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

© Diodes Incorporated

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)

AL8807

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R

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

AL8807

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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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C

URRENT ERRO

R

TCHING FREQ

UENC

Y

H

CUR

RENT ERRO

R

TCHIN

G FREQ

UENCY

H

CUR

R

T

R

ROR

T

C

HIN

G

R

Q

UENCY

H

L8807

Typical Performance Characteristics (cont.) (1A LED Current MSOP-8EP)

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 19. LED Curren t Deviation vs . Input V ol t age

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 21. LED Curren t Deviation vs . Input V ol t age

10

8
6

(%)

4
2

E

0

EN

-2

-4

-6

LED

-8

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

INPUT VOLTAGE (V)

Figure 23. LED Curren t Deviation vs . Input V ol t age

AL8807

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350

L = 100µH
R = 100m



S

300

z)

T = 25°C

A

V = Open

(k

CTRL

250

200

150

1 LED

100

50

SWI

4 LEDs

2 LEDs

3 LEDs

0

6 9 12 15 18 21 24 27 30 33 36

5 LEDs

6 LEDs

7 LEDs

8 LEDs

INPUT VOLTAGE (V)

Figure 20. Switching Frequency vs. Input Voltage

350

300

z)
(k

250

200

150

100

50

SWI

0

6 9 12 15 18 21 24 27 30 33 36

INPUT VOLTAGE (V)

Figure 22. Switching Frequency vs. Input Voltage

600

z)

500

(k

400

E

300

F

200

100

SWI

0

6 9 12 15 18 21 24 27 30 33 36

INPUT VOLTAGE (V)

Figure 24. Switching Fr equency vs. In put Vol t age

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CUR

RENT ERRO

R

TCHING F

REQ

UENC

Y

H

CUR

RENT ERRO

R

TCHING F

REQ

UENC

Y

H

CUR

R

T ER

ROR

T

C

H

N

G F

R

Q

U

NCY

H

Typical Performance Characteristics (cont.) (1.3A LED Current MSOP-8EP)

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 25. LED Curren t Deviation vs . Input V ol t age

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 27. LED Curren t Deviation vs . Input V ol t age

250

L = 100µH
R = 77m

200

S

T = 25°C

A

V = Open

CTRL

z)
(k

150

100

1 LED

50

SWI

3 LEDs

2 LEDs

0

6 9 12 15 18 21 24 27 30 33 36

Figure 2 6. Switching Fre quency vs. Inpu t Voltage

300

L = 68µH
R = 77m

S

T = 25°C

z)

250

A

V = Open

(k

CTRL

200

150

100

1 LED

50

SWI

2 LEDs

3 LEDs

0

6 9 12 15 18 21 24 27 30 33 36

Figure 28. Switching Frequency vs. Input Voltage



5 LEDs

4 LEDs

6 LEDs

INPUT VOLTAGE (V)



4 LEDs

5 LEDs

6 LEDs

INPUT VOLTAGE (V)

7 LEDs

7 LEDs

L8807

8 LEDs

8 LEDs

10

8
6

(%)

4
2
0

EN

-2

-4

-6

LED

-8

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

INPUT VOLTAGE (V)

Figure 29. LED Curren t Deviation vs . Input V ol t age

600

L = 33µH



R = 77m

500

S

T = 25°C

A

V = Open

CTRL

z)
(k

400

E

300

E

200

I

1 LED

100

SWI

2 LEDs3 LEDs

0

6 9 12 15 18 21 24 27 30 33 36

4 LEDs

5 LEDs

6 LEDs

7 LEDs

8 LEDs

INPUT VOLTAGE (V)

Figure 30. Switching Frequency vs. Input Voltage

AL8807

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L8807

Application Information

The AL8807 is a hysteretic (also known as equal ripple) LED driver with integrated power switch. It is available in two packages that provide a PCB
area-power dissipation capability compromise. It is recommended that at higher LED currents/smaller PCBs that the MSOP-8EP version is used to
maximize the allowable LED current over a wider ambient temperature range.

AL8807 Operation

In normal operation, when voltage is applied at +VIN, the AL8807 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.

This rising current produces a voltage ramp across R
voltage to the input of the internal comparator.

When this voltage reaches an internally set upper threshold, the internal switch is turned off. The inductor current continues to flow through R
the LEDs and the schottky diode D1, and back to the supply rail, but it decays, with the rate of decay determined by the forward voltage drop of the
LEDs and the schottky diode.

This decaying current produces a falling voltage at R
applied at the input of the internal comparator. When this voltage falls to the internally set lower threshold, the internal switch is turned on again.

