Diodes AL8807 User Manual

A

V

A

L8807

HIGH EFFICIENCY LOW 36V 1A BUCK LED DRIVER

Description

The AL8807 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 AL8807 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 AL8807 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 0.4V or lower at CTRL switches off the output MOSFET simplifying PWM dimming.

and SET input pins. Dimming is achieved

IN

Features

 LED Driving Current up to 1.3A (MSOP-8EP)  Better Than 5% Accuracy  High Efficiency up to 96%  Optimally Controlled Switching Speeds  Operating Input Voltage from 6V to 36V  PWM/DC Input for Dimming Control  Built-In Output Open-Circuit Protection  SOT25, MSOP-8EP: Available in “Green” Molding Compound

(No Br, Sb)

 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/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.

Pin Assignments

SW

GND

CTRL

SET GND GND

CTRL

Applications

 MR16 Lamps  General Illumination Lamps  12V Powered LED Lamps  24V Powered LED Lamps

(Top View)

SOT25

(Top View)

MSOP-8EP

V

IN

SET

V N/C SW SW

IN

Typical Applications Circuit

IN

CTRL

D1

DFLS2100

R1

0R15

SET

SW

GND

AL8807

U1

L1

33µH

C4

1µF

NODE

CATHODE

March 2013



D3

DFLS 2100

P1

P2

D4

DFLS2100

AL8807

Document number: DS35281 Rev. 5 - 2

GND

DFLS2100

100nFC5

DFLS 2100

D5

D2

C2

150µF

C3

150µF

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C1

100 nF

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L8807

Pin Descriptions

Pin Name

Pin Number

SOT25 MSOP-8EP

Function

SW 1 5, 6 Switch Pin. Connect inductor/freewheeling diode here, minimizing track length at this pin to reduce EMI.

GND 2 2, 3 GND Pin

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

(V

= V

CTRL 3 4

CTRL

= 2.5V giving nominal average output current I

REF

 Drive to voltage below 0.4V to turn off output current  Drive with DC voltage (0.5V < V

< 2.5V) to adjust output current from 20% to 100% of I

CTRL

OUTnom

= 0.1/RS)

OUTnom

 A PWM signal (low level ≤ 0.4V and high level > 2.6; transition times less than 1us) allows the output

current to be adjusted below the level set by the resistor connected to SET input pin.

SET 4 1 Set Nominal Output Current Pin. Configure the output current of the device.

VIN

5 8

EP — EP

Input Supply Pin. Must be locally decoupled to GND with > section for more information.

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

2.2µF X7R ceramic capacitor – see applications

N/C — 7 No Connection

Absolute Maximum Ratings (@T

= +25°C, unless otherwise specified.)

A

Symbol Parameter Ratings Unit

ESD HBM Human Body Model ESD Protection 2.5 kV

ESD MM Machine Model ESD Protection 200 V

VIN Continuous VIN Pin Voltage Relative to GND

VSW

V

CTRL

I

SW-RMS

I

SW-PK

TJ

T

LEAD

TST

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.

SW Voltage Relative to GND -0.3 to +40 V CTRL Pin Input Voltage -0.3 to +6 V

DC or RMS Switch Current Peak Switch Current (<10%) 2.5 A

SOT25 1.25 MSOP-8EP 1.6

Junction Temperature 150 °C Lead Temperature Soldering 300 °C Storage Temperature Range -65 to +150 °C

-0.3 to +40 V

A

Recommended Operating Conditions (@T

= +25°C, unless otherwise specified.)

A

Symbol Parameter Min Max Unit

VIN

V

CTRLH

V

CTRLDC

V

CTRLL

fSW ISW

TJ

Operating Input Voltage Relative to GND 6.0 36 V Voltage High for PWM Dimming Relative to GND 2.6 5.5 V Voltage Range for 20% to 100% DC Dimming Relative to GND 0.5 2.5 V Voltage Low for PWM Dimming Relative to GND 0 0.4 V Maximum Switching Frequency 1 MHz

Continuous Switch Current

SOT25 1 MSOP-8EP 1.3

Junction Temperature Range -40 +125 °C

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AL8807

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L8807

Electrical Characteristics (@V

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

IN

Symbol Parameter Conditions Min Typ Max Unit

V

INSU

V

INSH

VTH

V

TH-H

I

SET

R

CTRL

V

R

DS(on)

I

SW_Leakage







Notes: 4. AL8807 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 35 for the device derating curve.

6. Test condition for SOT25: Device mounted on FR-4 PCB (25mm x 25mm 1oz 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.

7. 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

8. Dominant conduction path via Gnd pin (pin 2).

9. Dominant conduction path via exposed pad.

Internal Regulator Start-Up Threshold Internal Regulator Hysteresis Threshold Quiescent Current Output not switching (Note 4) 350 µA

IQ

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

IS

VIN rising VIN falling

Set current Threshold Voltage 95 100 105 mV Set Threshold Hysteresis ±20 mV SET Pin Input Current CTRL Pin Input Resistance Referred to internal reference 50 kΩ Internal Reference Voltage 2.5 V

REF

On Resistance of SW MOSFET SW Rise Time

tR

SW Fall Time 20 ns

tF

Switch Leakage Current Thermal Resistance Junction-to-Ambient (Note 5)

