Diodes AP1539 User Manual

AP1539

18V 4A 300KHz BUCK CONVERTER

Features

• Input voltage: 3.6V to 18V

• Output voltage: 0.8V to V

• Output current: up to 4A

• Duty ratio: 0% to 99% PWM control

• Oscillation frequency: 300KHz typ.

• Soft-start like, Current limit and Enable function

• Thermal Shutdown function

• Built-in internal SW P-channel MOS

• SOP-8L-DEP: Available in “Green” Molding Compound

(No Br, Sb)

• Lead Free Finish / RoHS Compliant (Note 1)

CC

Applications

• PC Motherboard

• LCD Monitor

• Graphic Card

• DVD-Video Player

• Telecom Equipment

• ADSL Modem

• Printer and other Peripheral Equipment

• Microprocessor core supply

General Description

AP1539 consists of step-down switching regulator with PWM control. These devices include a reference voltage source, oscillation circuit, error amplifier, internal PMOS. AP1539 provides low-ripple power, high efficiency, and excellent transient characteristics. The PWM control circuit is able to vary the duty ratio linearly from 0 up to 99%. This converter also contains an error amplifier circuit as well as a soft-start circuit that prevents overshoot at startup. An enable function, an over current protect function and a short circuit protect function are built inside, and when OCP or SCP happens, the operation frequency will be reduced from 300KHz to 50KHz. Also, an internal compensation block is built in to minimum external component count. With the addition of an internal P-channel Power MOS, a coil, capacitors, and a diode connected externally, these ICs can function as step-down switching regulators. They serve as ideal power supply units for portable devices when coupled with the SOP-8L-DEP mini-package, providing such outstanding features as low current consumption. Since this converter can accommodate an input voltage up to 18V, it is also suitable for the operation via an AC adapter.

Typical Application Circuit

V

= 5V/4A

+

-

OUT

C

0.1uF

+

C

OUT

470uF

-

***

V

IN

R

OCSET

Option

3.9K

C

IN

470uF

CVcc

0.1uF

Notes: * Typical feedback compensation (Cc): 5600pF. ** Suggested DIODES Power Schottky P/N: B540 series or PDS540.

R 100K

C

0.1uF

*** Suggested C

C

EN

OCSET

Vcc

AP 1539

OCSET

EN

V

OUT

=

= 0.7K~5K ohm

R

B

for V

OUT

x (

1+

FB

< 1V; 680uF.

Output

FB

V

SS

R

A

/R

)

B

L1

22uH

Cc

Option*

D1**

R

A

6.8K

R

B

1.3K

AP1539 Rev. 4 1 of 13 OCTOBER 2009 DS31477 www.diodes.com © Diodes Incorporated

Ordering Information

AP 1539 SDP G - 13

Package PackingGreen

AP1539

18V 4A 300KHz BUCK CONVERTER

SDP : SOP-8L-DEP

Device

AP1539SDPG-13 SDP SOP-8L-DEP 2500/Tape & Reel -13

Notes: 1. EU Directive 2002/95/EC (RoHS). All applicable RoHS exemptions applied. Please visit our website at

http://www.diodes.com/datasheets/ap02001.pdf.

http://www.diodes.com/products/lead_free.html

2. Pad layout as shown on Diodes Inc. suggested pad layout document AP02001, which can be found on our website at

Package

Code

Packaging

(Note 2)

G : Green

Quantity Part Number Suffix

13 : Tape & Reel

13” Tape and Reel

Pin Assignments

SOP-8L-DEP (Dual Exposed Pads)

( Top View )

FB

1

Vss

8

1

EN

2

Vss

7

OCSET

3

6

Output

2

4

V

CC

Notes: 3. Exposed pad 1 is connected to VSS and exposed pad 2 is connected to Output. The board layout for exposed pads needs to be considered to

AP1539 Rev. 4 2 of 13 OCTOBER 2009 DS31477 www.diodes.com © Diodes Incorporated

avoid short circuit.

(Note 3)

5

Output

18V 4A 300KHz BUCK CONVERTER

Pin Descriptions

Pin Name

FB 1 Feedback pin

EN 2

OCSET 3 Add an external resistor to set max output current

VCC 4 IC power supply pin

Pin No.

