Diodes AL5801 User Manual

A

L5801

100V, ADJUSTABLE CURRENT SINK LINEAR LED DRIVER

EXT

Pin Assignments

Applications

• Linear LED Drivers

• LED Signs

• Offline LED Luminaries

(Top View)

SOT26

Description

The AL5801 combines a 100V N-channel MOSFET with a prebiased NPN transistor to make a simple, small footprint LED driver.

The LED current is set by an external resistor connected from R pin (4) to GND pin (6). The internal pre-biased transistor develops approximately 0.56V across the external resistor.

The AL5801 open-drain output can operate from 1.1V to 100V enabling it to operate 5V to 100V power supplies without additional components.

PWM dimming of the LED current can be achieved by driving the BIAS pin (1) with an external, open-collector NPN transistor or open-drain N-channel MOSFET.

The AL5801 is available in a SOT26 package and is ideal for driving LED currents up to 350mA.

Features

• Feedback Pin Reference Voltage V

• -40°C to +125°C Temperature Range

• 1.1V to 100V Open-Drain Output

• Negative temperature V

the LED current at high temperatures

• Low thermal impedance SOT26 package with copper lead frame

• Lead-Free Finish; RoHS Compliant (Notes 1 & 2)

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

• Qualified to AEC-Q101 Standards for High Reliability

Notes: 1. EU Directive 2002/95/EC (RoHS) & 2011/65/EU (RoHS 2) compliant. All applicable RoHS exemptions applied.

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.

co-efficient automatically reduces

RSET

= 0.56V at +25°C

RSET

Typical Applications Circuit

AL5801

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Pin Descriptions

Number

1 BIAS Biases the open-Drain output MOSFET 2 FB Feedback pin 3 OUT Open-Drain LED driver output 4 R

5 COMP 6 GND Ground refe rence point for setting the LED current

Name

Current sense pin. LED current sensing resistor should be connected from here to GND

EXT

Compensation pin. Connect COMP pin to REXT pin and insert a 1nF ceramic capacitor from COMP pin to FB pin for improved transient stability

Functional Block Diagram

L5801

Function

Figure 1 Block Diagram

Absolute Maximum Ratings (@T

Symbol Characteristics Values Unit

V

OUT

V

BIAS

VFB

V

COMP

V

REXT

I

OUT

TJ

TST

Note: 4. With pins 5 and 6 connected together.

These are stress ratings only. Operation outside the absolute maximum ratings may cause device failure. Operation at the absolute maximum rating for extended periods may reduce device reliability.

Output voltage relative to GND 100 V BIAS voltage relative to GND (Note 4) 20 V FB voltage relative to GND 6 V COMP voltage relative to GND 6 V REXT voltage relative to GND 6 V Output current 350 mA Operating junction temperature -40 to +150 °C Storage temperature -55 to +150 °C

= +25°C, unless otherwise specified.)

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AL5801

Document number: DS35555 Rev. 3 - 2

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L5801

Package Thermal Data

Characteristic Symbol Value Unit

Power Dissipation (Note 5) @ TA = +25°C Power Dissipation (Note 6) @ TA = +25°C Power Dissipation (Note 7) @ TA = +25°C Power Dissipation (Note 8) @ TA = +25°C Thermal Resistance, Junction to Ambient Air (Note 5) @ TA = +25°C Thermal Resistance, Junction to Ambient Air (Note 6) @ TA = +25°C Thermal Resistance, Junction to Ambient Air (Note 7) @ TA = +25°C Thermal Resistance, Junction to Ambient Air (Note 8) @ TA = +25°C

Notes: 5. Device mounted on 15mm x 15mm 2oz copper board.

6. Device mounted on 25mm x 25mm 1oz copper board.

7. Device mounted on 25mm x 25mm 2oz copper board.

8. Device mounted on 50mm x 50mm 2oz copper board.

P

D

R

JA

θ

0.75

0.70

0.85

1.05 165 180 145 120

W

°C/W

Recommended Operating Conditions (@T

= +25°C, unless otherwise specified.)

A

Symbol Parameter Min Max Unit

V

BIAS

V

OUT

I

LED

TA

Note: 9. Subject to ambient temperature, power dissipation and PCB.

NMOSFET Electrical Characteristics: (Q1) (@T

OFF CHARACTERISTICS

Drain-Source Breakdown Voltage Zero Gate Voltage Drain Current Gate-Source Leakage

ON CHARACTERISTICS

Gate Threshold Voltage Static Drain-Source On-Resistance Forward Transconductance

Diode Forward Voltage

DYNAMIC CHARACTERISTICS

Input Capacitance Output Capacitance Reverse Transfer Capacitance

AL5801

Document number: DS35555 Rev. 3 - 2

Supply voltage range 3.5 20 OUT voltage range 1.1 100

V

LED pin current (Note 9) 25 350 mA Operating ambient temperature range -40 125 °C

= +25°C, unless otherwise specified.)

