STMicroelectronics L5970 D, L5973 D LED driver Application note

AN2259

APPLICATION NOTE

High intensity LED driver using the L5970D/L5973D

Introduction

High brightness LEDs are becoming a prominent source of light and often have better efficiency and reliability than conventional light sources. While LEDs can operate from an energy source as simple as a battery and resistor, most applications require an efficient energy source not only for the reduction of losses, but also to maintain the brightness of the LED itself. For applications that are powered from low voltage AC sources typically used in landscape lighting or low voltage DC sources that may be used in automotive applications or to meet safety requirements, high efficiency DC-DC converters configured for constant output current provide a high efficiency driver that can operate over a relatively wide range of input voltages to drive series strings of one to several LEDs

This application note describes a DC-DC converter circuit that can easily be configured to drive

LEDs at several different output currents and can be configured for either AC or DC input. The circuit uses the L5973D monolithic step down converter configured to drive a series string of

LEDs in a constant current mode.

L5970D is a step down monolithic power switching regulator capable of delivering 1A while the

L5973D is able to deliver 2A at output voltages from 1.25V to 35V. Both devices use internal P-

Channel D-MOS transistors (with typical R

DS(on)

of 250m

Ω

) as the switching element to minimize the size of external components. An internal oscillator fixes the switching frequency at 250kHz.

The brightness of the LED (Light Emitting Diode), or light intensity as measured in Lumens, is proportional to the forward current flowing through the LED. Since the forward voltage drop of the LED can vary from device to device it is important to drive the LEDs with a constant current driver to be able to get good matching of the light output, especially when they are located side by side where variations in light intensity are quickly noticed. A typical way to drive LEDs in the constant current mode is to use a DC-DC converter configured to give a constant current output. The circuit shown in

Figure 7.

uses the L5973D in a constant current configuration to drive LEDs

AN2259/1105

Rev 1.0

1/38

www.st.com

38

Figure 1.

Board Layout

AN2259

2/38

5

6

7

3

4

1

2

AN2259

Contents

DESCRIPTION OF BOARD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

INPUT CAPACITOR SELECTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

CURRENT FEEDBACK LOOP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

INDUCTOR SELECTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

BOARD LAYOUT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

REFERENCE DESIGN VERSIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

REVISION HISTORY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36

3/38

AN2259

Figures

Figure 1.

Board Layout . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

Figure 2.

Current feedback . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

Figure 3.

Ripple Current (One 1W LED). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

Figure 4.

Ripple current (One 5W LED) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

Figure 5.

Top side of Board (not in scale) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

Figure 6.

Bottom side of Board (not in scale) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

Figure 7.

Board Schematic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

Figure 8.

12Vac Input 1W LED Driver Schematic . . . . . . . . . . . . . . . . . . . . . . . . . . 18

Figure 9.

12Vac Input 3W LED Driver Schematic . . . . . . . . . . . . . . . . . . . . . . . . . . 20

Figure 10. 12Vac Input 5W LED Driver Schematic . . . . . . . . . . . . . . . . . . . . . . . . . . 22

Figure 11. 6 to 12Vdc Input 1W LED Driver Schematic . . . . . . . . . . . . . . . . . . . . . . . 24

Figure 12. 6 to 12Vdc Input 3W LED Driver Schematic . . . . . . . . . . . . . . . . . . . . . . . 26

Figure 13. 6 to 12Vdc Input 5W LED Driver Schematic . . . . . . . . . . . . . . . . . . . . . . . 28

Figure 14. 6 to 24Vdc Input 1W LED Driver Schematic . . . . . . . . . . . . . . . . . . . . . . . 30

Figure 15. 6 to 24Vdc Input 3W LED Driver Schematic . . . . . . . . . . . . . . . . . . . . . . . 32

Figure 16. 6 to 24Vdc Input 5W LED Driver Schematic . . . . . . . . . . . . . . . . . . . . . . . 34

4/38

AN2259

Tables

Table 1.