Power-off pin H: Normal operation (Step-down operation) L: Step-down operation s t op p e d (A l l ci rc ui ts de ac t i v a te d)

Description

AP1539

Output 5, 6

VSS 7, 8 GND Pin

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

Block Diagram

Output

Osci ll ation

Circuit

Vcc

PWM-Switched Contro l Circuit

Thermal

Shutdown

EN

AP1539 Rev. 4 3 of 13 OCTOBER 2009 DS31477 www.diodes.com © Diodes Incorporated

Reference Voltage

Source with Soft S tart

+

-

90uA

OCSET

FB

VssV

A

AP1539

18V 4A 300KHz BUCK CONVERTER

Absolute Maximum Ratings

Symbol Parameter Rating Unit

ESD HBM Human Body Model ESD Protection 5.5 KV

ESD MM Machine Model ESD Protection 200 V

VCC VCC Pin Voltage VSS - 0.3 to VSS + 20 V VFB Feedback Pin Voltage VSS - 0.3 to VCC V VEN EN Pin Voltage VSS - 0.3 to VCC V

V

Switch Pin Voltage VSS - 0.3 to VCC V

OUT

PD Power Dissipation Internally limited mW

TJ Operating Junction Temperature Range -40 to +125

T

Storage Temperature Range -65 to +150

ST

Caution: The absolute maximum ratings are rated values exceeding which the product could suffer physical damage. These values must therefore not be exceeded under any conditions.

Recommended Operating Conditions

Symbol Parameter Min Max Unit

VIN Input Voltage (Note 4) 3.6 18 V

I

Output Current 0 4

OUT

TA Operating Ambient Temperature

Notes: 4. For the operations in low input voltage, AP1539 can tolerate down to 3.6V but max output current loading will be less than 4A. For nominal

applications in such low input voltage range, especially lower than 4V, a higher ROCSET with larger heat sink is recommended.

AP1539 Rev. 4 4 of 13 OCTOBER 2009 DS31477 www.diodes.com © Diodes Incorporated

-20 +85

o

C

o

C

o

C

A

AP1539

18V 4A 300KHz BUCK CONVERTER

Electrical Characteristics

IN = 12V, T

(V

Symbol Parameter Conditions Min Typ. Max Unit

VFB Feedback Voltage I

IFB Feedback Bias Current I

I

SHDN

∆V

OUT

/ VIN

∆V

OUT

/ V

OUT

f

Oscillation Frequency Measure waveform at SW pin 240 300 400 KHz

OSC

f

OSC1

VIH

VIL Evaluate oscillation stop at SW pin - - 0.8 ISH

ISL EN Pin Low - -10 - µA

I

OCSET

R

DS(ON)

EFFI Efficiency

T

SHDN

T

Thermal shutdown hysteresis - 55 - °C

HYS

θ

JC

Notes: 5. Test condition for SOP-8L-DEP: Devices mounted on 2oz copper, minimum recommended pad layout on top & bottom layer with thermal vias,

= 25°C, unless otherwise specified)

A

= 0.1A 0.784 0.8 0.816 V

OUT

= 0.1A - 0.1 0.5 µA

OUT

Current Consumption During Power Off

Line Regulation V

Load Regulation I

Frequency of Current Limit or Short Circuit Protection

EN Pin Input Voltage EN Pin Input Leakage Current

V

= 0V - 10 - µA

EN

= 5V~18V - 1 2 %

IN

= 0.1 to 4A - 0.2 0.5 %

OUT

Measure waveform at SW pin - 50 - KHz Evaluate oscillation at SW pin 2.0 - -

V

EN Pin High - 20 - µA

OCSET Pin Bias Current -- 7 5 90 105 µA

Internal MOSFET R

DS(ON)

= 5V, V

V

IN

VIN= 12V, V V

= 12V, V

IN

I

=4

OUT

= 0V - 90 -

FB

= 0V - 50 -

FB

= 5V

OUT

- 92 - %

mΩ

Thermal shutdown threshold - 150 - °C

Thermal Resistance Junction-to-Case

double sided FR-4 PCB.

SOP-8L-DEP (Note 5) - 26 -

o

C/W

AP1539 Rev. 4 5 of 13 OCTOBER 2009 DS31477 www.diodes.com © Diodes Incorporated

AP1539

18V 4A 300KHz BUCK CONVERTER

Typical Performance Characteristics

VIN v s. Frequency

(V

= 3.3V, I

326

OUT

324 322 320 318 316

(kHz)

OSC

314

F

312 310 308 306

024681012141618

= 0.2A)

OUT

0.820

0.815

0.810

0.805

(V)

0.800

FB

V

0.795

0.790

0.785

0.780 0 2 4 6 8 10 12 14 16 18

(V)

V

IN

Line Regulation

(V

= 3.3V, I

3.40

OUT

3.35

3.30

3.25

(V)

3.20

OUT

V

3.15

3.10

3.05

3.00 024681012141618

= 0.2A)

OUT

3.35

3.34

3.33

3.32

3.31

(V)

3.30

OUT

3.29

V

3.28

3.27

3.26

3.25

(V)

V

IN

0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0

Efficiency

(V

= 12V)

