for each in parallel for backlight. Only one feedback resistor is needed to control the LED current and obtain required brightness. A constant frequency 1.2MHz PWM control scheme is employed in this IC, which means tiny external components can be used. In fact, 1mm tall inductor and 0.22µF output capacitor for a typical application is sufficient. Additionally, the schottky diode in boost circuit is integrated on this chip. AP3029 also provides a disable pin to ease its use for different systems. The over output voltage protection is equipped in AP3029. When any LED is broken or in other abnormal conditions, the output voltage will be clamped. The AP3029 is available in standard SOT-23-6 and TSOT-23-6 packages.
AP3029 Features
· · · · · · · Inherently Uniform LED Current High Efficiency up to 83.5% No Need for External Schottky Diode Over Output Voltage Protection Fast 1.2MHz Switching Frequency Uses Tiny 1mm Tall Inductor Requires Only 0.22µF Output Capacitor
Applications
· · · · · Cellular Phones Digital Cameras LCD modules GPS Receivers PDAs, Handheld Computers
SOT-23-6
TSOT-23-6
Figure 1. Package Types of AP3029
Oct. 2009 Rev. 1. 8 1
BCD Semiconductor Manufacturing Limited
Data Sheet WHITE LED STEP-UP CONVERTER Pin Configuration
K/KT Package (SOT-23-6/TSOT-23-6)
Pin 1 Dot by Marking
AP3029
SW GND FB
1 2 3
6 5 4
VIN VOUT CTRL
Figure 2. Pin Configuration of AP3029 (Top View)
Pin Description
Pin Number 1 2 3 4 5 6 Pin Name SW GND FB CTRL VOUT VIN Switch Pin. Connect external inductor Ground Pin Voltage Feedback. Reference voltage is 200mV Shutdown and Dimming Pin. Connect to 1.8V or higher to enable device; Connect to 50mV or less to disable device; Connect to a voltage between 1.8V and 50mV to achieve linear dimming Output Pin. Connected to the cathode of internal schottky diode Input Supply Pin. Must be locally bypassed Function
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BCD Semiconductor Manufacturing Limited
Data Sheet WHITE LED STEP-UP CONVERTER Functional Block Diagram
FB
3
SOFT START
AP3029
SW
1 5 OVP
Q1
VOUT
VIN
6
VREF 1.25 V
200 mV
A1 A2
COMPARATOR
DRIVER R S Q
Σ
2
CTRL
4
RAMP GENERATOR
GND
1.2 MHz OSCILLATOR
Figure 3. Functional Block Diagram of AP3029
Ordering Information
AP3029 Circuit Type Package K: SOT-23-6 KT: TSOT-23-6
Package
SOT-23-6 TSOT-23-6
E1: RoHS TR: Tape and Reel
Temperature Range
-40 to 85 C -40 to 85 C
o o
Part Number
AP3029KTR-E1 AP3029KTTR-E1
Marking ID E8S S9F
Packing Type Tape & Reel Tape & Reel
BCD Semiconductor's products as designated with "E1" suffix in the part number are RoHS compliant.
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Data Sheet WHITE LED STEP-UP CONVERTER Absolute Maximum Ratings (Note 1)
Parameter Input Voltage SW Voltage FB Voltage CTRL Voltage Thermal Resistance (Junction to Atmosphere, no Heat sink) Operating Junction Temperature Storage Temperature Range Lead Temperature (Soldering, 10sec) ESD (Machine Model) ESD (Human Body Model) TSTG TLEAD θJA Symbol VIN Value 20 38 20 20 265 150 -65 to 150 260 250 2000 Unit V V V V
oC/W oC o o
AP3029
C C
V V
Note 1: Stresses greater than those listed under "Absolute Maximum Ratings" may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated under "Recommended Operating Conditions" is not implied. Exposure to "Absolute Maximum Ratings" for extended periods may affect device reliability.
Recommended Operating Conditions
Parameter Operating Temperature Range Input Voltage CTRL Voltage Symbol TOP VIN VCTRL Min -40 2.5 Max 85 16 16 Unit
o
C
V V
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Data Sheet WHITE LED STEP-UP CONVERTER Electrical Characteristics
(VIN=3V, VCTRL =3V, TA=25oC, unless otherwise specified.)
