diodes incorporated AP8801 Service Manual

AP8801

500mA LED Step-down Converter

Features

• LED driving current up to 500mA

• Operating input voltage up to 48V

• High efficiency up to 92%

• High switching frequency up to 500kHz

• PWM/DC input for dimming control

• Built-in output open-circuit protection

• SOP-8L and MSOP-8L are available in “Green”

Molding Compound (No Br, Sb)

• Lead Free Finish/RoHS Compliant (Note 1)

Applications

• Commercial & industrial lighting

• Small LCD panel backlight

• Appliances interior lighting

• Architecture Detail lighting

Typical Application Circuit

General Description

The AP8801 is a step-down DC/DC converter designed to drive LEDs with a constant current. The device can drive up to thirteen LEDs, depending on the forward voltage of the LEDs, in series from a voltage source of 8V to 48V. Series connection of the LEDs provides identical LED currents resulting in uniform brightness and eliminating the need for ballast resistors. The AP8801 switches at f requency up to 500kHz. This allows the use of small size external components, hence minimizing the PCB area needed.

Maximum output current of AP8801 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

24V_DC

CTRL

SET

= 0.43Ω

AP8801

C1= 2.2μF

GND

Figure 1: Typical Application Circuit

AP8801 Rev. 4 1 of 11 DECEMBER 2009 DS31765 www.diodes.com © Diodes Incorporated

L1= 100μH

Ordering Information

AP8801

500mA LED Step-down Converter

AP 8801 XX G - 13

Package Packing

S : SOP-8L

M8 : MSOP-8L

Device

AP8801SG-13 S SOP-8L 2500/Tape & Reel -13 AP8801M8G-13 M8 MSOP-8L 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)

Green

G : Green

13 : Tape & Reel

13” T ape and Reel

Quantity Part Number Suffix

Pin Assignments

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

SET

( Top View )

CTRL

SET

( Top View )

CTRL

GND GND

AP8801 Rev. 4 2 of 11 DECEMBER 2009 DS31765 www.diodes.com © Diodes Incorporated

AP8801

7 6

GND GND

AP8801

7 6

500mA LED Step-down Converter

Pin Descriptions

Pin Name Description

GND GND pin

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

CTRL

VIN Input Supply Pin. Must be locally bypassed. NC No connection

Block Diagram

Switch Pin. Connect inductor/freewheeling diode here, minimizing track length 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.

The input impedance is about 50kΩ, and if the pin is left open V

CTRL

= V

SET

AP8801

REF

CTRL

GND

Sensing

Block

Comparator

PWM/DC

Control

1.25V

REF

Voltage

Regulator

AP8801

Figure 2: AP8801 Block Diagram

AP8801 Rev. 4 3 of 11 DECEMBER 2009 DS31765 www.diodes.com © Diodes Incorporated

AP8801

500mA LED Step-down Converter

Absolute Maximum Ratings

Symbol Parameter Rating Unit

VIN VIN pin voltage -0.3~50 V

VSW SW voltage -0.3~50 V

TJ Junction Temperature 150

Lead Temperature Soldering 300

LEAD

Storage Temperature Range -65 to +150

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

Recommended Operating Conditions

Symbol Parameter Min Max Unit

TA Ambient Temperature Range -40 105 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

Electrical Characteristics (V

Symbol Parameter Conditions Min Typ. Max Unit

Rds(on) On Resistance of MOSFET ISW=0.4A 0.7 1.15 Ω

SW Leakage

Notes: 4. Refer to figure 6 for the device derating curve.

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.

=24V, TA=25oC, unless otherwise specified)

VIN Operating Input Voltage 8.0 - 48 V

Continuous switch current (Note 4) 500 mA

OUT

IQ Quiescent Current - 78 120 μA

Switching Frequency - - 0.5 MHz

OSC

Internal Threshold Voltage 184 200 216 mV

THD

Internal Reference Voltage - 1.25 - V

REF

SET SET pin input current V

-0.2 - 7 - μA

SET=VIN

Switch leakage current - - 8 μA EN Voltage High ON 1.25 - - V EN Voltage Low OFF - - 0.2 V

Thermal Resistance

Junction-to-Ambient Thermal Resistance

Junction-to-Case

5. Test condition for SOP-8L and MSOP-8L: Device mounted on FR-4 PCB, 2”x2”, 2oz copper, minimum recommended pad layout on top layer and thermal vias to bottom layer ground plane. For better thermal performance, larger copper pad for heat-sink is needed.

SOP-8L (Note 5) - 88 MSOP-8L (Note 5) - 128 SOP-8L (Note 5) - 58 MSOP-8L (Note 5) - 90 -

°C/W °C/W °C/W °C/W

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