100

90 80 70 60 50 40

Efficiency (%)

30 20 10

0

0.0 1.0 2.0 3.0 4.0

IN

7.5

7.0

6.5

6.0

5.5

5.0

4.5

4.0

VOUT=3.3V VOUT=5V

Current Limit (A)

3.5

3.0

2.5 0 2 4 6 8 10 12 14 16 18

(A)

I

OUT

AP1539 Rev. 4 6 of 13 OCTOBER 2009 DS31477 www.diodes.com © Diodes Incorporated

(V

OUT

VIN vs. V

= 3.3V, I

FB

= 0.2A)

OUT

(V)

V

IN

Load Regulation

(V

= 12V)

IN

I

(A)

OUT

Swit c h Cur r e nt Limit

(TA = 25℃)

(V)

V

IN

ROCSET=6.8k ROCSET=4.7k

V

18V 4A 300KHz BUCK CONVERTER

Typical Performance Characteristics (Continued)

Current Limit vs. Temperature

(V

= 12V, R

9.0

8.5

8.0

7.5

7.0

6.5

6.0

5.5

Current Limit (A)

5.0

4.5

4.0

-25 0 25 50 75 100

IN

Ambient Temperature (C)

OCSET

= 6.8k)

AP1539

Ripple

(V

IN

=12V, V

OUT

=3.3V, I

OUT

Load Transient Response

(V

IN

=12V, V

=3.3V, I

OUT

=0.1A)

OUT

=0.1~4A)

OUT

(V

IN

=12V, V

OUT OUT

Ripple

=3.3V, I

OUT

=4.0A)

AP1539 Rev. 4 7 of 13 OCTOBER 2009 DS31477 www.diodes.com © Diodes Incorporated

Test Circuit

18V 4A 300KHz BUCK CONVERTER

open

OUTPUT OUTPUT

CC

OCSET

A

EN

V

SS

Enable function test Feedback function test

open

FBV

Oscillation

A

V

CC

+

-

OCSET EN

V

AP1539

FB

SS

V

CC

+

-

OCSET

EN

Operation function test

OUTPUT

FB

V

SS

+

-

AP1539 Rev. 4 8 of 13 OCTOBER 2009 DS31477 www.diodes.com © Diodes Incorporated

AP1539

18V 4A 300KHz BUCK CONVERTER

Functional Descriptions

PWM Control

The AP1539 is a DC/DC converter that employs pulse width modulation (PWM) scheme. Its pulse width varies in the range of 0% to 99%, based on the output current loading. The output ripple voltage caused by the PWM high frequency switching can easily be reduced through an output filter. Therefore, this converter provides a low ripple output supply over a broad range of input voltage & output current loading

Under Voltage Lockout

The under voltage lockout circuit of the AP1539 assures that the high-side MOSFET driver remains in the off state whenever the supply voltage drops below 3.3V. Normal operation resumes once V

Current Limit Protection

The current limit threshold is set by external resistor R connected from V current I at OCSET pin. When the PWM voltage is less than the voltage at

OCSET, an over-cur rent condition is triggered. The current limit threshold is given by the following equation:

where,

I resistance; F inductor value will affect the ripple current ΔI.

The above equation is recommended for input voltage range of 5V to 18V. For input voltage lower than 5V, higher than 18V or ambient temperature over 100°C, higher R recommended.

The recommended minimum R

rises above 3.5V.

CC

supply to OCSET pin. The internal sink

CC

(90uA typical) across this resistor sets the voltage

OCSET

×=×

RIRI

OCSETOCSETDS(ON)PEAK

)I(Δ

+>

II

OUT(MAX)PEAK

VV

−

I ×

=Δ

is the output peak current; R

PEAK

V

OUT

(V)

0.8 6.8K 3.9K 4.7K

1.0 6.8K 3.9K 4.7K

1.2 6.8K 3.9K 4.7K

1.8 6.8K 3.9K 4.7K

2.5 6.8K 3.9K 4.7K

3.3 6.8K 3.9K 4.7K

5.0 N/A 3.9K 5.6K

is the PWM frequency (300KHz typical). Also, the

S

5V 12V 18V

Lfs

×

DS (ON)

value is summarized below:

OCSET

VIN (V)

2

V

OUTOUTIN

V

IN

is the MOSFET ON

OCSET

is

Inductor Selection

For most designs, the operates with inductors of 22µH to 33µH. The inductor value can be derived from the following equation:

VV

L ×

Where ΔI ripple current and small value inductors result in high ripple current. Choose inductor ripple current approximately 15% of the maximum load current 4A, ∆I inductor should be at least equal to the maximum load current plus half the ripple current to prevent core saturation (4A+0.3A).