Parameter Minimum Operating Voltage Maximum Operating Voltage Feedback Voltage FB Pin Bias Current Supply Current Shutdown Quiescent Current Switching Frequency Maximum Duty Cycle Switch Current Limit (Note 2) Switch VCE Saturation Voltage Switch Leakage Current CTRL Pin Voltage VCTRL Symbol VIN(min) VIN(max) VFB IFB ICC IQ f DMAX ILIMIT VCESAT TA=25oC, D=40% TA=25oC, D=80% ISW=250mA VSW=5V High Low 40 CTRL Pin Bias Current ICTRL TA=85oC TA=-40oC OVP Voltage Schottky Forward Drop Schottky Leakage Current Soft Start Time Thermal Resistance (Junction to Case) t θJC SOT-23-6 TSOT-23-6 VOV VDROP ID=150mA Reverse Voltage VR=23V Reverse Voltage VR=27V 300 60 60 55 50 75 29 0.7 0.1 4 150 µS
oC/W
AP3029
Conditions
Min 2.5
Typ
Max
Unit V
16 IOUT=20mA, 4 LEDs, TA=-40oC to 85oC 188 200 35 VFB=VIN, No Switching VCTRL=0V 2.0 2.5 3.2 1.2 90 93 550 550 360 0.01 1.8 0.05 72 µA 5 mV µA V 212 100 3.2 5.0 mV nA mA µA MHz % mA
V V µA
Note 2: The Switch Current Limit is related to Duty Cycle. Please refer to Figure 15 for detail.
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BCD Semiconductor Manufacturing Limited
Data Sheet WHITE LED STEP-UP CONVERTER Typical Performance Characteristics
(VF of WLED is 3.45V @ IF=20mA, unless otherwise noted )
AP3029
85 84 83
85 84 83 82 81 80 79 78 77 2.5
Efficiency (%)
82 81 80 79 78 77 -50
VIN=3.6V, IOUT=20mA, 4 LEDs CIN=1µF, COUT=0.22µF, L=22µH
Efficiency (%)
IOUT=20mA, 4 LEDs, TA=25 C CIN=1µF, COUT=0.22µF, L=22µH
O
-25
0
25
50
o
75
100
3.0
3.5
4.0
4.5
5.0
Junction Temperature ( C)
Input Voltage (V)
Figure 4. Efficiency vs. Junction Temperature
Figure 5. Efficiency vs. Input Voltage
85 84 83
350
300
Schottky Forward Current (mA)
250
Efficiency (%)
82 81 80 79 78 77
200
150
VIN=3.6V, IOUT=20mA, TA=25 C CIN=1µF, COUT=0.22µF, L=22µH
O
100
50
0
2
3
4
5
6
0
200
400
600
800
1000
LEDs (PCS)
Schottky Forward Drop (mV)
Figure 6. Efficiency vs. LED's Number
Figure 7. Schottky Forward Current vs. Schottky Forward Drop
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BCD Semiconductor Manufacturing Limited
Data Sheet WHITE LED STEP-UP CONVERTER Typical Performance Characteristics (Continued)
(VF of WLED is 3.45V @ IF=20mA, unless otherwise noted )
AP3029
30
3.0
25
2.5
Quiescent Current (µA)
Supply Current (mA)
20
2.0
15
1.5
10
1.0
5 0.5 0
-50 C O 25 C O 100 C
0 2 4 6 8 10 12 14 16
O
2
4
6
8
10
12
14
16
0.0
Input Voltage (V)
Input Voltage (V)
Figure 8. Shutdown Quiescent Current vs. Input Voltage
Figure 9. Supply Current vs. Input Voltage
4.0 3.8 3.6
1.40 1.35 1.30 1.25
Input Current (mA)
Frequency (MHz)
3.0 3.5 4.0 4.5 5.0
3.4 3.2 3.0 2.8 2.6 2.4 2.2 2.0 2.5
1.20 1.15 1.10 1.05 1.00 0.95 0.90 -50
-25
0
25
50
o
75
100
Input Voltage (V)
Junction Temperature ( C)
Figure 10. Input Current in Output Open Circuit vs. Input Voltage
Figure 11. Switching Frequency vs. Junction Temperature
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BCD Semiconductor Manufacturing Limited
Data Sheet WHITE LED STEP-UP CONVERTER Typical Performance Characteristics (Continued)
(VF of WLED is 3.45V @ IF=20mA, unless otherwise noted )
AP3029
210 208
0.80 0.78 0.76
Schottky Forward Drop (V)
206
Feedback Voltage (mV)
204 202 200 198 196 194 192 190 -50 -25 0 25 50
o
0.74 0.72 0.70 0.68 0.66 0.64 0.62 0.60 -50
75
100
-25
0
25
50
o
75
100
Junction Temperature ( C)
Junction Temperature ( C)
Figure 12. Feedback Voltage vs. Junction Temperature
Figure 13. Schottky Forward Drop vs. Junction Temperature
0.50 0.45 0.40
700
Schottky Leakage Current (µA)
VR=10V VR=16V VR=23V
Current Limit (mA)
600
0.35 0.30 0.25 0.20 0.15 0.10 0.05 0.00 -50 -25 0 25 50
o
500
400
300
200
-50 C O 25 C O 100 C
40 50 60 70 80 90
O
75
100
100 30
Junction Temperature ( C)
Duty Cycle (%)
Figure 14. Schottky Leakage Current vs. Junction Temperature
Figure 15. Switch Current Limit vs. Duty Cycle
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BCD Semiconductor Manufacturing Limited
Data Sheet WHITE LED STEP-UP CONVERTER Typical Performance Characteristics (Continued)
(VF of WLED is 3.45V @ IF=20mA, unless otherwise noted )