A

Characteristic Symbol Min Typ Max Unit Test Condition

BV

DSS

I

DSS

I

⎯ ⎯

GSS

V

GS(th)

R

⎯

DS (ON)

g

⎯

fs

V

SD

C

⎯

iss

C

⎯

oss

C

rss

100

⎯ ⎯

2.0

⎯

0.89 1.1 V

⎯

⎯ ⎯

±100

⎯

0.85

0.99

0.9

129

14

8

1 µA

4.1 V

⎯

⎯ ⎯ ⎯

V

GS

V

DS

nA

V

GS

V

DS

V

GS

Ω

V

GS

S

V

DS

VGS = 0V, IS = 1.5A

pF

V

pF pF

DS

f = 1.0MHz

= 0V, ID = 250µA = 60V, VGS = 0V

= ±20V, VDS = 0V

= VGS, ID = 250µA

= 10V, ID = 1.5A = 6V, ID = 1A

= 15V, ID = 1A

= 50V, VGS = 0V

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A

M

A

P

OWER D

PATIO

N

M

P

OWER D

PATIO

N

U

NCTIO

N T

O

N

T

R

Pre-Bias Transistor Electrical Characteristics: (Q2) (@T

Characteristic (Note 10) Symbol Min Typ Max Unit Test Condition

V

Input Voltage Output Voltage

Output Current DC Current Gain Input Resistance Resistance Ratio

Notes: 10. Short duration pulse test used to minimize self-heating effect.

V

I

R

I(off) I(on)

O(on)

O(off)

G

R

1

2/R1

1

0.4 - - V

- - 1.5 V

- 0.05 0.3 V

- - 0.5

80 - - -

3.2 4.7 6.2 kΩ 8 10 12 - -

Thermal Characteristics

1.2

= +25°C, unless otherwise specified.)

A

VCC = 5V, IO = 100μA VCC = 0.3V, IO = 5mA IO/II = 5mA/0.25mA

μA

VCC = 50V, VI = 0V VO = 5V, IO = 10mA

L5801

1.0

(W)

ISSI

0.8

0.6

50mm x 50mm

(2oz. FR4)

25mm x 25mm

(2oz. FR4)

15mm x 15mm

(2oz. FR4)

0.4

X

0.2

0

0 25 50 75 100 125 150

TEMPERATURE (°C)

Figur e 2 Derating Cur ve

180 160

140

T = 25°C

A

25mm x 25mm 1oz. FR4

AI

120

100

AMBIE

D = 0.5

80

60

D = 0.2

T = 25°C

A

2oz. FR4

1.0

(W)

0.8

ISSI

0.6

0.4

AX

0.2

0

0 500 1,000 1,500 2,000 2,500

COPPER AREA (mm )

D = 0.1

D = 0.05

Figur e 3 Area vs. Max Power

2

J

40

THERMAL RESISTANCE (°C/W)

Single Pulse

20

0

0.0001 0.001 0.01 0.1 1 10 100 1,000 PULSE WIDTH (s)

Figure 4 Tran si ent Therm al Impedance

AL5801

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Typical Performance Characteristics

0.40

0.35

0.30

I = 0.1mA

bias

R = 1.6

Ω

EXT

L5801

400 350

300

I = 0.1mA

bias

0.25

0.20

OUT

I (A)

0.15

R = 3.75

EXT

Ω

0.10

0.05 0

0123

Figure 5 Output Current vs. V

R = 11.6

EXT

R = 22.7

EXT

V (V)

OUT

Ω

OUT

0.5

T = -40C

°

0.4

A

T = 25C

°

A

0.3

T = 85C

°

OUT

I (A)

0.2

0.1

0

0123

V (V)

OUT

Figure 7 Output Current vs. V

A

I = 0.1mA

bias

R = 1.6

Ω

EXT

OUT

0.07

250

200

OUT

I (mA)

150

100

50

0

110100

Figure 6 Output Current vs. R

Ω

R ()

EXT

0.20

T = -40C

°

A

0.15

0.10

OUT

I (A)

T = 25C

°

A

T = 85C

°

A

0.05

I = 0.1mA

bias

EXT

Ω

OUT

R = 3.75

0

0246810

V (V)

OUT

Figure 8 Output Current vs. V

0.035

0.06

0.05

0.04

OUT

0.03

I (A)

0.02

0.01

0

0 5 10 15

Figure 9 Output Current vs. V

AL5801

Document number: DS35555 Rev. 3 - 2

T = -40C

A

T = 25C

A

T = 85C

A

V (V)

OUT

°

I = 0.1mA

bias

R = 11.6

EXT

Ω

OUT

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OUT

I (A)

0.030

0.025

T = -40C

A

T = 25C

A

0.020

T = 85C

A

0.015

0.010

I = 0.1mA

0.005

0

0 5 10 15 20

V (V)

OUT

bias

R = 22.7

EXT

Figure 10 Output Current vs. V

°

Ω

OUT

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Typical Performance Characteristics (cont.)

