Diodes AP3019A User Manual

WHITE LED STEP-UP CONVERTER AP3019A

Data Sheet

General Description

The AP3019A is an inductor-based DC/DC converter designed to drive up to eight white LEDs in series 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. Specifically, 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. AP3019A also provides a disable pin to ease its use for different systems.

The output over-voltage protection is implemented in AP3019A. When any LED is broken or in other abnormal conditions, the output voltage will be clamped.

The AP3019A is available in standard SOT-23-6 and TSOT-23-6 packages.

Features

Inherently Uniform LED Current

•

• High Efficiency up to 84%

• No Need for External Schottky Diode

• Output Over-voltage Protection (OVP)

• Fixed 1.2MHz Switching Frequency

• Uses Tiny 1mm Tall Inductor

• Requires Only 0.22µF Output Capaci t or

Applications

• Cellular Phones

• Digital Cameras

• LCD modules

• GPS Receivers

• PDAs, Handheld Computers

SOT-23-6 TSOT-23-6

Figure 1. Package Types of AP3019A

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Data Sheet

WHITE LED STEP-UP CONVERTER AP3019A

Pin Configuration

K/KT Package (SOT-23-6/TSOT-23-6)

Pin 1 Dot by Marking

SW

GND

FB

Figure 2. Pin Configuration of AP3019A (Top View)

1

2

34

V

6

5

IN

V

OUT

CTRL

Pin Description

Pin Number Pin Name Function

1 SW

2 GND

3 FB

4 CTRL

5 V

OUT

6 VIN

Switch pin. Connect external inductor

Ground

Voltage feedback pin. Reference voltage is 200mV

Shutdown and dimming pin. Connect to 1.8V or higher to enable device; Connect to 0.5V or less to disable device; Connect to a PWM signal to achieve LEDs brightness dimming

Output pin. Connect to the cathode of internal Schottky diode

Input supply pin. Must be connected to a local bypass capacitor

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Data Sheet

WHITE LED STEP-UP CONVERTER AP3019A

Functional Block Diagram

Figure 3. Functional Block Diagram of AP3019A

Ordering Information

AP3019A -

Circuit Type

Package K: SOT-23-6 TR: Tape & Reel KT: TSOT-23-6

Package

SOT-23-6

Temperature

Range

-40 to 85°C

Part Number Marking ID Packing Type

AP3019AKTR-G1 GAS Tape & Reel

G1: Green

TSOT-23-6

-40 to 85°C

AP3019AKTTR-G1 L8E Tape & Reel

BCD Semiconductor's Pb-free products, as designated with "G1" suffix in the part number, are RoHS compliant and green.

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Data Sheet

WHITE LED STEP-UP CONVERTER AP3019A

Absolute Maximum Ratings (Note 1)

Parameter Symbol Value Unit

Input Voltage VIN 20 V SW Pin Voltage VSW 38 V Feedback Voltage VFB 20 V CTRL Pin Voltage V

Thermal Resistance (Junction to Ambient, No Heat Sink)

Operating Junction Temperature TJ 150 Storage Temperature Range T Lead T em perature (Soldering, 10sec) T ESD (Machine Model) 250 V ESD (Human Body Model) 2000 V

20 V

CTRL

θ

JA

-65 to 150

STG

260

LEAD

265

°C/W

°C °C °C

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 Symbol Min Max Unit

Operating T em perature Range TOP -40 85 Input Voltage VIN 2.5 16 V CTRL Pin Voltage V

16 V

CTRL

°C

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Data Sheet

WHITE LED STEP-UP CONVERTER AP3019A

Electrical Characteristics

V

=3V, V

IN

Parameter Symbol Conditions Min Typ Max Unit

Minimum Operating Voltage VIN (min) 2.5

Maximum Operating Voltage VIN (max) 16

Feedback Voltage (Note 2) VFB

FB Pin Bias Current IFB 35 100 nA

Quiescent Current IQ VFB=VIN, no switching 1.5 2.5 3.2 mA

=3V, TA =25°C, unless otherwise specified.