Input Capacitor Selection This capacitor should be located close to the IC using short leads and the voltage rating should be approximately 1.5 times the maximum input volta ge. The RMS current rati ng requirement for the input capacitor of a buck regulator is approximately 1⁄2 the DC load current. A low ESR input capacitor sized for maximum RMS current must be used. A 470µF low ESR capacito r for most applications is sufficient.

Output Capacitor Selection The output capacitor is required to filter the output voltage and provides regulator loop stability. The important capacitor parameters are the 100KHz Equivalent Series Resistance (ESR), the RMS ripples current rating, voltage rating and capacitance value. For the output capacitor, the ESR value is the most important parameter . The output ripple can be calculated fro m the following formula.

The bulk capacitor’s ESR will determine the output ripple voltage and the initial voltage drop after a high slew-rate transient.

An aluminum electrolytic capacitor's ESR value is related to the capacitance and its voltage rating. In most case, higher voltage electrolytic capacitors have lower ESR values. Most of the time, capacitors with much higher voltage ratings may be needed to provide the low ESR values required for low output ripple v oltage .

PCB Layout Guide If you need low T SW pins(5& 6) and Vss pins(7& 8)on the SOP-8L package are internally connected to die pad, The evaluation board should be allowed for maximum copper area at output (SW) pins.

1. Connect FB circuits (R

2. Connect C3 to Vcc and Vss pin as closely as possible to get

3. Connect R4 to Vcc and OCSET pin as closely as possible.

4. Connect ground side of the C2 & D1 & C4 as closely as

is inductor Ripple Current. Large value inductors lower

L

& TJ or large PD (Power Dissipation), The dual

C

keep away from inductor flux for pure V good power filter effect.

possible and use ground plane for best performance.

−

=

fs

=0.6A. The DC current rating of the

L

, R2, C1) as closely as possible and

1

V

OUTOUTIN

Δ×

V

I

ΔIV

LRIPPLE

×=

IN

ESR

FB

.

V

Functional Description (Continued)

Keep the gap of exposed pads from short circui t.

Top Side Layout Guid e

AP1539

18V 4A 300KHz BUCK CONVERTER

Recommended exposed-pads gap: 30~40mil (0.75~1mm)

Use vias to conduct the heat into the backside of PCB layer. The heat si nk at output (SW) pins should be allowed for maximum solder-painted area.

Bottom Side Layout Guide

Brown: IC exposed pads. Red: recommended layout. Reference pads layout dimension: Output: 90 x 50 mil

ss: 90 x 60 mil

Functional Description (Continued)

V

IN

Vcc

Output

AP1539

18V 4A 300KHz BUCK CONVERTER

L1

V

OUT

R4

C2

C3

C7

Option

R5

C6

Marking Information

(1) SOP-8L-DEP

Logo

Part No.

AP1539

OCSET

EN

Figure: Layout numbering comparison.

FB

V

SS

C1

Option

D1

( Top View )

8

5

G : Green

: Year : 08, 09,10~

YY

AP1539

WW X

YY

X

E

WW

: Week : 01~52; 52

represents 52 and 53 week

X

: Internal Code

SOP-8L-DEP

41

R1

R2

C8

+

C4

-

+

-

Package Information (All Dimensions in mm)

(1) Package type: SOP-8L-DEP

8

5

8

C

L

1.8 1.8

0.951.65

5

8x-1.55

AP1539

18V 4A 300KHz BUCK CONVERTER

1.0

C

L

5.4

3.85/3.95

2.35

5.90/6.10

EXPOSED PAD

Top View

9

1

.

0

R

0.685

2.15Typ.

i

s

l

a

(

°

1

0.3/0.5

)

e

d

1.27Typ.

4.85/4.95

2.05Typ.

1

0.20

1.7 1. 7

C L

Bottom view

4

1.15Typ.

4

58

0.35Typ.

1.4/1.5

EXPOSED PAD

C

L

0.9

0.713

1

8x-0.60

4

5

°

1.63Max. View"A"

0.15/0.25

0/0.13

View"A"

0

8

/

°

0.254

0.62/0.82

Land Pattem Recommendation (Unit: mm)

4

6x-1.27

Gauge Plane Seating Plane

AP1539

18V 4A 300KHz BUCK CONVERTER

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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 th e user.

B. A critical com ponent is any component in a life sup port devic e or system whose fai lure to perf orm can be reasona bly expected

to cause the failure of the life support device or to affect its safety or effectiveness.

Customers represent that they have all nec essary expertise in the safet y and regulatory ramificati ons 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 indemnif y Diodes Incorporated and its representati ves against any damages arising out of the use of Diodes Incorporated products in such safety-critical, life support devices or systems.

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IMPORTANT NOTICE

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