Bill of Matarials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

Table 2.

Components Changes For Different Configuration . . . . . . . . . . . . . . . . . . 16

Table 3.

12Vac Input 1W LED Driver Bill of Materials . . . . . . . . . . . . . . . . . . . . . . . 19

Table 4.

12Vac Input 3W LED Driver Bill of Materials . . . . . . . . . . . . . . . . . . . . . . . 21

Table 5.

12Vac Input 5W LED Driver Bill of Materials . . . . . . . . . . . . . . . . . . . . . . . 23

Table 6.

6 to 12Vdc Input 1W LED Driver Bill of Materials . . . . . . . . . . . . . . . . . . . 25

Table 7.

6 to 12Vdc Input 3W LED Driver Bill of Materials . . . . . . . . . . . . . . . . . . . 27

Table 8.

6 to 12Vdc Input 5W LED Driver Bill of Materials . . . . . . . . . . . . . . . . . . . 29

Table 9.

6 to 24Vdc Input 1W LED Driver Bill of Materials . . . . . . . . . . . . . . . . . . . 31

Table 10. 6 to 24Vdc Input 3W LED Driver Bill of Materials . . . . . . . . . . . . . . . . . . . 33

Table 11. 6 to 24Vdc Input 5W LED Driver Bill of Materials . . . . . . . . . . . . . . . . . . . 35

5/38

1 DESCRIPTION OF BOARD

1 DESCRIPTION BOARD

AN2259

The evaluation board shown in

Figure 1.

was designed so that it can be configured to accept

several different input voltages that are common for automotive and lighting applications. The most common input voltages are 12Vac, 12Vdc (for automotive) and 24Vdc. The board also allows the user to select the output current using the jumpers J2 and J4 on the board without having to change any components on the evaluation board. The standard configuration of the board includes a full wave bridge rectifier that is required for an AC input

6/38

AN2259

2 INPUT CAPACITOR SELECTION

2 INPUT CAPACITOR SELECTION

For DC input, the input capacitor, C1, is selected based on its ripple current rating for the capacitor. The ripple current is calculated based on its duty cycle as outlined below.

D

=

Vo

Vin

Where D = duty cycle

Vo = output voltage

Vin = input voltage

The RMS current through the capacitor therefore is:

Iripple

=

Io D

−

2

⋅

D

η

2

+

D

2

η

2

µ

= efficiency

For an AC input voltage, the input capacitor is selected primarily to have enough capacity to supply the LED between the peaks of the AC input. The capacitor must be selected so that the minimum voltage at the input to the L5973D is maintained during each half cycle of the AC input.

Vpeak

=

2

⋅

Vin

If the application is driving only one LED, the Vmin is determined by the minimum operating voltage specification for the L5973D (4.4V). When driving more than one LED in series, the minimum input voltage is determined by the output voltage and the minimum differential input to output voltage for the regulator (the drop out voltage). In this case V min

= (x * Vf) + (I out

* R sense

)

+ V

DO

Where: x = number of LED in series

V f

= forward voltage of one LED

I o

= LED drive current

V

DO

= Drop out voltage

The capacitor can then be selected using the equation:

C

=

5

⋅

10

−

3

⋅

Io

⋅

Vo

η ⋅

(

1

2

⋅

Vpeak

2

−

1

2

⋅

V min

2

)

The ripple current rating will have two parts where in the low frequency range, the capacitor will be charged by 120Hz while at the high frequency range the capacitor is discharged by 250kHz.

For the low frequency part, it is approximately the same as the input RMS current and the power factor is approximately 0.7 for a full wave rectifier.

7/38

2 INPUT CAPACITOR SELECTION

AN2259

Iin

=

Io

Vin

⋅

⋅

Vo

η ⋅

0 .

