diodes incorporated AP8800 Service Manual

AP8800

350mA LED Step-down Converter

Features

• LED driving current up to 350mA

• Compatible with 12V & 24V standard systems

• High efficiency up to 92%

• High switching frequency up to 0.6MHz

• PWM/DC input for dimming control

• Built-in soft-start function

• Built-in output open-circuit protection

• SOP-8L, MSOP-8L and DFN3030-10 are available in

“Green” Molding Compound (No Br, Sb)

• Lead Free Finish/RoHS Compliant (Note 1)

Applications

• Commercial & Industrial lighting

• Small LCD panel backlight

• Architecture Detail lighting

• Appliances interior lighting

Typical Application Circuit

General Description

The AP8800 is a step-down DC/DC converter designed to drive LEDs with a constant current. The device can drive up to seven LEDs, depending on the forward voltage of the LEDs, in series from a voltage source of 8V to 28V. Series connection of the LEDs provides identical LED currents resulting in uniform brightness and eliminates the need for ballast resistors. The AP8800 switches at frequency up to 0.6MHz. This allows the use of small size external components, hence minimizing the PCB area needed.

Maximum output current of AP8800 is set via an external resistor connected between the V achieved by applying either a DC voltage or a PWM signal at the CTRL input pin. An input voltage of 0.2V or lower at CTRL shuts down the output at SW and puts the device into a low-current standby state.

and SET input pins. Dimming is

IN

Figure 1: Typical Application Circuit

AP8800 Rev. 4 1 of 13 DECEMBER 2009 DS31764 www.diodes.com © Diodes Incorporated

Ordering Information

AP8800

350mA LED Step-down Converter

AP 8800 XX G - X

Package Packing

S : SOP-8L

M8 : MSOP-8L

FN : DFN3030-10

Device

AP8800SG-13 S SOP-8L 2500/Tape & Reel -13 AP8800M8G-13 M8 MSOP-8L 2500/Tape & Reel -13 AP8800FNG-7 FN DFN3030-10 3000/Tape & Reel -7

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.

AP8800 Rev. 4 2 of 13 DECEMBER 2009 DS31764 www.diodes.com © Diodes Incorporated

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)

Green

G : Green

7/ 13 : Tape & Reel

7”/13” Tape and Reel

Quantity Part Number Suffix

350mA LED Step-down Converter

Pin Assignments

(1) SOP-8L (2) MSOP-8L

AP8800

CTRL

RSVD

SW

GND

(3) DFN3030-10

CTRL

RSVD

NC

SW

GND

( Top View )

1

2

AP8800

3

45

( Top View )

1

2

3

AP8800

4

5

SET

8

NC

7

NC

6

V

IN

10

SET

9

NC

8

NC

7

NC

6

V

IN

( Top View )

CTRL

RSVD

SW

GND

1

2

AP8800

3

45

SET

8

NC

7

NC

6

V

IN

Pin Descriptions

Pin Name Description

SW

GND GND pin

SET Set Nominal Output Current Pin. To configure the output current of the device.

CTRL

VIN Input Supply Pin. Must be locally bypassed.

RSVD Reserved. Normally connected to Ground

NC No Connection.

AP8800 Rev. 4 3 of 13 DECEMBER 2009 DS31764 www.diodes.com © Diodes Incorporated

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

Dimming and On/Off Control Input. Input voltage of 0.2V or lower forces the device into low current standby mode and shuts off the output. A PWM signal allows the output current to be adjusted above or below the level set by the resistor connected to SET input pin.

= V

The input impedance is about 200kΩ, and if the pin is left open V

CTRL

REF

Block Diagram

V

IN

Voltage

Regulator

AP8800

350mA LED Step-down Converter

SET

SW

Sensing

Block

5V

Comparator

CTRL

GND

PWM/DC

Control

V

1.25V

REF

AP8800

R

Figure 2: AP8800 Block Diagram

Absolute Maximum Ratings

Symbol Parameter Rating Unit

VIN VIN pin voltage -0.3~30 V

VSW SW voltage -0.3~30 V

TJ Maximum Junction Temperature 125

T

Maximum Lead Temperature 300

LEAD

T

Storage Temp erature Range -65 to +125

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 condition. Semiconductor devices are ESD sensitive and may be damaged by exposure to ESD events. Suitable ESD precautions should be taken when handling and transporting these devices.

o

C

o

C

o

C

Recommended Operating Conditions

Symbol Parameter Min Max Unit

TA Ambient Temperature Range -40 85 ºC

Duty Cycle Using Inductor ≥ 100µH (Note 3) 0.1 0.95

Notes: 3. For most applications the LED current will be within 8% over the duty cycle range specified. Duty cycle accuracy is also dependent on

propagation delay. Smaller size inductors can be used but LED current accuracy may be greater than 8% at extremes of duty cycle. This is most noticeable at low duty cycles (less than 0.1) or when the input voltage is high and only one LED is being driven.