AP3029
450 400 350 300 250 200 150 100 50 50
250
Feedback Voltage VFB (mV)
100 150 200 250 300
200
Saturation Voltage (mV)
150
100
50
0 0.0
0.5
1.0
1.5
2.0
2.5
Switch Current (mA)
CTRL Voltage (V)
Figure 16. Switch Saturation Voltage vs. Switch Current
Figure 17. Feedback Voltage vs. CTRL Pin Voltage
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Data Sheet WHITE LED STEP-UP CONVERTER Application Information
Operation
The AP3029 is a boost DC-DC converter which uses a constant frequency, current mode control scheme to provide excellent line and load regulation. Operation can be best understood by referring to the Figure 3. At the start of each oscillator cycle, the SR latch is set and switch Q1 turns on. The switch current will increase linearly. The voltage on sense resistor is proportional to the switch current. The output of the current sense amplifier is added to a stabilizing ramp and the result is fed into the non-inversion input of the PWM comparator A2. When this voltage exceeds the output voltage level of the error amplifier A1, the SR latch is reset and the switch is turned off. It is clear that the voltage level at inversion input of A2 sets the peak current level to keep the output in regulation. This voltage level is the output signal of error amplifier A1, and is the amplified signal of the voltage difference between feedback voltage and reference voltage of 200mV. So, a constant output current can be provided by this operation mode.
VIN ≥ 3V
L1
AP3029
R1 = 200mV I LED
Over Voltage Protection
The AP3029 has an internal open-circuit protection circuit. When the LEDs are disconnected from circuit or fail open, the output voltage is clamped. The AP3029 will switch at a low frequency, and minimize input current.
Soft Start
The AP3029 has an internal soft start circuit to limit the inrush current during startup. The time of startup is controlled by internal soft start capacitor. Please refer to Figure 19.
IIN 100mA/div VOUT 5V/div
VFB 100mV/div
VCTRL 2V/div Time 100µs/div
VIN
Control Signal
SW
VOUT
AP3029
CTRL GND FB
C2
Figure 19. Soft Start Waveform VIN=3.6V, 5 LEDs, ILED=20mA
C1
R1
Dimming Control
Figure 18. Typical Application circuit to Decide R1
LED Current Control
Refer to Figure 18, the LED current is controlled by the feedback resistor R1. LEDs' current accuracy is determined by the regulator's feedback threshold accuracy and is independent of the LED's forward voltage variation. So the precise resistors are preferred. The resistance of R1 is in inverse proportion to the LED current since the feedback reference is fixed at 200mV. The relation for R1 and LED current can be expressed as below: Oct. 2009 Rev. 1. 8 10
Two typical types of dimming control circuit are present as below. First, controlling CTRL Pin voltage to change operation state is a good choice. Second, changing the feedback voltage to get appropriate duty and luminous intensity is also useful. (1). Adding a Control Signal to CTRL Pin There are three methods to control CTRL pin signal First, adding a PWM Signal to CTRL pin directly. The AP3029 is turned on or off by the PWM signal when it is applied on the CTRL pin. The typical frequency of BCD Semiconductor Manufacturing Limited
Data Sheet WHITE LED STEP-UP CONVERTER Application Information (Continued)
this PWM signal can be up to 2KHz. Please refer to Figure 20.
AP3029
First, adding a constant DC voltage through a resistor divider to FB pin can control the dimming. Changing the DC voltage or resistor between the FB Pin and the DC voltage can get appropriate luminous intensity. Comparing with all kinds of PWM signal control, this method features a stable output voltage and LEDs current. Please refer Figure 23.
AP3029
CTRL
up to 2kHz
Figure 20. Dimming Control Using a PWM Signal in CTRL Pin
Secondly, adding a constant DC voltage through a resistor divider to CTRL pin can control the dimming. The FB voltage is indirectly adjusted when the CTRL pin voltage is between 50mV to 1.8V, which can be used as dimming control. Please refer Figure 21.
