Diodes AP1534 User Manual

PWM CONTROL 2A STEP-DOWN CONVERTER

Description

AP1534 consists of step-down switching regulator with PWM control. These devices include a reference voltage source, oscillation circuit, error amplifier, internal PMOS.

AP1534 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 minimize 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 SO-8 mini-packages, 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.

Pin Assignments

1

FB

2

EN

OCSET

3

V

4

CC

(Top View)

AP1534

SO-8

AP1534

V

8

SS

V

7

SS

Output

6

Output

5

Features

• Input voltage: 3.6V to 18V

• Output voltage: 0.8V to V

• Duty ratio: 0% to 99% PWM control

• Oscillation frequency: 300KHz typical

• Current limit, Enable function

• Thermal Shutdown function

• Built-in internal SW P-channel MOS

• SO-8: Available in “Green” Molding Compound

(No Br, Sb)

• Lead Free Finish/RoHS Compliant (Note 1)

Notes: 1. EU Directive 2002/95/EC (RoHS). All applicable RoHS exemptions applied. Please visit our website at http://www.diodes.com/products/lead_free.html.

CC

Applications

• PC Motherboard

• LCD Monitor

• Graphic Card

• DVD-Video Player

• Telecom Equipment

• ADSL Modem

• Printer and other Peripheral Equipment

• Microprocessor Core Supply

Typical Application Circuit



OCSET

Vcc

OCSET

EN

AP1534

Output

FB

V

SS

V

IN

C

IN

470uF

R

5.6K

CVcc

0.1uF

OCSET

C

Option

R

EN

100K C

EN

0.1uF

22uH

L1

C

Optional

D1

B240A

(Note 2)

C

R

A

6.8K

R

B

1.3K

V

OUT

+

-

+

C

0.1uF 470uF

-

=5V/2A

C

OUT

Notes: 2. Suggested DIODES Power Schottky P/N: B240/B340 series.

AP1534

Document number: DS31314 Rev. 6 - 2

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Note: V = V x (1+R /R ) R = 0.7K~5K

OUT FB A B

B

Ω

April 2011

PWM CONTROL 2A STEP-DOWN CONVERTER

Pin Descriptions

Pin Name Pin No. Description

FB 1 Feedback pin

Power-off pin H: Normal operation

EN 2

(Step-down operation) L: Step-down operation stopped (All circuits deactivated)

OCSET 3 Add an external resistor to set max output current

VCC

Output 5, 6

VSS

4 IC power supply pin

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

7, 8 GND Pin

Functional Block Diagram

AP1534

Output

Oscillation

Circuit

Vcc

PWM-Switched Control Circuit

Thermal

Shutdown

EN

Reference Voltage

Source

100uA

OCSET

+

FB

-

VssV

Absolute Maximum Ratings

Symbol Parameter Rating Unit

ESD HBM Human Body Model ESD Protection 4.5 KV

ESD MM Machine Model ESD Protection 150 V

VCC VFB VEN

V

OUT

PD

TJ

T

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.

VCC Pin Voltage Feedback Pin Voltage EN Pin Voltage Switch Pin Voltage Power Dissipation Internally limited mW Operating Junction Temperature Range -40 to +125 Storage Temperature Range -65 to +150

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VSS - 0.3 to VSS + 20

VSS - 0.3 to VCC

VSS - 0.3 to VIN VSS - 1.0 to VIN

V V V V

o

C

o

C

April 2011

AP1534

Recommended Operating Conditions

Symbol Parameter Min Max Unit

VIN

I

OUT

TA

Electrical Characteristics (V

Symbol Parameter Conditions Min Typ. Max Unit

VFB

IFB

ISW

I

SHDN

∆V

OUT

/ VIN

∆V

OUT

/V

OUT

f

OSC

f

OSC1

VIH VIL ISH

ISL

I

OCSET

R

Notes: 3. Test condition for SO-8: Device mounted on FR-4 substrate PC board, 2oz copper, with minimum recommended pad layout. For better thermal performance, larger copper pad for heatsink is needed.

Internal MOSFET R

DS(ON)

EFFI Efficiency

T

SHDN

T

HYS

θ

JA

θ

JC

Input Voltage 3.6 18 V Output Current 0 2 A Operating Ambient Temperature -20 85

= 12V, TA = 25°C, unless otherwise specified)

IN

Feedback Voltage Feedback Bias Current Switch Current -- 2.0 - - A Current Consumption During Power Off

Line Regulation

Load Regulation Oscillation Frequency Measure waveform at SW pin 240 300 400 KHz

Frequency of Current Limit or Short Circuit Protect

EN Pin Input Voltage

EN Pin Input Leakage Current OCSET Pin Bias Current -- 75 90 105 µA

DS(ON)

Thermal shutdown threshold - 150 - °C Thermal shutdown hysteresis - 55 - °C

Thermal Resistance Junction-to-Ambient SO-8 (Note 3) - 127 Thermal Resistance Junction-to-Case SO-8 (Note 3) - 28 -