This switch-on-and-off cycle continues to provide the average LED current set by the sense resistor R

LED Current Control

The LED current is controlled by the resistor R1 in Figure 30.

. The internal circuit of the AL8807 senses the voltage across R1 and applies a proportional

1

, L1,

1

, which is sensed by the AL8807. A voltage proportional to the sense voltage across R1 is

1

.

1

Figure 30 Typical Application Circuit

Connected between V

I

LED

For example for a desired LED current of 660mA and a default voltage V

1R

and SET the nominal average output current in the LED(s) is defined as:

IN

V

THD



V

I

LED

THD

1R

1.0

66.0

 m150

=2.5V the resulting resistor is:

CTRL

DC Dimming

Further control of the LED current can be achieved by driving the CTRL pin with an external voltage (between 0.4V and 2.5V); the average LE D
current becomes:

V

V

CTRL

THD

I 

LED

V

REF

With 0.5V ≤ V
be clamped to approximately 100% and follows

When the CTRL voltage falls below the threshold, 0.4V, the output switch is turned off which allows PWM dimming.

≤ 2.5V the LED current varies linearly with V

CTRL

AL8807

Document number: DS35281 Rev. 5 - 2

R

SET

, as in figure 2. If the CTRL pin is brought higher than 2.5V, the LED current will

CTRL

V

I 

LED

THD

.

R

SET

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]

L8807

Application Information (cont.)

PWM Dimming

LED current can be adjusted digitally, by applying a low frequency Pulse Width Modulated (PWM) logic signal to the CTRL pin to t urn the device o n
and off. This will produce an average output current proportional to the duty cycle of the control signal. In particular, a PWM signal with a max
resolution of 10bit can be applied to the CTRL pin to change the output current to a v alue belo w the nominal average value set by resistor R
achieve this resolution the PWM frequency has to be lower than 500Hz, however higher dimming frequencies can be used, at the expense of
dimming dynamic range and accuracy.

Typically, for a PWM frequency of 500Hz the accuracy is better than 1% for PWM ranging from 1% to 100%.

700

600

500

400

SET

. To

300

200

LED current [mA

100

0

0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%

Zooming in at duty cycles below 10% shows:

PW M d im m in g [%]

Figure 31 PWM Dimming at 500Hz

Figure 32 Low Duty Cycle PWM Dimming at 300Hz

The accuracy of the low duty cycle dimming is affected by both the PWM frequency and also the switching frequency of the AL8807. For best
accuracy/resolution the switching frequency should be increased while the PWM frequency should be reduced.

The CTRL pin is designed to be driven by both 3.3V and 5V logic levels directly from a logic output with either an open drain output or push pull
output stage.

AL8807

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Application Information (cont.)

Soft Start

The AL8807 does not have in-built soft-start action – this provides very fast turn off of the output the stage improving PWM dimming accuracy;
nonetheless, adding an external capacitor from the CTRL pin to ground will provide a soft-start delay. This is achieved by increasing the time taken
for the CTRL voltage to rise to the turn-on threshold and by slowing down the rate of rise of the control voltage at the input of the comparator.

Adding a capacitor increases the time taken for the output to reach 90% of its final value, this delay is 0.1ms/nF, but will impact on the PWM
dimming accuracy depending on the delay introduced.

Figure 33 Soft start with 22nF capacitor on CTRL pin (V

= 30V, I

IN

= 667mA, 1 LED)

LED

Reducing Output Ripple

Peak to peak ripple current in the LED(s) can be reduced, if required, by shunting a capacitor C2 a cross the LED(s) as shown al ready in the circuit
schematic.

A value of 1μF will reduce the supply ripple current by a factor three (approx.). Proportionally lo wer ripple can be achieved with higher capacitor
values. Note that the capacitor will not affect operating frequency or efficiency, but it will increase start-up delay, by reducing the rate of rise of LE D
voltage. By adding this capacitor the current waveform through the LED(s) changes from a triangular ram p to a more sinusoidal version without
altering the mean current value.

Capacitor Selection

The small size of ceramic capacitors makes them ideal for AL8807 applications. X5R and X7R types are recommended because they retain their
capacitance over wider voltage and temperature ranges than other types such as Z5U.

A 2.2μF input capacitor is sufficient for most intended applications of AL8807; however a 4.7μF input capacitor is suggested for input voltages
approaching 36V.

AL8807

Document number: DS35281 Rev. 5 - 2

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L8807

Application Information (cont.)