AP3029
FB VDC
R3 90K R2 5K R1 10Ω
Effective Feedback Voltage
Figure 23. Dimming Control Using DC Voltage
VDC R1 10k R2 10k
AP3029
CTRL
0.1 to 3.6 V
Second, using a filtered PWM signal can do it. The filtered PWM signal can be considered as a varying and adjustable DC voltage.
Figure 21. Dimming Control Using a DC Voltage in CTRL Pin
Thirdly, using a filtered PWM signal adding to CTRL pin can achieve dimming control. The filtered PWM signal can be considered as an adjustable DC voltage. It will change the FB voltage indirectly and achieve dimming control. The circuit is shown in Figure 22.
AP3029
FB PWM
R4 10K C R3 90K 0.1µF R2 5K R1 10Ω
Effective Feedback Voltage
PWM Signal
R1 5k C1 100nF
AP3029
CTRL
Figure 24. Dimming Control Using a Filtered PWM Voltage
Figure 22. Dimming Control Using a Filtered PWM Signal Voltage in CTRL Pin
Third, using a logic signal to change the feedback voltage. For example, the FB pin is connected to the GND through a mosFET and a resistor. And this mosFET is controlled a logic signal. The luminous intensity of LEDs will be changed when the mosFET turns on or off.
(2). Changing the Effective Feedback Voltage There are three methods to change the effective feedback voltage. Oct. 2009 Rev. 1. 8 11 BCD Semiconductor Manufacturing Limited
Data Sheet WHITE LED STEP-UP CONVERTER Application Information (Continued) AP3029
AP3029
FB Logic Signal R2 2N7002 R1 Effective Feedback Voltage
Figure 25. Dimming Control Using Logic Signal
Typical Application
VIN ≥ 3V
10µΗ
VIN Control Signal 1µ F CTRL
SW
VOUT 0.22µF FB 10Ω
AP3029
GND
C: X5R or X7R Dielectric L: SUMIDA CDRH5D28R-100NC or Equivalent This circuit can work in full temperature
A. Four White LEDs Driver
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BCD Semiconductor Manufacturing Limited
Data Sheet WHITE LED STEP-UP CONVERTER Typical Application (Continued)
VIN ≥ 3V
22µΗ
AP3029
Control Signal 1µF
VIN CTRL
SW
VOUT 0.22µF FB 10Ω
AP3029
GND
C: X5R or X7R Dielectric L: SUMIDA CDRH5D28R-220NC or Equivalent This circuit can work in full temperature
B. Six White LEDs Driver
VIN ≥ 3V
22µΗ
Control Signal 1µF
VIN CTRL
SW
VOUT 0.22µF FB 10Ω 10Ω
AP3029
GND
C: X5R or X7R Dielectric L: SUMIDA CDRH5D28R-220NC or Equivalent Two transistors are recommended to use Dual Matched transistor pairs This circuit can work in full temperature
C. Ten White LEDs Driver Figure 26. Typical Application of LED Drivers
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Data Sheet WHITE LED STEP-UP CONVERTER Mechanical Dimensions SOT-23-6 Unit: mm(inch) AP3029
2.820(0.111) 3.020(0.119) 0.300(0.012) 0.400(0.016)
0° 8° 0.200(0.008)
6
2.650(0.104) 2.950(0.116)
5
4
0.300(0.012) 0.600(0.024)
Pin 1 Dot by Marking
1
2
3
0.700(0.028)REF
0.950(0.037)TYP 1.800(0.071) 2.000(0.079)
1.500(0.059) 1.700(0.067)
0.000(0.000) 0.100(0.004)
0.100(0.004) 0.200(0.008)
0.900(0.035) 1.450(0.057) MAX 1.300(0.051)
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BCD Semiconductor Manufacturing Limited
Data Sheet WHITE LED STEP-UP CONVERTER Mechanical Dimensions TSOT-23-6 Unit: mm(inch) AP3029
2.800(0.110) 3.000(0.118)
R0.100(0.004) MIN
0° 8°
1.500(0.059) 1.700(0.067)
Pin 1 Dot by Marking
2.600(0.102) 3.000(0.118)
0.370(0.015) MIN
0.950(0.037) BSC 1.900(0.075) BSC GAUGE PLANE
0.100(0.004) 0.250(0.010)
0.250(0.010) BSC
0.700(0.028) 0.900(0.035)
1.000(0.039) MAX
0.000(0.000) 0.100(0.004)
0.350(0.014) 0.510(0.020)
Oct. 2009 Rev. 1. 8 15
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