Diodes AP8803 User Manual

P8803

30V 1A BUCK LED DRIVER

Description

The AP8803 is a step-down DC/DC converter designed to drive LEDs with a constant current. The device can drive up to 7 LEDs, depending on the forward voltage of the LEDs, in series from a voltage source of 8V to 30V. Series connection of the LEDs provides identical LED currents resulting in uniform brightness and eliminating the need for ballast resistors. The AP8803 switches at frequency up to 700kHz. This allows the use of small size external components, hence minimizing the PCB area needed.

Maximum output current of AP8803 is set via an external resistor connected between the V 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 achieved

Features

• LED Driving Current up to 1A

• High Efficiency Up to 92%

• Operating Input Voltage Up to 30V

• High Switching Frequency Up to 700kHz

• PWM/DC Input for Dimming Control

• Built-In Output Open-Circuit Protection

• TSOT25: 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)

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.

Pin Assignments

GND

CTRL

Top View

45SET

Typical Applications Circuit

AP8803

Document number: DS31970 Rev. 5 - 2

12V_DC

CTRL

SET

AP8803

GND

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SET

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Pin Descriptions

Pin Name Function

SW Switch Pin. Connect inductor/freewheeling diode here, minimizing track length at this pin to reduce EMI.

GND GND pin

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

Dimming and On/Off Control Input.

• Leave floating for normal operation. (V

= V

CTRL

= 1.25V giving nominal average output current I

REF

• Drive to voltage below 0.2V to turn off output current

• Drive with DC voltage (0.3V < V

< 1.25V) to adjust output current from 25% to 100% of I

CTRL

OUTnom

= 0.1/RS)

• 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.

VIN Input Supply Pin. Must be locally decoupled to GND with > 2.2µF X7R ceramic capacitor.

Functional Block Diagram

OUTnom

P8803

Absolute Maximum Ratings (@T

= +25°C, unless otherwise specified.)

Symbol Parameter Rating Unit

VIN

VSW

CTRL

Continuous V Transient (t < 0.5s) 40 SW voltage -0.3 to +30 Transient (t < 0.5s) 40

CTRL pin input voltage -0.3 to +6 V

pin voltage -0.3 to +30

ISW Switch current 1.25 A

ESD

Human Body Model ESD 500 V

HBM

ESDMM Machine Model ESD <100 V

TJ Junction Temperature 150 °C

Lead Temperature Soldering 300 °C

LEAD

Storage Temperature Range -65 to +150 °C

Caution: Stresses greater than the 'Absolute Maximum Ratings' specified above, may cause permanent damage to the device. These are stress ratings only;

functional operation of the device at these or any other conditions exceeding those indicated in this specification is not implied. Device reliability may be affected by exposure to absolute maximum rating conditions for extended periods of time.

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

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P8803

Recommended Operating Conditions (@T

= +25°C, unless otherwise specified.)

Symbol Parameter Min Max Unit

VIN Operating Input Voltage 8.0 30 V

Voltage High 0.3 2.5 V

CTRLH

Voltage Low 0.25 V

CTRLL

ISW Continuous Switch Current (Note 5) 1 A

TA Ambient Temperature Range -40 +125 °C

Duty Cycle Using Inductor ≥ 100µH (Note 4) 0.1 0.95

Notes: 4. 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.

5. Refer to Figure 8 for the device derating curve.

Electrical Characteristics (@T

= +25°C, unless otherwise specified.)

Symbol Parameter Conditions Min Typ Max Unit

Internal Regulator Start-Up Threshold VIN rising 5.65 V

INSU

Internal Regulator Shutdown Threshold VIN falling 5.55 V

INSD

IQ Quiescent Current CTRL pin floating f = 250kHz 1.8 5 mA

Internal Threshold Voltage 92 100 108 mV

THD

SET Pin Input Current V

SET

Internal Reference Voltage 1.25 V

REF

On Resistance of MOSFET ISW = 1A 0.5 1 Ω

DS(on)

SET

= V

-0.1 1.25 10 µA

ISW Continuous Switch Current (Note 5) 1 A

SW_Leakage

Notes: 5. Refer to Figure 8 for the device derating curve.

6. Test condition for TSOT25: Device mounted on FR-4 PCB, 25mm x 25mm, 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.

Switch Leakage Current 8 µA

Switching Frequency 0.7 MHz

OSC

Thermal Resistance Junction-to-

Ambient

TSOT25 (Note 6) 125 °C/W

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