Diode Selection

For maximum efficiency and performance, the rectifier (D1) should be a fast low capacitance Schottky diode with low reverse leakage at the
maximum operating voltage and temperature. The Schottky diode also provides better efficiency than silicon PN diodes, due to a combination of
lower forward voltage and reduced recovery time.

It is important to select parts with a peak current rating above the peak coil current and a continuous current rating higher t h an th e maximum outpu t
load current. In particular, it is recommended to have a diode voltage rating at least 15% higher than the operating voltage to ensure safe operation
during the switching and a current rating at least 10% higher than the average diode current. The power rating is verified by calculating the power
loss through the diode.

Schottky diodes, e.g. B240 or B140, with their low forward voltage drop and fast reverse recovery, are the ideal choice for AL8807 applications.

Inductor Selection

Recommended inductor values for the AL8807 are in the range 33μH to 100μH.

Higher values of inductance are recommended at higher supply voltages in order to minimize errors due to switching delays, which result in
increased ripple and lower efficiency. Higher values of inductance also result in a smaller change in output current over the supply voltage range.

(See graphs).

The inductor should be mounted as close to the device as possible with low resistance/stray inductance connections to the SW pin.

The chosen coil should have a saturation current higher than the peak output current and a continuous curren t rating above the required mean
output current.

Suitable coils for use with the AL8807 are listed in the table below:

Part No.

MSS1038-333 33 0.093 2.3
MSS1038-683 68 0.213 1.5

NPIS64D330MTRF 33 0.124 1.1 NIC www.niccomp.com

The inductor value should be chosen to maintain operating duty cycle and switch 'on'/'off' times over the supply voltage and load current range.

AL8807

Document number: DS35281 Rev. 5 - 2

Figure 34 Inductor value with input voltage and number of LEDs

L

(µH)

DCR

(V)

I

SAT

(A)

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CoilCraft www.coilcraft.com

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Application Information (cont.)

The following equations can be used as a guide, with reference to Figure 1 - Operating waveforms.

Switch ‘On’ time Switch ‘Off’ time

IL

IL



t

ON

Where:
L is the coil inductance (H)

is the coil resistance (Ω)RS is the current sense resistance (Ω)

r

L

is the required LED current (A)

I

avg

ΔI is the coil peak-peak ripple current (A) {Internally set to 0.3 x Iavg}
V

is the supply voltage (V)

IN

is the total LED forward voltage (V)

V

LED

is the switch resistance (Ω) {=0.5Ω nominal}

R

SW

is the diode forward voltage at the required load current (V)

V

D





x

IVV



RrR

SWLSAVGLEDIN

t

OFF



Thermal Considerations

For continuous conduction mode of operation, the absolute maximum junction temperature must not be exceeded. The maximum p o wer dissipation
depends on several factors: the thermal resistance of the IC package 
and ambient temperature.

The maximum power dissipation can be calculated using the following formula:

P

= (T

where
T
T


The recommended maximum operating junction temperature, T
junction to ambient thermal resistance, 



JA

approximately 250°C/W (160°C/W on a four-layer PCB).
The maximum power dissipation at T

P
P

Figure 35, shows the power derating of the AL8807W5 on two (one single-layer and four-layer) different 25x25mm PCB with 1oz copper standing in
still air and the AL8807MP on an FR4 51x51mm PCB with 2oz copper standing in still air.

D(MAX)

is the maximum operating junction temperature,

J(MAX)

is the ambient temperature, and

A

is the junction to ambient thermal resistance.

JA

, is layout dependent and package dependent; the AL8807W5’s JA on a 25x25mm single layer PCB with 1oz copper standing in still air is

= (125°C − 25°C) / (250°C/W) = 0.4W for single-layer PCB

D(MAX)

= (125°C − 25°C) / (160°C/W) = 0.625W for standard four-layer PCB

D(MAX)

J(MAX)

− TA) / 

JA

, is 125°C and so maximum ambient temperature is determined by the AL8807’s

J

and device power dissipation.

JA

= 25°C can be calculated by the following formulas:

A

, PCB layout, airflow surrounding the IC, and difference between junction

JA







x

IVV

rR

LSAVGDLED

L8807

AL8807

Document number: DS35281 Rev. 5 - 2

Figure 35 Derating Curve for Different PCB

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L8807

Application Information (cont.)

EMI and Layout Considerations

The AL8807 is a switching regulator with fast edges and measures small differential voltages; as a result of this care has to be taken with
decoupling and layout of the PCB.To help with these effects the AL8807 has been developed to minimise radiated emissions by controlling the
switching speeds of the internal power MOSFET. The rise and fall times are controlled to get the right compromise between power dissipation due
to switching losses and radiated EMI. The turn-on edge (falling edge) dominates the radiated EMI which is due to an interaction between the
Schottky diode (D1), Switching MOSFET and PCB tracks. After the Schottky diode reverse recovery time of around 5ns has occurred; the falling
edge of the SW pin sees a resonant loop between the Schottky diode capacitance and the track inductance, L

, See figure 36.