PWM CONTROL 2A STEP-DOWN CONVERTER

o

C

I

= 0.1A

OUT

I

= 0.1A

OUT

V

= 0V

EN

V

= 5V~18V

IN

I

= 0.1 to 2A

OUT

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

Evaluate oscillation stop at SW pin - - 0.8

-- - 20 - µA

-- - -10 - µA

V

IN

V

IN

V

IN

= 5V, V = 12V, V = 12V, V

FB

= 0V

FB OUT

= 0V

= 5V, I

OUT

= 2A

0.784 0.8 0.816 V

- 0.1 0.5 µA

- 10 - µA

- 1 2 %

- 0.2 0.5 %

- 160 -

- 100 -

- 91 - %

o

V

mΩ

C/W C/W

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F (k

H

C

A

G

E (%

C

E (%

Typical Performance Characteristics

326

V = 3.3V,

OUT

324

I = 0.2A

OUT

322 320 318

z)

316

OSC

314 312

310 308

306

0 2 4 6 8 1012141618

3.0%

V = 3.3V,

OUT

I = 0.2A

OUT

2.0%

)

1.0%

N

0.0%

H

-1.0%

OUT

V

-2.0%

-3.0%

024681012141618

100

90



80

V = 5V

70

OUT

60 50

V (V)

IN

V vs. Frequency

IN

V (V)

IN

Line Regulation

V = 3.3V

OUT

AP1534

PWM CONTROL 2A STEP-DOWN CONVERTER

0.820

0.815

0.810

0.805

0.800

FB

V (V)

0.795

0.790

0.785

0.780

1.0%

0.8%

0.6%

0.4%

)

0.2%

0.0%

HANG

-0.2%

OUT

-0.4%

V

-0.6%

-0.8%

-1.0%

V = 3.3V,

OUT

I = 0.2A

OUT

024681012141618

V (V)

IN

V vs. V

IN FB

V = 5V,

IN

V = 3.3V

OUT

0.0 0.5 1.0 1.5 2.0 I (A)

OUT

Load Regula tio n

40

EFFICIENCY (%)

30 20 10

0

0.0 0.5 1.0 1.5 2.0 I (A)

OUT

Efficiency

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Typical Performance Characteristics (cont.)

V

Ripple

OUT

(V

= 5V, V

IN

OUT

= 3.3V, I

OUT

= 0.1A)

AP1534

PWM CONTROL 2A STEP-DOWN CONVERTER

V

Ripple

OUT

(V

= 5V, V

IN

OUT

= 3.3V, I

OUT

= 2A)

Test Circuit

+

-

open

OUTPUT OUTPUT

CC

OCSET

A

EN

V

SS

Enable function test Feedback functio n test

V

CC

OCSET EN

OUTPUT

V

FB

SS

open

FBV

Oscillation

+

-

V

A

+

-

V

CC

OCSET EN

V

FB

SS

Operation function test

AP1534

Document number: DS31314 Rev. 6 - 2

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AP1534

R

Functional Description

PWM Control

The AP1534 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 AP1534 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 VCC supply to OCSET pin. The

OCSET

internal sink current I resistor sets the voltage at OCSET pin. When the PWM voltage is less than the voltage at OCSET, an overcurrent condition is triggered.

The current limit threshold is given by the following equation:

where,

I ×

=Δ

I

is the output peak current; R

PEAK

ON resistance; F

is the PWM frequency (300KHz

S

typical). Also, the 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 or ambient temperature over 100°C, higher R recommended.

The recommended minimum R summarized below:

VIN (V) V

OUT

4 1 6.8K

5 3.3 5.6K 12 5 3.9K 18 12 4.7K

AP1534

Document number: DS31314 Rev. 6 - 2

rises above 3.5V.

CC

(90uA typical) across this

OCSET

×=×

RIRI

OCSETOCSETDS(ON)PEAK

Δ

I)(

+>

II

VV

−

OUTIN

S

LF

×

(V) R

(MAX) OUTPEAK

V

DS (ON)

2

OUT

IN

V

is the MOSFET

OCSET

(Ω)

OCSET

value is

PWM CONTROL 2A STEP-DOWN CONVERTER

Inductor Selection

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

OUT

I

Δ×

V

OUT V

IN

I

ES

L

April 2011

Where ΔI inductors lower ripple current and small value inductors result in high ripple current. Choose inductor ripple current approximately 15% of the maximum load current 2A, ∆I should be at least equal to the maximum load current plus half the ripple current to prevent core saturation (2A+0.15A).

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 voltage. The RMS current rating 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 capacitor 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 from the following formula.

is

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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 voltage.

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V

−

IN

L ×

=

f

S

is inductor Ripple Current. Large value

L

=0.3A. The DC current rating of the inductor

L

V ×Δ=

RIPPLE

Functional Description (cont.)