7

For the high frequency part (ignoring output current ripple), we have:

Iripple

=

Dav

−

2

⋅

Dav

2

η

+

Dav

2

η

2

⋅

Io

where Dav is the average duty cycle.

We will use the average duty cycle assuming that the voltage on the capacitor changes from the peak to the minimum voltage linearly.

Dav

=

Vo

Vav

Vav

=

Vpeak

+

2

V min

Iripple

=

Dav

−

2

⋅

Dav

2

η

+

Dav

2

η

2

⋅

Io

The equivalent series resistance of an aluminum capacitor has different frequency characteristics. There is a coefficient associated with different frequencies. Typically, for 120Hz,

Kfl=1; for frequency greater than 10 kHz, Kfh=1.5.

Icap

=







Iin

Kfl







2

+







Iripple

Kfh







2

Therefore, the ripple current rating of the capacitor has to be greater than Icap

8/38

AN2259

3 CURRENT FEEDBACK LOOP

3 CURRENT FEEDBACK LOOP

To drive LEDs in a constant current mode, the feedback for the regulator is taken by sensing the voltage drop across the current sense resistor, Rs, as shown in

Figure 2.

The voltage divider between the sense resistor and the feedback pin (R

1

and R

2

) scales the voltage at the feedback pin so that it equals the internal reference voltage at the desired current level.

Figure 2.

Current feedback

In order to get Io = 350 mA, the values of R1, R2 and Rs are selected based on the following values.

Vref = 3.3V ; Vfb = 1.235V ; Ifb_bias = 2.5 10

-6

A ; Rs=0.68

Ω

Vsense=Rs.Io

Using the superposition method:

Vsense

Vfb

=

Vref

⋅

R 2

R 1

+

R 2

+

Vsense

⋅

R 1

R 1

+

R 2

+

Ifb _ bias

⋅

R 1

⋅

R 1

+

R 2

R 2

=

Vfb

−

( Vref

−

Vfb )

⋅

R 2

R 1

−

Ifb _ bias

⋅

R 2

Io

=

Vsense

Rs

Io

=

Vfb

−

( Vref

−

Vfb )

⋅

R 2

R 1

−

Ifb _ bias

⋅

R 2

Rs

Since Vref and Vfb come from same band gap, they are directly correlated. K=Vref/Vfb=2.672.

Therefore, the equation can be simplified to:

Io

=





1

−

( K

−

1 )

⋅

R 2

R 1





⋅

Vfb

Rs

−

Ifb _ bias

⋅

R 2

For 350mA output the selected values are:

R1 = 2.74k

Ω

,

R2 =1.30k

Ω

and

Rs = 0.68

Ω

.

9/38

3 CURRENT FEEDBACK LOOP

AN2259

For an output current of 700mA the value of Rs would be 0.34

Ω

. If R1 and R2 are small enough, the effect of the bias current can be ignored.

On the evaluation board, the value of Rs is selected by jumpers J2 and J4. When both J2 and

J4 are open, the output current is set to 350mA. Inserting each jumper connects a 0.68

resistor in parallel with the 0.68

Ω

Ω

Rs. With J2 shorted, the output current will be set to 700mA and the output current becomes 1A with both J2 and J4 shorted.

10/38

AN2259

4 INDUCTOR SELECTION

The output inductor is selected to limit the ripple current in the LEDs.

For example, for a given DC input voltage and an output current of 350mA, the peak current can be fixed to 500mA. This implies a

∆

Imax = 300mA.

For an output current of 700mA, the peak current can be fixed to1000mA. This implies a

∆

Imax= 600mA

Lmin=

Vin

−

Vo

∆

Im ax

⋅

Ton

Figure 3.

Ripple Current (One 1W LED)

Figure 3.

shows the ripple current measured with one 1W LED (warm white) at the output with

12Vac input. The measured ripple current is 180mA.

11/38

4 INDUCTOR SELECTION

Figure 4.

