Diodes AL8807B User Manual

A

P

L8807B

Description

The AL8807B is a step-down DC/DC converter designed to drive

LEDs with a constant current. The device can drive up to 9 LEDs,

depending on the forward voltage of the LEDs, in series from a

voltage source of 6V to 36V. Series connection of the LEDs provides

identical LED currents resulting in uniform brightness and eliminating

the need for ballast resistors. The AL8807B switches at frequency up

to 1MHz with controlled rise and fall times to reduce EMI. This

allows the use of small size external components, hence minimizing

the PCB area needed.

Maximum output current of AL8807B is set via an external resistor

connected between the V

achieved by applying a PWM signal at the CTRL input pin. An input

voltage of 0.4V or lower at CTRL switches off the output MOSFET

simplifying PWM dimming.

and SET input pins. Dimming is

IN

NEW PRODUCT

Features

 LED driving current up to 1.3A

 Better than 5% accuracy

 High efficiency up to 96%

 Optimally controlled switching speeds

 Operating input voltage from 6V to 36V

 PWM input for dimming control

 Open-Circuit LED protection

 LED Chain Short Circuited

 Over-Temperature Protection

 MSOP-8EP 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)

Pin Assignments

SET

GND

CTRL

Applications

 MR16 lamps

 General illumination lamps

 12V powered LED Lamps

 24V powered LED Lamps

(Top View)

V

N/C

SW

MSOP-8E

HIGH EFFICIENCY 36V 1.3A PWM DIMMABLE BUCK LED DRIVER

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/quality/lead_free.html 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 Application Circuit

IN

AL88070B

Document number: DS36191 Rev. 1 - 2

PWM Dimming

Input:

VIN:

6 ~ 36V

D1

C1

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R1

IN

V

AL8807B

GND

CTRL

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SETSW

L1

C2

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Pin Descriptions

L8807B

Pin Name

SET 1 Set Nominal Output Current Pin. Configure the output current of the device.

GND 2, 3 GND Pins

CTRL 4

SW 5, 6 Switch Pin. Connect inductor/freewheeling diode here, minimizing track length at this pin to reduce EMI.

N/C 7 no connection

V

IN

EP EP

Number

8

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Functional Block Diagram

Function

Dimming and On/Off Control Input.  Leave floating for normal operation.

(V

= V

CTRL

 Drive to voltage below 0.4V to turn off output current  A PWM signal ( 2.5V) allows the output current to be adjusted below the level set by the resistor

connected to SET input pin.

Input Supply Pin. Must be locally decoupled to GND with > 2.2µF X7R ceramic capacitor – see applications section for more information.

Exposed pad/TAB connects to GND and thermal mass for enhanced thermal impedance. Should not be used as electrical ground conduction path.

= 2.5V giving nominal average output current I

REF

= 0.1/RS)

OUTnom

AL88070B

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Absolute Maximum Ratings

Symbol Parameter Ratings Unit

ESD HBM Human Body Model ESD Protection 2.5 kV

ESD MM Machine Model ESD Protection 200 V

V

IN

V

SW

V

CTRL

I

SW-RMS

I

SW-PK

T

J

T

LEAD

T

ST

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

NEW PRODUCT

Recommended Operating Conditions

Continuous VIN Pin Voltage Relative to GND

SW Voltage Relative to GND -0.3 to +40 V

CTRL Pin Input Voltage -0.3 to +6 V

DC or RMS Switch Current MSOP-8EP 1.6 A

Peak Switch Current (<10%) 2.5 A

Junction Temperature +150 °C

Lead Temperature Soldering +300 °C

Storage Temperature Range -65 to +150 °C

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.

-0.3 to +40 V

L8807B

Symbol Parameter Min Max Unit

V

IN

V

CTRLH

V

CTRLL

f

SW

I

SW

T

J

Electrical Characteristics (V

Symbol Parameter Conditions Min Typ Max Unit

V

INSU

V

INSH

IQ

IS

VTH

V

TH-H

I

SET

R

CTRL

V

REF

R

DS(ON)

tR

tF

T

OTP

T

OTP-Hyst

I

SW_Leakage



JA



JC

Notes: 4. AL8807B does not have a low power standby mode but current consumption is reduced when output switch is inhibited: V tested with V

5. Refer to figure 39 for the device derating curve.

6. Test condition for MSOP-8EP: Device mounted on FR-4 PCB (51mm x 51mm 2oz copper, minimum recommended pad layout on top layer and thermal vias to bottom layer with maximum area ground plane. For better thermal performance, larger copper pad for heat-sink is needed.