800 700

600

400 350

300

50mm x 50mm

(2oz. FR4)

L5801

I = 0.1mA

bias

T = 85°C

A

500

400

REXT

V (mV)

300

200

100

0

-50 0 50 100 150

JUNCTION TEMPERATURE ( C)

Figure 11 V vs. Junction Temperature

REXT

AL5801

Document number: DS35555 Rev. 3 - 2

I = 0.1mA

bias

= 5V

V

bias

°

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25mm x 25mm

(2oz. FR4)

15mm x 15mm

(2oz. FR4)

OUT

I (mA)

250

200

150

100

50

0

110100

Figure 12 Output Current vs. V

V (V)

OUT

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Application Information

L5801

Figure 13 Typical Application Circuit for

Linear Mode Current Sink LED Driver

The AL5801 is designed for driving high brightness LEDs with typical LED current up to 350mA. It provides a more cost effective way for driving low current LEDs when compared against more complex switching regulator solutions. Furthermore, it reduces the PCB board area of the solution because there is no need for external components like inductors, capacitors and/or switching diodes.

Figure 13 shows a typical application circuit diagram for driving an LED or a string of LEDs. The NPN transistor Q2 measures the LED current by sensing the voltage across an external resistor R

. Q2 uses its VBE as reference to set the voltage across R

EXT

and controls the gate voltage of

EXT

MOSFET Q1. Q1 operates in linear mode to regulate the LED current. The LED current is:

= V

/ R

EXT

where V

is the VBE of Q2. VBE is 0.56V typical at a +25°C device temperature. See Figure 11 for the variation of VBE with Q2’s junc tion

RSET

temperature at I

I

LED

RSET

= 0.1mA. VBE has a negative temperature coefficient which reduces the LED current as the device warms up, protecting the

BIAS

LED(s). R

should be chosen to drive 0.1mA current into the BIAS pin

BIAS

R

= ( VCC – 3.75V ) / 0.1mA

BIAS

From the above equation, for any required LED current the necessary external resistor R

R

= V

/ I

EXT

RSET

LED

can be calculated from

EXT

The expected linear mode power dissipation must be factored into the design consideration. The power dissipation across the dev ice can be calculated by taking the maximum supply voltage less the minimum voltage across the LED string.

V

DS(Q1)

= V

CC(max)

– V

LED(min)

– V

RSET

= V

P

D

DS(Q1)

* I

LED

As the output LED current of AL5801 increases so will its power dissipation. The power dissipation will cause the device temperature to rise above ambient, T

, by an amount determined by the package thermal resistance, R

A

θJA

.

Therefore, the power dissipation supported by the device is dependent upon the PCB board material, the copper area and the ambient temperature. The maximum dissipation the device can handle is given by:

P

= ( T

D

= +150°C is the maximum device junction temperature. Refer to the thermal characteristic graphs in Figure 2 to 4 for selecting the

T

J(MAX)

- TA ) / R

θJA

appropriate PCB copper area. Figure 12 shows the current capabilities of the AL5801 at +25°C with different PCB copper area heat sinks.

AL5801

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L5801

Constant LED Current Temperture Compensation

Variation in the junction temperature of Q2 will cause variations in the value of controlled LED current I decreases with increasing temperature at a rate of approximately 2mV/°C. Figure 14 shows a simple temperature compensation network, which comprises of an NTC thermistor and resistor R

, for stabilizing the LED current.

base

. The base-emitter VBE voltage of Q2

LED

Figure 14 Constant LED Current Temperature Compensation for AL5801

The voltage drop V

is 0.56V at room temperature with 0.1mA I

V

BE(Q2)

With the V

chosen, the sense resistor value for 350mA I

RSET

= V

R

EXT

So a standard resistor value of 1.78Ω with 1% tolerance is used.