CTRL

=20mA, 4 LEDs,

I

OUT

T

=-40oC to 85oC

A

188 200 212

V

mV

Shutdown Quiescent Current I

V

SHDN

=0V 2.0 4.0 6.0

CTRL

µA

Switching Frequency f 0.9 1.2 1.5 MHz

Maximum Duty Cycle D

90 93 %

MAX

D=40% 550

Switch Current Limit (Note 3) I

LIMIT

mA

D=80% 550

Switch VCE Saturation Voltage V

Switch Leakage Current VSW=5V 0.01 5

ISW=250mA 360 mV

CESAT

µA

High 1.8

CTRL Pin Voltage V

CTRL

V

low 0.5

CTRL Pin Bias Current I

CTRL

100

µA

OVP Voltage VOV 30 V

Schottky Forward Drop V

Schottky Leakage Current

ID=150mA 0.7 V

DROP

VR(reverse voltage)=23V 0.1 4

(reverse voltage)=27V 150

V

R

µA

Soft Start Time t 300

Thermal Resistance (Junction to Case)

θ

JC

SOT-23-6 60

TSOT-23-6 60

µS

°C/W

Note 2: The bold type specifications of full temperature range are guaranteed by design (GBD). Note 3: The switch current limit is related to duty cycle. Please refer to Figure 15 for detail.

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Data Sheet

WHITE LED STEP-UP CONVERTER AP3019A

Typical Performance Characteristics

WLED forward voltage (VF) is 3.45V at IF=20mA, unless otherwise noted.

83

82

81

80

79

78

77

Efficiency (%)

76

75

74

73

-50 -25 0 25 50 75 100

Junction Temperature (oC)

VIN=3.6V, I CIN=1µF, C

=20mA, 8 LEDs

OUT

=0.22µF, L=22µH

OUT

86

84

82

80

78

Efficiency (%)

76

74

72

70

3.0 3.5 4.0 4.5 5.0

I

=20mA, 8 LEDs,TA=25OC

OUT

CIN=1µF, C

Input Voltage (V)

=0.22µF, L=22µH

OUT

Figure 4. Efficiency vs. Junction Temperature Figure 5. Efficiency vs. Input Voltage

86

85 84

83 82

81 80

Efficiency (%)

79 78

77 76

2345678

VIN=3.6V, I CIN=1µF, C

LED's Number

=20mA,TA=25OC

OUT

=0.22µF, L=22µH

OUT

Figure 6. Efficiency vs. LED’s Number Figure 7. Schottky Forward Current vs.

350

300

250

200

150

100

Schottky Forward Current (mA)

50

0

0 200 400 600 800 1000

Schottky Forward Drop (mV)

Schottky Forward Drop

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Data Sheet

WHITE LED STEP-UP CONVERTER AP3019A

Typical Performance Characteristics (Continued)

WLED forward voltage (V

) is 3.45V at IF=20mA, unless otherwise noted.

F

30

25

20

15

10

5

Shutdown Quiescent Current (µA)

0

2 4 6 8 10 12 14 16

Input Voltage (V)

TA=25OC

3.5

3.0

2.5

2.0

1.5

1.0

Quiescent Current (mA)

0.5

0.0 0 2 4 6 8 10 12 14 16

TA=-50OC TA=25OC TA=100OC

Input Voltage (V)

Figure 8. Shutdown Quiescent Current vs. Input Voltage Figure 9. Quiescent Current vs. Input Voltage

6.0

5.5

5.0

4.5

4.0

3.5

Input Current (mA)

3.0

2.5

2.0

2.53.03.54.04.55.0

Input Voltage (V)

1.40

1.35

1.30

1.25

1.20

1.15

1.10

Frequency (MHz)

1.05

1.00

0.95

0.90

-50 -25 0 25 50 75 100

Junction Temperature (oC)

Figure 10. Input Current in Output Open Circuit Figure 11. Frequency vs. Junction Temperature

vs. Input Voltage

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Data Sheet

WHITE LED STEP-UP CONVERTER AP3019A

Typical Performance Characteristics (Continued)

WLED forward voltage (V

) is 3.45V at IF=20mA, unless otherwise noted.

F

210

208

206

204

202

200

198

Feedback Voltage (mV)

196

194

192

190

-50 -25 0 25 50 75 100

Junction Temperature (oC)

0.80

0.78

0.76

0.74

0.72

0.70

0.68

0.66

Schottky Forward Drop (V)

0.64

ID=150mA

0.62

0.60

-50 -25 0 25 50 75 100

Junction Temperature (oC)

Figure 12. Feedback Voltage vs. Figure 13. Schottky Forward Drop vs.

