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AP8800

Document number: DS31764 Rev. 7 - 2

1 of 13

www.diodes.com

August 2012

P8800

350mA LED STEP-DOWN CONVERTER

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

and SET input pins. Dimming is 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.

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

• SO-8, MSOP-8 and U-DFN3030-10: Available in “Green”

Molding Compound (No Br, Sb) with lead Free Finish/ RoHS

Compliant

 Totally Lead-Free & Fully RoHS Compliant (Notes 1 & 2)

 Halogen and Antimony Free. “Green” Device (Note 3)

Applications

• Commercial & Industrial Lighting

• Small LCD Panel Backlight

• Architecture Detail Lighting

• Appliances Interior Lighting

Pin Assignments

SO-8

( Top View )

RSVD

GND

CTRL

SET

AP8800

MSOP-8

( Top View )

RSVD

GND

CTRL

SET

AP8800

U-DFN3030-10

( Top View )

GND

RSVD

CTRL

SET

AP8800

Notes: 1. No purposely added lead. Fully EU Directive 2002/95/EC (RoHS) & 2011/65/EU (RoHS 2) compliant.

2. See http://www.diodes.com for more information about Diodes Incorporated’s definitions of Halogen and Antimony free, "Green" and Lead-Free.

3. Halogen and Antimony free "Green” products are defined as those which contain <900ppm bromine, <900ppm chlorine (<1500ppm total Br + Cl)

and <1000ppm antimony compounds.

Typical Applications Circuit

Summary of content (13 pages)

PAGE 1
AP8800 350mA LED STEP-DOWN CONVERTER Description Pin Assignments The AP8800 is a step-down DC/DC converter designed to drive LEDs SO-8 with a constant current. The device can drive up to seven LEDs, ( Top View ) 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.
PAGE 2
AP8800 Pin Descriptions Pin Name SW SO-8 3 Pin Number MSOP-8 U-DFN3030-10 3 4 Function Switch Pin. Connect inductor/freewheeling diode here. Minimize trace area at this pin to reduce EMI. GND 4 4 5 GND Pin SET 8 8 10 Set Nominal Output Current Pin. To configure the output current of the device. Dual function dimming control pin. CTRL 1 1 1 • Input voltage of 0.2V or lower forces the device into low current standby mode and shuts off the output.
PAGE 3
AP8800 Recommended Operating Conditions (@TA = +25°C, unless otherwise specified.) Symbol Min Max Operating Input Voltage relative to GND 8.0 28 V VCTRLDC Voltage Range for 24% to 200% DC Dimming Relative to GND (Note 2) 0.3 2.5 V VCTRLL Voltage Low for PWM Dimming Relative to GND VIN fOSC 0 Maximum Switching Frequency TA 0.2 V kHz °C Ambient Temperature Range -40 +85 0.1 0.95 VENH CTRL Input Voltage to Attain 100% LED Current 1.
PAGE 4
AP8800 Application Information AP8800 Operation The AP8800 is a hysteretic LED current switching regulator sometimes known as an equal ripple switching regulator. In normal operation, when voltage is applied at +VIN (See Figure 1), the AP8800 internal switch is turned on. Current starts to flow through sense resistor R1, inductor L1, and the LEDs. The current ramps up linearly, and the ramp rate is determined by the input voltage +VIN, and the inductor L1 (See Figure 2).
PAGE 5
AP8800 Application Information (cont.) Inductor Selection A 100μH inductor is recommended for most AP8800 applications with input voltage at 24V. Figure 3 displays the resulting switching frequency varying the main circuit parameters: Supply voltage, Inductor value and number of LEDs to be driven.
PAGE 6
AP8800 Application Information (cont.) LED Current Dimming The LED current can be dimmed in two ways; 1. Analog Dimming: Where a dc voltage is applied to the CTRL pin or 2. PWM Dimming: Where a Pulse Width Modulated (PWM) signal is applied to the CTRL pin. Analog Dimming If the CTRL pin is driven by an external voltage (lower than 2.5V), the average LED current in this case is: V V ILED = CTRL × TH VREF R SET A DC signal from 0.3V to 2.
PAGE 7
AP8800 Application Information (cont.) PWM Dimming A PWM signal with a max resolution of 8bit can be applied to CTRL regulate the output current to a value below the nominal average value set by resistor RSET. PWM dimming gives a wider average LED current variation and is more accurate at lower average LED currents than by applying DC voltage to the CTRL pin to achieve average LED current dimming. Figure 5 shows the typical PWM response of the AP8800A. An internal filter produces a rump.
PAGE 8
AP8800 Application Information (cont.) Fault conditions The AP8800 is inherently protected against open-LED conditions. If one LED becomes open circuit the device automatically stops switching and will only retart if the open-LED fault is removed. If one or more LEDs should become shorted together then the switching frequency and duty cycle will change. If one or more LEDs get shorted together, the ramp-up time of LED current will become shorter due to there being a larger voltage across the inductor.
PAGE 9
AP8800 Ordering Information AP 8800 XX G - X Package S : SO-8 M8 : MSOP-8 FN : U-DFN3030-10 Part Number Package Code Packaging AP8800SG-13 AP8800M8G-13 AP8800FNG-7 S M8 FN SO-8 MSOP-8 U-DFN3030-10 Green Packing G : Green 7/ 13 : Tape & Reel 7”/13” Tape and Reel Quantity Part Number Suffix 2500/Tape & Reel -13 2500/Tape & Reel -13 3000/Tape & Reel -7 Marking Information SO-8 ( Top View ) 5 8 Logo Part Number G : Green YY : Year : 08, 09,10~ WW : Week : 01~52; 52 represents 52 and 53 week X :
PAGE 10
AP8800 Package Outline Dimensions (All dimensions in mm.) Please see AP02002 at http://www.diodes.com/datasheets/ap02002.pdf for latest version. 0.254 Package Type: SO-8 E1 E A1 L Gauge Plane Seating Plane Detail ‘A’ 7°~9° h 45° Detail ‘A’ A2 A A3 b e SO-8 Dim Min Max A 1.75 A1 0.10 0.20 A2 1.30 1.50 A3 0.15 0.25 b 0.3 0.5 D 4.85 4.95 E 5.90 6.10 E1 3.85 3.95 e 1.27 Typ h 0.35 L 0.62 0.82 0° 8° θ All Dimensions in mm D Package Type: MSOP-8 D 4x 10 ° 0.
PAGE 11
AP8800 Suggested Pad Layout Please see AP02001 at http://www.diodes.com/datasheets/ap02001.pdf for the latest version. Package Type: SO-8 X C1 C2 Dimensions X Y C1 C2 Value (in mm) 0.60 1.55 5.4 1.27 Y Package Type: MSOP-8 X C Y Dimensions Value (in mm) C 0.650 X 0.450 Y 1.350 Y1 5.300 Y1 Package Type: U-DFN3030-10 Y C X1 G X G Dimensions Value (in mm) Z 2.60 G 0.15 X 1.80 X1 0.60 Y 0.30 C 0.50 Z AP8800 Document number: DS31764 Rev. 7 - 2 11 of 13 www.diodes.
PAGE 12
AP8800 Tape Orientation (Note 6) For U-DFN3030-10 Notes: 6. The taping orientation of the other package type can be found on our website at http://www.diodes.com/datasheets/ap02007.pdf. AP8800 Document number: DS31764 Rev. 7 - 2 12 of 13 www.diodes.
PAGE 13
AP8800 IMPORTANT NOTICE 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 MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE (AND THEIR EQUIVALENTS 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.