TRACK

The tracks from the SW pin to the Anode of the Schottky diode, D1, and then from D1’s cathode to the decoupling capacitors C1 should be as short
as possible. There is an inductance internally in the AL8807 this can be assumed to be around 1nH. For PCB tracks a figure of 0.5nH per mm can
be used to estimate the primary resonant frequency. If the track is capable of handling 1A increasing the thickness will have a minor effect on the
inductance and length will dominate the size of the inductance. The resonant frequency of any oscillation is determined by the combined
inductance in the track and the effective capacitance of the Schottky diode. An example of good layout is shown in figure 37 - the stray track
inductance should be less than 5nH.

AL8807

Document number: DS35281 Rev. 5 - 2

Figure 36 PCB Loop Resonance

Figure 37 Recommended PCB Layout

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L8807

Application Information (cont.)

Recommendations for minimising radiated EMI and other transients and thermal considerations are:

1. The decoupling capacitor (C1) has to be placed as close as possible to the V

2. The freewheeling diode’s (D1) anode, the SW pin and the inductor have to be placed as close as possible to each other to avoid ringing.

3. The Ground return path from C1 must be a low impedance path with the ground plane as large as possible

4. The LED current sense resistor (R1) has to be placed as close as possible to the V

5. The majority of the conducted heat from the AL8807 is through the GND pin 2. A maximum earth plane with thermal vias into a second earth
plane will minimise self-heating

6. To reduce emissions via long leads on the supply input and LEDs low RF impedance capacitors (C2 and C5) shoul d be used at the point the
wires are joined to the PCB

A typical application for the AL8807 is an LED MR16 lamp (schematic shown in Figure 38).

pin and D1 Cathode

IN

and SET pins.

IN

An evaluation board for the AL8807 (named the AL8807EV2) for MR16 is available on request from your local Diodes’ sales representative. This
board follows Diodes’ recommendations for low EMI. Images of the top layer and bottom layers are shown in Figure 39.

AL8807

Document number: DS35281 Rev. 5 - 2

Figure 38 MR16 Circuit Schematic

Figure 39 Recommended MR16 PCB Layout

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Application Information (cont.)

The associated EMI measurements for this board using the AL8807 is shown in figure 40.

L8807

Figure 40 AL8807EV2 Radiated EMI Performance

The EMI performance was measured at 12V
class B used for domestic equipment including lighting. The bottom magenta line is the noise floor of the test chamber. The middle purple line is the
EMI emitted radiation of the AL8807 over 30MHz to 1000MHz. This shows that the AL8807 passes the standard with at least 16dB margin.

MR16 lamps typically operate from 12V

In enclosed lamps such MR16 the ability for the device to operate at high ambient temperatures is critical and figure 41 shows the surface
temperature of the AL8807 on AL8807EV2 in operation under the same conditions as the EMI tests at an free air temperature of 25°C. It is
anticipated that the internal junction temperature is approximately 6°C hotter than the surface temperature.

driving two white LEDs (VF = 3.1V at 660mA) on the AL8807EV2. The red bold line is for EN55022

DC

or 12VAC, using conventional electromagnetic transformers or electronic transformers.

DC

The thermal image shows that components increasing the board temperature are the inductor, Schottky diodes and the AL8807.

An inductor choice of 33µH with saturation current higher than 1.1A, will limit the frequency variation between 180kHz and 400kHz over the whole
input voltage variation (8V to 18V), and therefore represent the best choice for an MR16 solution also taking into account the size constraint of the
lamp.

The AL8807 guarantees high performance levels with both 12V
The efficiency is generally higher than 81% and current regulation is better than 0.1mA/V in for a DC input voltage in the range from 8V to 18V.

AL8807

Document number: DS35281 Rev. 5 - 2

Figure 41 Thermal picture of AL8807EV2 at 12V

and 12VDC power supplies.