JA

Thermal Resistance Junction-to-Lead (Note 8) SOT25 (Note 6) 50

JL

Thermal Resistance Junction-to-case (Note 9) MSOP-8EP (Note 7) 4.3

JC

≤ 2.5V

CTRL

V

= VIN-0.1

SET

ISW = 1A

= 100±20mV, fSW = 250kHz

V

SENSE

V

= 0.1V to 12V to 0.1V, CL = 15pF

SW

VIN =30V SOT25 (Note 6) 250 MSOP-8EP (Note 7) 69

5.9 V

100 300 mV

16 22 µA

0.25 0.4 Ω 12 ns

0.5 μA

C/W

= 0V. Parameter is

SENSE

AL8807

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F

REQ

UENCY

H

CUR

REN

T

Typical Performance Characteristics

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

100

90

V = 0V

CTRL

V = V

SET IN

T = 25°C

A

L8807

900 800

L = 33µH

700

z)

600

(k

L = 68µH

500 400 300 200

L = 100µH

100

0

01234

V

CTRL

Figur e 2. Switch i ng Frequ ency vs. V

80

V = V = 12V

SET IN

60

T = 25°C

A

V = 12V

IN

1 LED R = 150m

SET

T = 25°C

A

CTRL



5

70

40

(A)

60

40

LED

30

20

0

0.0 0.5 1.0 1.5 2.0 3.0 3.5 4.0 4.5 5.0 5.5

2.5

CTRL PIN VOLT AGE (V)

Figure 3. LED Current vs. V

CTRL

3

2.5

20

CTRL

0

I (µA)

-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 4. I vs . V

CTRL

CTRL CTRL

2.52

V = Open

CTRL

V = V= 12V

SET IN

2.51

2

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 5. V vs. Input Voltage

15 33

V (V)

IN

CTRL

V = V

SET IN

T = 25°C

A

2.49

2.48

-40 -15 10 35 60 85 110 AMBIENT TEMPERATURE (°C)

Figure 6. V VS. TEMPERATURE

CTRL

(CTRL Pin Open Circuit)

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A

R

UTY CYC

Typical Performance Characteristics (cont.)

9

L = 68H, R = 150m

S

T = 25C, V = 12V

AIN

8

CTRL = PWM, f = 500Hz 1 LED

7 6

LED Current Error

5 4

PWM

LED Current

3 2

LED CURRENT ERROR (%)

1 0

020406080100

0.8

0.7

0.6

0.5

0.4

0.3

0.2

0.1 0

PWM DUTY CYCLE

Figure 7. I vs. PWM Duty Cycle

LED

L8807

300 270

240 210



180

(m )

150

DS(ON)

120

LED CURRENT (A)

90 60 30

0

6 9 12 18 21 24 27 30 36

Figure 8. SW R vs. Input Voltage

15 33

V (V)

IN

DS(ON)

V = Open

CTRL

V = V

SET IN

T = 25°C

A

400

350

300



(m )

250

DS(ON)

200

150

100

-40 -15 35 60 11010 85 Ambie nt Temperature ( C)

Figure 9. SW R vs. Tempera ture

DS(ON)

V = Open

CTRL

V = V= 12V

SET IN



100

90 80

3 LEDS

L = 68µH R = 100m

T = 25°C V = Open

S A CTRL



70

2 LEDS

60

LE (%)

50 40

D

30 20 10

0

6 9 12 15 18 21 24 27 30 33 36

INPUT VOLTAGE (V)

Figure 10. Duty Cycle vs. Input Voltage

Figure. 11 SW Output Rise Time

Figure. 12 SW Output Fall Time

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C

URRENT ERRO

R

TCHING F

R

Q

UENC

Y

H

CUR

RENT ERRO

R

TCHING F

REQ

UENC

Y

H

CUR

R

T ERRO

R

T

C

H

G

F

R

Q

U

C

Y

H

Typical Performance Characteristics (cont.) (670LED Current)

10

8 6

(%)

4 2 0

-2

-4

-6

LED

-8

-10 6 9 12 15 18 21 24 27 30 33 36

INPUT VOLTAGE (V)

Figure 13. LED Curren t Deviation vs . Input V ol t age

z) (k

E

SWI

350

300

250

200

150

100

50

0

6 9 12 15 18 21 24 27 30 33 36

INPUT VOLTAGE (V)

Figure 1 4. Sw i t ching Freque ncy vs. Input Voltage

L8807

10

8 6

(%)

4 2 0

-2

-4

-6

LED

-8

-10 6 9 12 15 18 21 24 27 30 33 36

INPUT VOLTAGE (V)

Figure 15. LED Curren t Deviation vs . Input V ol t age

10

L = 33µH R = 150m



S

T = 25°C

A

V = Open

CTRL

1 LED

(%)

8 6

4

2 LEDs

2

500 450

z)

400

(k

350 300 250

200 150

100

SWI

50

0

6 9 12 15 18 21 24 27 30 33 36

INPUT VOLTAGE (V)

Figure 1 6. Sw itching Freq uency vs. Input Vol t age

800

L = 33µH



R = 150m

S

700

T = 25°C

600

500

A

V = Open

CTRL

z) (k

EN

0

EN

LED

3 LEDs

-2

-4

-6

4 LEDs

5 LEDs

6 LEDs

7 LEDs

8 LEDs

-8

-10 6 9 12 15 18 21 24 27 30 33 36

INPUT VOLTAGE (V)

Figure 17. LED Current Deviation vs. Input Voltage

E

400 300

1 LED

IN

200

4 LEDs

5 LEDs

6 LEDs

SWI

100

3 LEDs

2 LEDs

0

6 9 12 15 18 21 24 27 30 33 36

7 LEDs

8 LEDs

INPUT VOLTAGE (V)

Figure 18. Switching Frequency vs. Input Voltage

AL8807

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