PWM CONTROL 2A STEP-DOWN CONVERTER

PCB Layout Guide

If you need low TC & TJ or large PD (Power Dissipation), The dual SW pins (5 & 6) and V

SO-8 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 (RA, RB, CC) as closely as possible and keep away from inductor flux for pure

V

.

FB

2. Connect C possible to get good power filter effect.

3. Connect R possible.

4. Connect ground side of the CIN & D1 & C as possible and use ground plane for best performance.

to Vcc and Vss pin as closely as

VCC

to Vcc and OCSET pin as closely as

OCSET

pins(7 & 8)on the

SS

as closely

OUT

Connect FB circuits closer and keep away from L1.

Top Side Layout Guide

AP1534

Bottom Side Layout Guide

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

V

IN

R4

C2

+

-

C3

+

-

AP1534

Document number: DS31314 Rev. 6 - 2

C7

Option

R5

C6

Vcc

Output

AP1534

OCSET

EN

FB

V

SS

Layout numbering comparison

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L1

Option

D1

C1

R1

R2

+

C8

-

V

OUT

+

C4

-

April 2011

A

θ

Ordering Information



AP1534

PWM CONTROL 2A STEP-DOWN CONVERTER

P 1534 SG -13

Package Packing

SO-8

S :

Green

G : Green

13 : Tape & Reel

Device

AP1534SG-13 S SO-8 2500/Tape & Reel -13

Note: 4. Pad layout as shown on Diodes Inc. suggested pad layout document AP02001, which can be found on our website at http://www.diodes.com/datasheets/ap02001.pdf.

Package

Code

Packaging

(Note 4)

Quantity Part Number Suffix

13” Tape and Reel

Marking Information

(1) SO-8

( Top View )

5

G : Green

YY

: Year : 08, 09,10~

X

41

represents 52 and 53 week

WW : Week : 01~52; 52

X

: Internal Code

Logo

Part Number

8

AP1534 YY

WW

Package Outline Dimensions (All Dimensions in mm)

(1) Package Type: SO-8

e

b

D

AP1534

Document number: DS31314 Rev. 6 - 2

E1

A2

SO-8

Dim Min Max

- 1.75

1

0.10 0.20

2

E

A1

Detail ‘A’

h

°

45

A3

A

www.diodes.com

L

0.254

Gauge Plane Seating Plane

7°~9

°

8 of 9

E1

Detail ‘A’

All Dimensions in mm

1.30 1.50

3

0.15 0.25

b D E

e

h

L

0.3 0.5

4.85 4.95

5.90 6.10

3.85 3.95

1.27 Typ

- 0.35

0.62 0.82 0° 8°

April 2011

AP1534

DIODES INCORPORATED MAKES NO WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, WITH REGARDS TO THIS DOCUMENT, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTA BILITY AND FITNESS FOR A PARTICULAR PURPOSE (AND THEIR EQUIV ALENTS UNDER THE LAWS OF ANY JURISDICTION).

Diodes Incorporated and its subsidiaries reserve the right to make modifications, enhancements, improvements, corrections or other changes without further notice to this document and any product described herein. Diodes Incorporated does not assume any liability arising out of the application or use of this document or any product described herein; neither does Diodes Incorporated convey any license under its patent or trademark rights, nor the rights of others. Any Customer or user of this document or products described herein in such applications shall assume all risks of such use and will agree to hold Diodes Incorporated and all the companies whose products are represented on Diodes Incorporated website, harml ess against all damages.

Diodes Incorporated does not warrant or accept any li ability whatsoever in respec t of any products purc hased through unauthorized sales channel. Should Customers purchase or use Diodes Incorporated products for any unintended or unauthorized application, Customers shall indemnify and hold Diodes Incorporated and its representatives harml ess against all claims, damages, expenses, and attorney fees arising out of, directly or indirectly, any claim of personal inj ury or death ass oci ated with such unintended or unauthorized application.

Products described herein may be covered by one or more United Stat es, international or foreign patents pending. Product names and markings noted herein may also be covered by one or more United States, international or foreign trademarks.

Diodes Incorporated products are specifically not authorized for use as critical components in life support devices or systems without the express written approval of the Chief Executive Officer of Diodes Incorporated. As used herein:

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 inst ruct i ons for us e provided in the labeling can be reasonably expected to result in significant injury to the user.

B. A critical component is any component in a life support device or system whose failure to perform can be reasonably expected

to cause the failure of the life support device or to affect its safety or eff ect i veness.

Customers represent that they have all necessary expertise in the safety and regulatory ramifications 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 indemnify Diodes Incorporated and its representatives against any damages arisi ng out of the use of Diodes Incorporated products in such safety-critical, life support devices or systems.

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PWM CONTROL 2A STEP-DOWN CONVERTER

IMPORTANT NOTICE

LIFE SUPPORT

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