7. Dominant conduction path is via exposed pad.

Operating Input Voltage Relative to GND 6.0 36 V

Voltage High for PWM Dimming Relative to GND 2.5 5.5 V

Voltage Low for PWM Dimming Relative to GND 0 0.4 V

Maximum Switching Frequency — 1 MHz

Continuous Switch Current MSOP-8EP — 1.3 A

Junction Temperature Range -40 +125 °C

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

IN

Internal Regulator Start Up Threshold

Internal Regulator Hysteresis Threshold Quiescent Current Output not switching (Note 4) — — 350 µA

Input Supply Current CTRL pin floating f = 250kHz — 1.8 5 mA

Set Current Threshold Voltage

Set Threshold Hysteresis

SET Pin Input Current

CTRL Pin Input Resistance Referred to internal reference — 50 — k

Internal Reference Voltage

On Resistance of SW MOSFET

SW Rise Time

SW Fall Time — 20 — ns

Over-Temperature Shutdown

Over-Temperature Hysteresis

Switch Leakage Current

Thermal Resistance Junction-toAmbient (Note 5)

Thermal Resistance Junction-to-case (Note 7)

 2.5V.

CTRL

VIN rising

VIN falling

—

V

= VIN-0.1

SET



ISW = 1A

V

= 100 ±20mV fSW = 250kHz

SENSE

VSW = 0.1V~12V~0.1V CL = 15pF

—

VIN =36V

(Note 6) — 69 — °C/W

(Note 6) — 4.3 — —

— — 5.9 V

100 — 300 mV

95 100 105 mV

— ±15 — mV

— 16 22 µA

— 2.5 — V

— 0.25 0.4 

— 12 — ns

— 155 — °C

— 55 — °C

— — 0.5 A

= 0V. Parameter is

SENSE

AL88070B

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(°C)

R

p

R

Typical Performance Characteristics (@T

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400

350

300

250

200

IN

I (µA)

150

100

50

0

0 3 6 9 15 18 21 24 27 30 33

12 36

V (V)

IN

Figure 1. Supply Current (not switching) vs.

Input Voltage

3

2.5

2

V = 0V

CTRL

V = V

SET IN

T = 25°C

A

= +25°C, unless otherwise specified.)

A

80

V = V = 12V

SET IN

60

T = 25°C

A

40

)

20

CTRL

0

I (µ

-20

-40

-60

0.0 0.5 1.0 1.5 2.5 3.0 3.5 4.0 4.5 5.0

2.0 5.0 V (V)

Figure 2 I

2.52

2.51

CTRL

vs. V

CTRL

V = Open

CTRL

V = V= 12V

SET IN

L8807B

1.5

CTRL

V (V)

2.50

CTRL

V (V)

1

V = Open

CTRL

0.5

0

0 3 6 9 12 18 21 24 27 30 36

Figure 3 V

15 33

V (V)

IN

vs. Input Voltage

CTRL

(CTRL Pin open circuit)

V = V

SET IN

T = 25°C

A

300

2.49

2.48

-40 -15 10 35 60 85 110 AMBIENT TEMPERATURE

Figure 4 V

vs. Temperature

CTRL

400

270

240

210



180

(m )

150

DS(ON)

120

90

60

30

0

6 9 12 18 21 24 27 30 36

15 33

Figure 5 SW R

V (V)

IN

vs. Input Voltage

DS(ON)

V = Open

CTRL

V = V

SET IN

T = 25°C

A

350

300



(m )

250

DS(ON)

200

150

100

-40 -15 35 60 11010 85 Ambient Tem

Figure 6 SW R

eratur e (C)

vs. Temperature

DS(ON)

V = Open

CTRL

V = V= 12V

SET IN

AL88070B

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Typical Performance Characteristics

(cont.) (@TA = +25°C, unless otherwise specified.)

L8807B

NEW PRODUCT

Figure 7 I

Figure 9. Efficiency vs. Input Voltage

vs. PWM Duty Cycle

LED

Figure 8. Duty Cycle vs. Input Voltage

Figure 10. On-time vs. Input Voltage

Figure. 11 SW Output Rise Time Figure. 12 SW Output Fall Time

AL88070B

Document number: DS36191 Rev. 1 - 2

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Typical Performance Characteristics

(670mA LED current) (@TA = +25°C, unless otherwise specified.)

L8807B

NEW PRODUCT

Figure 13. LED Current Deviation vs. Input Voltage

Figure 15. LED Current Deviation vs. Input Voltage

Figure 14. Switching Frequency vs. Input Voltage

Figure 16. Switching Frequency vs. Input Voltage

AL88070B

Document number: DS36191 Rev. 1 - 2

Figure 17. LED Current Deviation vs. Input Voltage

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Figure 18. Switching Frequency vs. Input Voltage

March 2014