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Preliminary Datasheet 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 0.22F 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 to 27V. 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 Drives 2 to 6 LEDs in Series or 2 Rows of LEDs with 5 for Each in Parallel Fast 1.2MHz Switching Frequency Uses Tiny 1mm Tall Inductor Requires Only 0.22F Output Capacitor
Applications
* * * * * Cellular Phones Digital Cameras LCD modules GPS Receivers PDAs, Handheld Computers
SOT-23-6
TSOT-23-6
Figure 1. Package Type of AP3029
Aug. 2008 Rev. 1. 2 1
BCD Semiconductor Manufacturing Limited
Preliminary Datasheet 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
Aug. 2008 Rev. 1. 2 2
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Preliminary Datasheet WHITE LED STEP-UP CONVERTER Functional Block Diagram
FB
3
SOFT START
AP3029
SW
1 5
VOUT
VIN
6
VREF 1.25 V
200 mV
A1 A2
COMPARATOR R S Q
DRIVER
Q1
OVP
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
Part Number Lead Free
AP3029KTR-E1 AP3029KTTR-E1
E1: Lead Free G1: Green TR: Tape and Reel
Package
SOT-23-6 TSOT-23-6
Temperature Range
-40 to 85oC -40 to 85 C
o
Marking ID Lead Free E8S S9F G8S L9F Green
Green
AP3029KTR-G1 AP3029KTTR-G1
Packing Type Tape & Reel Tape & Reel
BCD Semiconductor's Pb-free products, as designated with "E1" suffix in the part number, are RoHS compliant. Products with "G1" suffix are available in green packages.
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Preliminary Datasheet 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 RJA Symbol VIN Value 20 27 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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Preliminary Datasheet 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 Schottky Forward Drop Schottky Leakage Current Soft Start Time t VDROP ID=150mA Reverse Voltage VR=23V Reverse Voltage VR=27V 300 55 50 75 0.7 0.1 4 150 S V A 1.8 0.05 72 A VFB=VIN, No Switching VCTRL=0V 1.5 2.0 0.9 90 IOUT=20mA, 4 LEDs, TA=-40oC to 85oC 188 200 35 2.5 3.2 1.2 93 550 550 360 0.01 5 mV A V Conditions Min 2.5 V 16 212 100 3.2 5.0 1.5 mV nA mA A MHz % mA Typ Max Unit
AP3029
Note 2: The Switch Current Limit is related to Duty Cycle. Please refer to Figure 16 for detail.
Aug. 2008 Rev. 1. 2 5
BCD Semiconductor Manufacturing Limited
Preliminary Datasheet 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=1F, COUT=0.22F, L=22H
Efficiency (%)
IOUT=20mA, 4 LEDs, TA=25 C CIN=1F, COUT=0.22F, L=22H
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 2 3 4 5 6
200
150
100
VIN=3.6V, IOUT=20mA, TA=25 C CIN=1F, COUT=0.22F, L=22H
O
50
0 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
Aug. 2008 Rev. 1. 2 6
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Preliminary Datasheet 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 (A)
20
Supply Current (mA)
2.0
15
1.5
10
1.0
5 0.5 0 2 4 6 8 10 12 14 16 0.0 0 2 4 6 8 10 12
-50 C O 25 C O 100 C
14 16
O
Input Voltage (V)
Input Voltage (V)
Figure 8. Shutdown Quiescent Current vs. Input Voltage
Figure 9. Supply Current vs. Input Voltage
29.0 4.0 28.5 3.8 3.6 3.4 27.5 27.0 26.5 26.0 25.5 25.0 2 4 6 8 10 12 14 16
Output Clamp Voltage (V)
28.0
Input Current (mA)
3.2 3.0 2.8 2.6 2.4 2.2 2.0 2.5
3.0
3.5
4.0
4.5
5.0
Input Voltage (V)
Input Voltage (V)
Figure 10. Output Clamp Voltage vs. Input Voltage
Figure 11. Input Current in Output Open Circuit vs. Input Voltage
Aug. 2008 Rev. 1. 2 7
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Preliminary Datasheet WHITE LED STEP-UP CONVERTER Typical Performance Characteristics (Continued)
(VF of WLED is 3.45V @ IF=20mA, unless otherwise noted )
AP3029
1.40 1.35 1.30
210 208 206
Feedback Voltage (mV)
1.25
204 202 200 198 196 194 192 190 -50
Frequency (MHz)
1.20 1.15 1.10 1.05 1.00 0.95 0.90 -50
-25
0
25
50
o
75
100
-25
0
25
50
o
75
100
Junction Temperature ( C)
Junction Temperature ( C)
Figure 12. Switching Frequency vs. Junction Temperature
Figure 13. Feedback Voltage vs. Junction Temperature
0.80 0.78 0.76
0.50 0.45 0.40
Schottky Forward Drop (V)
0.74 0.72 0.70 0.68 0.66 0.64 0.62 0.60 -50