Junction Temperature Junction Temperature

0.50

0.45

0.40

0.35

0.30

0.25

0.20

0.15

Schottky Leakage Current (µA)

0.10

0.05

0.00

-50 -25 0 25 50 75 100

Junction Temperature (oC)

VR=10V VR=16V VR=23V

700

600

500

400

300

Current Limit (mA)

200

100

30 40 50 60 70 80 90

Duty Cycle (%)

-50OC 25OC 100OC

Figure 14. Schottky Leakage Current vs. Figure 15. Current Limit vs. Duty Cycle

Junction Temperature

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Data Sheet

WHITE LED STEP-UP CONVERTER AP3019A

Typical Performance Characteristics (Continued)

WLED forward voltage is 3.45V at I

=20mA, unless otherwise noted.

F

450

400

350

300

250

200

150

Saturation Voltage (mV)

100

50

50 100 150 200 250 300

Switch Current (mA)

1.8

1.7

1.6

1.5

1.4

1.3

1.2

1.1

1.0

0.9

CTRL Pin Voltage (V)

0.8

0.7

0.6

0.5

-50 -25 0 25 50 75 100

Junction Temperature (OC)

Figure 16. Saturation Voltage vs. Switch Current Figure 17. CTRL Pin Voltage vs.

Junction Temperature

Falling Edge Rising Edge

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µ

Data Sheet

WHITE LED STEP-UP CONVERTER AP3019A

Application Information

Operation

The AP3019A 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.

Over Voltage Protection

The AP3019A has an internal open-circuit protection circuit. When the LEDs are disconnected from circuit or fail open, the output voltage is clamped. The AP3019A will switch at a low frequency, and minimize input current.

Soft Start

The AP3019A 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.

I

IN

10 0m A/di v

V

OUT

5V /d iv

V

FB

10 0m V/di v

V

CTRL

2V /d iv

Figure 19. Soft Start Waveform

V

IN

Ti me 1 00

=3.6V, 5 LEDs, I

s/ di v

LED

=20mA

Dimming Control

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,

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:

R =

1

May. 2010 Rev. 1.8 BCD Semiconductor Manufacturing Limited

I

mV200

LED

changing the feedback voltage to get appropriate duty and luminous intensity is also useful.

(1) Adding a Control Signal to CTRL Pin Adding a PWM Signal to CTRL pin directly. The AP3019A is turned on or off by the PWM signal when it is applied on the CTRL pin. The typical frequency of this PWM signal can be up to 2kHz. Please refer to Figure 20.

AP3019A

CTRL

up to 2kHz

Figure 20. Dimming Control Using a PWM Signal in

CTRL Pin

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Data Sheet

WHITE LED STEP-UP CONVERTER AP3019A

Application Information (Continued)

(2) Changing the Effective Feedback Voltage There are three methods to change the effective feedback voltage.

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 21.

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.

Figure 21. 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 Filtered PWM

Voltage

Figure 23. Dimming Control Using Logic Signal

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Data Sheet

WHITE LED STEP-UP CONVERTER AP3019A

Typical Application

C: X5R or X7R dielectric L: SUMIDA CDRH5D28R-220NC or equivalent This circuit can work in full temperature

Figure 24. Typical Application of AP3019A

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Data Sheet

WHITE LED STEP-UP CONVERTER AP3019A

Mechanical Dimensions

SOT-23-6 Unit: mm(inch)

2.820(0.111)

3.020(0.119)

0.300(0.012)

0.400(0.016)

6

Pin 1 Dot by Marking

123

5

4

0.300(0.012)

0.600(0.024)

0.700(0.028)REF

0° 8°

0.200(0.008)

0.950(0.037)TYP

1.800(0.071)

2.000(0.079)

0.000(0.000)

0.150(0.006)

0.900(0.035)

1.300(0.051)

1.450(0.057) MAX

0.100(0.004)

0.200(0.008)

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Data Sheet

WHITE LED STEP-UP CONVERTER AP3019A

Mechanical Dimensions (Continued)

TSOT-23-6 Unit: mm(inch)

°

2.800(0.110)

3.000(0.118)

R0.100(0.004)

MIN

0 8

°

1.500(0.059)

1.700(0.067)

0.000(0.000)

0.100(0.004)

0.950(0.037) BSC

0.700(0.028)

0.900(0.035)

Pin 1 Dot by

Marking

1.900(0.075) BSC

0.350(0.014)

0.510(0.020)

2.600(0.102)

3.000(0.118)

1.000(0.039) MAX

GAUGE

PLANE

0.370(0.015) MIN

0.100(0.004)

0.250(0.010)

0.250(0.010) BSC

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