AC

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DC

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Ordering Information

L8807

L8807 XX - XX

Package

W5 : SOT25
MP : MSOP-8EP

Packing

7 : 7” Tape & Reel
13 : 13” Tape & Reel

Part Number Status Package Code Packaging

AL8807W5-7 New Product W5 SOT25 3000/Tape & Reel -7

AL8807MP-13 New Product MP MSOP-8EP 2500/Tape & Reel -13

Quantity Part Number Suffix

7” Tape and Reel

Marking Information

(1) SOT25

(Top View)

W

7

4

X

: Identification code

XX

: Year 0~9

Y

W

: Week : A~Z : 1~26 week;

a~z : 27~52 week; z represents
52 and 53 week

X

: A~Z : Internal code

(2) MSOP-8EP

5

Y

XX

1 2 3

Part Number Package Identification Code

AL8807W5-7 SOT25 B6

AL8807

Document number: DS35281 Rev. 5 - 2

Part Number Package

AL8807MP-13 MSOP-8EP

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Package Outline Dimensions (All dimensions in mm.)

Please see AP02002 at http://www.diodes.com/datasheets/ap02002.pdf for latest version.

(1) SOT25

(2) MSOP-8EP

D

K

J

A

B C

H

N

D

L

M

4

°

Detail C

X

1

0

°

a

L

x

y

E

E2

1

e

8Xb

A1

A

D

A3

A2

D1

E3

E1

Gauge Plane
Seating Plane

See Detail C

0.25

4

X

1

0

c

AL8807

Document number: DS35281 Rev. 5 - 2

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Dim Min Max Typ

SOT25

A 0.35 0.50 0.38
B 1.50 1.70 1.60
C 2.70 3.00 2.80
D

 

H 2.90 3.10 3.00
J 0.013 0.10 0.05
K 1.00 1.30 1.10

L 0.35 0.55 0.40
M 0.10 0.20 0.15
N 0.70 0.80 0.75

0° 8°



All Dimensions in mm

MSOP-8EP

Dim Min Max Typ

A - 1.10 ­A1 0.05 0.15 0.10
A2 0.75 0.95 0.86
A3 0.29 0.49 0.39

b 0.22 0.38 0.30

c 0.08 0.23 0.15

D 2.90 3.10 3.00
D1 1.60 2.00 1.80

E 4.70 5.10 4.90
E1 2.90 3.10 3.00
E2 1.30 1.70 1.50
E3 2.85 3.05 2.95

e - - 0.65

L 0.40 0.80 0.60

a 0° 8° 4°

x - - 0.750

y - - 0.750

All Dimensions in mm

0.95



L8807

March 2013

© Diodes Incorporated

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Suggested Pad Layout

Please see AP02001 at http://www.diodes.com/datasheets/ap02001.pdf for the latest version.

(1) SOT25

C2C2

(2) MSOP-8EP

G

Z

Y

AL8807

Document number: DS35281 Rev. 5 - 2

Y2

X

X C

G

X1

C1

Y

Y1

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Dimensions Value (in mm)

Z 3.20
G 1.60
X 0.55

Y 0.80
C1 2.40
C2 0.95

Dimensions

C 0.650
G 0.450
X 0.450

X1 2.000

Y 1.350
Y1 1.700
Y2 5.300

Value

(in mm)

L8807

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L8807

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. Diodes Incorporated does not assume any liability arising out of the
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Diodes Incorporated does not warrant or accept any liability whatsoever in respect of any products purchased through unauthorized sales channel.
Should Customers purchase or use Diodes Incorporated products for any unintended or unauthorize d application, Customers shall indemnify and
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This document is written in English but may be translated into multiple languages for reference. Onl y the English version of this document is the
final and determinative format released by Diodes Incorporated.

Diodes Incorporated products are specifically not authorized for use as critical components in life support devices or systems without the express
written approval of the Chief Executive Officer of Diodes Incorporated. As used herein:

A. Life support devices or systems are devices or systems which:

1. are intended to implant into the body, or

2. support or sustain life and whose failure to perform when properly used in accordance with instructions for use provided in the

labeling can be reasonably expected to result in significant injury to the user.
B. A critical component is any component in a life support device or system whose failure to perform can be reasonably expected to cause the

failure of the life support device or to affect its safety or effectiveness.
Customers represent that they have all necessary expertise in the safety and regulatory ramifications of their life support devices or systems, and

acknowledge and agree that they are solely responsible for all legal, regulatory and safety-related requirements concerning their products and any
use of Diodes Incorporated products in such safety-critical, life support devices or systems, notwithstanding any devices- or systems-related
information or support that may be provided by Diodes Incorporated. Further, Customers must fully indemnify Diodes Incorporated and its
representatives against any damages arising out of the use of Diodes Incorporated products in such safety-critical, life support devices or systems.

Copyright © 2013, Diodes Incorporated

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IMPORTANT NOTICE

LIFE SUPPORT

AL8807

Document number: DS35281 Rev. 5 - 2

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