Diodes AP5724 User Manual

A

Pb

P5724

WHITE LED STEP-UP CONVERTER

Description

The AP5724 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, 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

the current setting resistor for better efficiency

Pin Assignments

(Top View)

1

SW

2

GND

3

FB

SOT26 / TSOT23-6

(Top View)

VIN

6

5

OVP

7

4

EN

Features

1

• 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”

Molding Compound (No Br, Sb)

• Lead-Free Finish; RoHS Compliant (Notes 1 & 2)

Notes: 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.

Applications

• Cellular Phones

• PDAs, Hand held Computers

• Digital Cameras

• MP3 Players

• GPS Receivers

SW

2

V

IN

OVP

3

U-DFN2020-6

6

GND

5

FB

4

EN

Typical Applications Circuit

V

IN

OFFON

PWM Dimming

AP5724

Document number: DS31843 Rev. 4 - 2

C

1uF

L1

22uH

IN

V

IN

AP5724

EN

D1

SW

OVP

FB

GND

Figure 1 Typical Application Circuit

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R

SET

5

2~6 LEDs

C

OUT

1uF

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Pin Descriptions

Pin Name Functions

SW Switch Pin. Connect inductor/diode here. Minimize trace area at this pin to reduce EMI.

GND GND pin.

FB

EN

OVP Output Voltage detect pin for over voltage protection.

VIN

Feedback Pin. Reference voltage is 0.1V. Connect cathode of lowest LED and a sense resister here. Calculate resistor value according to the formula: R

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.

Input Supply Pin. Must be locally bypassed with 1μF or 2.2μF to reduce input noise.

= 0.1V / ILED

SET

Functional Block Diagram

P5724

OVP

5

1

Comparator

-

A2

+

Rc

A1

-

+

FB

3

V

6

IN

REF

0.1V

Cc

Σ

OTP

CONTROL

LOGIC

Driver

+

SW

Q1

-

RAMP

Generator

4

EN

Absolute Maximum Ratings (@T

Symbol Parameter Rating Unit

VIN

VSW SW Voltage -0.3 to +34 V

V

OVP

VFB

EN EN -0.3 to +7 V

T

J(MAX)

T

LEAD

T

ST

Caution: Operation above the absolute maximum ratings can cause device failure. These values, therefore, must not be exceeded under any condition.

AP5724

Document number: DS31843 Rev. 4 - 2

Operation at the absolute maximum rating for extended periods, may reduce device reliability.

Enable

1.2MHz

Oscillator

= +25°C, unless otherwise specified.)

A

VIN Pin Voltage -0.3 to +7 V

OVP Pin Voltage -0.3 to +35 V

Feedback Pin Voltage -0.3 to +7 V

Maximum Junction Temperature 150 °C

Lead Temperature 300 °C

Storage Temperature Range -65 to +150 °C

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2

GND

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P5724

Recommended Operating Conditions (@T

Symbol Parameter Min Max Unit

VIN

TJ

TA

Electrical Characteristics (@ V

Symbol Parameter Conditions Min Typ Max Unit

System Supply Input

VIN

UVLO Under Voltage Lockout — 2.2 2.4 V

Under Voltage Lockout Hysteretic — 85 — mV

IQ

ISD

Oscillator

F

OSC

Dmax Maximum Duty Cycle 86 90 — %

Reference Voltage

VFB

IFB

MOSFET

Rds(on) On Resistance of MOSFET — 0.95 1.2 Ω

I

OCP

Control and Protection

EN Voltage High ON 1.5 — — V EN Voltage Low OFF — — 0.4 V

IEN

OVP OVP Threshold 26 30 34 V

θJA

θJC

Note: 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

Input Voltage 2.7 5.5 V

Operating Junction Temperature -40 125 °C

Operating Ambient Temperature -40 85 °C

= 3.6V, TA = +25°C, unless otherwise specified.)

IN

Operating Input Voltage 2.7 — 5.5 V

Quiescent Current FB = 0.2V, No Switching — 500 — μA

Shutdown Current

Operation Frequency 1 1.2 1.4 MHz

Feedback Voltage 0.09 0.1 0.11 V

FB Pin Bias Current 10 45 100 nA

Switching Current Limit Normal Operation — 750 — mA

EN Pin Pull Low Current — 4 6 μA

Thermal Resistance Junction-to-Ambient

Thermal Resistance Junction-to-Case

= +25°C, unless otherwise specified.)

A

VEN < 0.4V

SOT26 (Note 3) — 162 —

U-DFN2020-6 (Note 3) — 200 —

SOT26 (Note 3) — 36 —

TSOT26 (Note 3) — 32 —

U-DFN2020-6 (Note 3) — 30 —

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— 0.1 1 μA

°C/W TSOT26 (Note 3) — 152 —

°C/W

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Typical Performance Characteristics (6 LEDS, V

= 3.6V, I

IN

= 25mA)

OUT

P5724

VIN vs. Shutdown Current

1

0.8

0.6

0.4

0.2

Shutdown Current(uA)

0

2.5 3 3.5 4 4.5 5 5.5

V

(V)

IN

VIN vs. Frequency

1.25

1.2

1.15

1.1

Frequency(MHz)

1.05

V

vs. Quiescent Current

IN

700

600

500

400

300

200

100

Quiescent Current(uA)

0

2.5 3 3.5 4 4.5 5 5.5

100

95

90

Max Duty(%)

85

V

(V)

IN

VIN vs. Max Duty

1

2.5 3 3.5 4 4.5 5 5.5

VIN vs. Feedback Voltage

0.12

0.11

0.1

0.09

0.08

Feedback Voltage(V)

0.07

0.06

2.5 3 3.5 4 4.5 5 5.5

AP5724

Document number: DS31843 Rev. 4 - 2

80

V

(V)

IN

(V)

V

IN

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2.533.544.555.5

(V)

V

IN

I

vs. Feedback Voltage

OUT

0.12

0.11

0.1

0.09

0.08

0.07

Feedback Voltage(V)

0.06 0 1020304050

I

OUT

(mA)

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Typical Performance Characteristics (cont.) (6 LEDS, V

= 3.6V, I

IN

= 25mA)

OUT

P5724

VIN vs. OVP Threshold

35

33

31

29

27

OVP Threshold(V)

25

2.5 3 3. 5 4 4. 5 5 5.5

(V)

V

IN

Temperature vs. OVP Threshold

35

30

25

20

Temperature vs. Shutdown Current

1

0.8

0.6

0.4

0.2

Shutdown Current(uA)

0

-50 -25 0 25 50 75 100 125

Temperature (℃)

Tem perature vs. Frequency

1.7

VIN = 4.2V

1.4

1.1

0.8

VIN = 3.6V

OVP Threshold(V)

15

10

-50 -25 0 25 50 75 100 125

Temperature vs. Feedback Voltage

120

110

100

90

80

Feedback Voltage(mV)

70

60

-50 -25 0 25 50 75 100 125

AP5724

Document number: DS31843 Rev. 4 - 2

Temperature (℃)

VIN = 4.2V

VIN = 3.6V

Temperature (℃)

Frequency (MHZ)

0.5

0.2

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-50 -25 0 25 50 75 100 125

Temperature (℃)

December 2013