Schottky Leakage Current (A)
VR=10V VR=16V VR=23V
0.35 0.30 0.25 0.20 0.15 0.10 0.05 0.00 -50
-25
0
25
50
o
75
100
-25
0
25
50
o
75
100
Junction Temperature ( C)
Junction Temperature ( C)
Figure 14. Schottky Forward Drop vs. Junction Temperature
Figure 15. Schottky Leakage Current vs. Junction Temperature
Aug. 2008 Rev. 1. 2 8
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Preliminary Datasheet WHITE LED STEP-UP CONVERTER Typical Performance Characteristics (Continued)
(VF of WLED is 3.45V @ IF=20mA, unless otherwise noted )
AP3029
700
450 400
600
500
Saturation Voltage (mV)
350 300 250 200 150 100 50 50
Current Limit (mA)
400
300
200
-50 C O 25 C O 100 C
40 50 60 70 80 90
O
100 30
100
150
200
250
300
Switch Current (mA)
Duty Cycle (%)
Figure 16. Switch Current Limit vs. Duty Cycle
Figure 17. Switch Saturation Voltage vs. Switch Current
250
Feedback Voltage VFB (mV)
200
150
100
50
0 0.0
0.5
1.0
1.5
2.0
2.5
CTRL Voltage (V)
Figure 18. Feedback Voltage vs. CTRL Pin Voltage
Aug. 2008 Rev. 1. 2 9
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Preliminary Datasheet 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 at 27V. 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 20.
VIN
Control Signal
SW
VOUT
AP3029
CTRL
C2
FB
Figure 20. Soft Start Waveform VIN=3.6V, 5 LEDs, ILED=20mA
C1
GND
R1
Dimming Control
Figure 19. Typical Application circuit to Decide R1
LED Current Control
Refer to Figure 19, 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: Aug. 2008 Rev. 1. 2 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 PWN signal when it is applied on the CTRL pin. The typical frequency of
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Preliminary Datasheet WHITE LED STEP-UP CONVERTER Application Information (Continued)
this PWM signal can be up to 2KHz. Please refer to Figure 21.
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 24.
AP3029
CTRL
up to 2kHz
Figure 21. 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 22.
AP3029
FB VDC
R3 90K R2 5K R1 10
Effective Feedback Voltage
0.1 to 3.6 V
VDC
R1 10k R2 10k
AP3029
CTRL
Figure 24. Dimming Control Using DC Voltage
Second, using a filtered PWM signal can do it. The filtered PWM signal can be considered as a varying and adjustable DC voltage.
Figure 22. 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 23.
AP3029
FB PWM
R4 10K C R3 90K 0.1F R2 5K R1 10
Effective Feedback Voltage
PWM Signal
R1 5k C1 100nF
AP3029
CTRL
Figure 25. Dimming Control Using a Filtered PWM Voltage
Figure 23. 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. Aug. 2008 Rev. 1. 2 11 BCD Semiconductor Manufacturing Limited
Preliminary Datasheet WHITE LED STEP-UP CONVERTER Application Information (Continued)
AP3029
FB Logic Signal R2 2N7002 R1 Effective Feedback Voltage
AP3029
Figure 26. Dimming Control Using Logic Signal
Typical Application
VIN 3V
10
VIN Control Signal 1F CTRL
SW
VOUT 0.22F FB 10
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
Aug. 2008 Rev. 1. 2 12
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Preliminary Datasheet WHITE LED STEP-UP CONVERTER Typical Application (Continued)
VIN 3V
22
AP3029
Control Signal 1F
VIN CTRL
SW
VOUT 0.22F FB 10
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
22
Control Signal 1F
VIN CTRL
SW
VOUT 0.22F FB 10 10
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 27. Typical Application of LED Drivers
Aug. 2008 Rev. 1. 2 13
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Preliminary Datasheet 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) 0.300(0.012) 0.600(0.024)
0 8 0.200(0.008)
6 2.650(0.104) 2.950(0.116)
5
4
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) 0.000(0.000) 0.100(0.004) 0.100(0.004) 0.200(0.008)
1.050(0.041) 1.050(0.041) 1.150(0.045) 1.250(0.049)
Aug. 2008 Rev. 1. 2 14
1.500(0.059) 1.700(0.067)
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Preliminary Datasheet 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) 0.800(0.031)
0.700(0.030) 0.900(0.035)
0.000(0.000) 0.100(0.004)
0.350(0.014) 0.510(0.020)
Aug. 2008 Rev. 1. 2 15
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