The R

resistance of the NTC thermistor at room temperature is recommended as 10kΩ. The value of base resistor R

TH

Q2’s base current is obtained as

I

B(Q2)

When V

is changed to V

BE(Q2)

given by

T

R

= V

TH

At -2mV/°C, V

BE(Q2)

resistance at +85°C to keep the same output current is given by

85

R

TH

The NTC thermistor is chosen for compensation whose resistance is 10kΩ at +25°C and 1.38kΩ at +85°C with a β value of 3530. Figure 15 shows the I

in the sense resistor R

RSET

/ I

RSET

LED

= ( V

BE

RSET

T

/ (( V

- V

RSET

= 0.62V / 350mA = 1.77Ω

)

/ R

BE(Q2)

BE

base

T

as the temperature increases to TºC, the thermistor resistance at T°C required to compensate this variation is

T

- V

) / R

BE

should be set to be 40 to 100mV higher than the V

EXT

- V

base

, so V

BIAS

/ RTH = ( 0.62V - 0.56 ) / 470Ω - 0.56V / 10kΩ = 72µA

BE(Q2)

- I

)

B(Q2)

is selected to be 0.62V.

RSET

is determined by

LED

at 25ºC. Figure 11 shows the typical

BE(Q2)

is set to be 470Ω.

base

reduces to 0.44V from 0.56V as the temperature increases from +25°C to +85°C. From the above equation, the thermistor’s

= 0.44V / (( 0.62V – 0.44V ) / 470Ω - 72µA ) = 1.4kΩ

variation with temperature with and without temperature compensation.

LED

AL5801

Document number: DS35555 Rev. 3 - 2

Figure 15 LED Current Variation with and

without Temperature Compensation

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PWM Dimming

L5801

(a)

Figure 16 Application Circuits for LED Driver with PWM Dimming Functionality (a) MOSFET driving and (b) Transistor driving

PWM dimming can be achieved by driving the BIAS pin (1). An external open-collector NPN transistor or open-dr ain N-channel M OSFET can b e used to drive the BIAS pin as shown in Figure 16. Dimming is achieved by turning the LEDs ON and OFF for a portion of a single cycle. The PWM signal can be provided by a micro-controller or by analog circuitry.

Figure 17 shows the LED current against the PWM signal duty ratio when the AL5801 is used to drive three series connected LEDs from a 12V supply. The PWM dimming frequency is set to 200Hz. The PWM signal is supplied to the open-Drain small signal MOSFET’s gate as shown in Figure 16a. The BIAS pin signal is an inversion of the PWM drive to the MOSFET’s gate. Therefore, a PWM signal d ut y cycle of 0% provides the maximum LED current. Sufficiently large PCB copper area is used for heat sinking of the AL5801 in order to minimize the device self-heating at +25°C ambient.

(b)

Figure 17 LED Current against PWM Dimming Signal Duty Ratio at 200Hz PWM Frequency

AL5801

Document number: DS35555 Rev. 3 - 2

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Ordering Information

Part Number Qualification



Green



Green

AL5801W6-7 Commercial W6 SOT26 3,000/Tape & Reel -7

AL5801W6Q-7 Automotive W6 SOT26 3,000/Tape & Reel -7

Notes: 11. For packaging details, go to our website at http://www.diodes.com

Package

Code

Packaging

(Note 11)

Quantity Part Number Suffix

7” Tape and Reel

Marking Information

L100 = Product Type Marking Code YM = Date Code Marking Y = Year (ex: Y = 2012) M = Month (ex: 9 = September)

Date Code Key

Year 2012 2013 2014 2015 2016 2017 2018

Code Z A B C D E F

Month Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

Code 1 2 3 4 5 6 7 8 9 O N D

Package Outline Dimensions (All dimensions in mm.)

A

B C

K

H

J

D

L

SOT26

Dim Min Max Typ

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

⎯ ⎯

0.95

H 2.90 3.10 3.00

J 0.013 0.10 0.05

K 1.00 1.30 1.10

M

L 0.35 0.55 0.40

M 0.10 0.20 0.15

0° 8°

α

⎯

All Dimensions in mm

Suggested Pad Layout

G

Z

Y

C2

C1

Dimensions Value (in mm)

Z G X Y

C1 2.40

C2

3.20

1.60

0.55

0.80

0.95

X

AL5801

Document number: DS35555 Rev. 3 - 2

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L5801

July 2012

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L5801

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 application or use of this document or any product described herein; neither does Diodes Incorporated convey any license under its patent or trademark rights, nor the rights of others. Any Customer or user of this document or products described herein in such applications shall assume all risks of such use and will agree to hold Diodes Incorporated and all the companies whose products are represented on Diodes Incorporated website, harmless against all damages.

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 hold Diodes Incorporated and its representatives harmless against all claims, damages, expenses, and attorney fees arising out of, directly or indirectly, any claim of personal injury or death associated with such unintended or unauthorized application.

Products described herein may be covered by one or more United States, international or foreign patents pending. Product names and markings noted herein may also be covered by one or more United States, international or foreign trademarks.

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.

www.diodes.com

IMPORTANT NOTICE

LIFE SUPPORT

AL5801

Document number: DS35555 Rev. 3 - 2

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