Ripple current (One 5W LED)

AN2259

Figure 4.

shows the ripple current driving one 5W LED at 1.05 A from a 12Vac input. The input

current is 269mA.

12/38

AN2259

5 BOARD LAYOUT

The layout for the evaluation board is shown below in

Figure 5.

and

Figure 6.

The area within

the circle in the center of the board illustrates the required area for the final application. The components outside of the circle are connectors for convenience and the auxiliary devices that allow the current to be selected on this board without changing the resistor values. Obviously the final application would use a single resistor for R

S

that is optimized for the application.

Figure 5.

Top side of Board (not in scale)

Figure 6.

Bottom side of Board (not in scale)

13/38

5 BOARD LAYOUT

Figure 7.

Board Schematic

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14/38

AN2259

5 BOARD LAYOUT

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

Table 1.

Bill of Matarials

Qty

Part

Reference

Part Description

1

1

C1

C2

Mfg P/N

1200uF/35V electrolytic EEU-FC1V22L

220pF/50V ceramic

5

1

Mfg

Panasonic

Geometry Mounting

Radial

J4

L1

Q1

Rs

Rs2

Rs3

R1

R2

R3

R4

U1

C3

C4

C5

22nF/50V ceramic

22nF/50V ceramic

4.7nF/50V ceramic

D2 D4 D5

D6 D7

J1

J2

Low Drop Power

Schottky Rectifier

Phoenix 2 Pin

Connector

STPS2L40U

MKDSN1.5/2

Current Select Jumper 22-28-8020

STMicroelectronics

Phoenix Contact

Molex

J3 Stackable Receptacle 535676-5 Tyco

SMB

Current Select Jumper 22-28-8020

Inductor DO3316P-683

PNP Transistor

Molex

Coilcraft

6 Pin

MMBT3906

STMicroelectronics

SOT23

0.68ohms 1% 1/4W

0.68ohms 1% 1/4W

0.68ohms 1% 1/4W

2.74kohms 1% 1/8W

1.30kohms 1% 1/8W

4.7kohms 5% 1/8W

240kohms 5% 1/8W

Step-down controller L5973D

STMicroelectronics

2010

2010

2010

0805

0805

0805

0805

SO8

TH

SMD

SMD

SMD

SMD

SMD

TH

SMD

SMD

SMD

SMD

SMD

SMD

SMD

SMD

TH

TH

TH

SMD

SMD

15/38

6 REFERENCE DESIGN VERSIONS

6 REFERENCE DESIGN VERSIONS

AN2259

The evaluation board is designed to display the full functionality of L5973D as a LED driver to drive one to three 1W, 3W as well as 5W LEDs at 12Vac input. The components selected for the demo board are optimized for 5W LED driver application. Based on this circuit, there are nine different configurations with different input voltages and output power levels that could be derived by making minor components changes to the evaluation board.

Table 1.

shows the component changes needed in order to obtain each configuration. The final schematics and bill of materials for each configuration are shown in the subsequent pages. The 6 to 12 Vdc input configuration was designed for automotive applications that must survive a reverse battery condition. In this case one of the rectifiers remains on the board to provide protection against reversing the power supply leads.

Table 2.

Components Changes For Different Configuration

LED Driver U1 D4 D5

12Vac

1W LED

12Vac

3W LED

12Vac

5W LED

6-12Vdc

1W LED

6-12Vdc

3W LED

6-12Vdc

5W LED

6-24Vdc

1W LED

6-24Vdc

3W LED

6-24Vdc

5W LED

L5970D

L5973D

L5973D

L5970D

L5973D

L5973D

L5970D

L5973D

L5973D

STPS1L40A

STPS2L40U

STPS2L40U

Not used

Not used

Not used

Not used

Not used

Not used

STPS1L40A

STPS2L40U

STPS2L40U

Not used

Not used

Not used

Not used

Not used

Not used

D6

STPS1L40A

STPS2L40U

STPS2L40U

STPS1L40A

STPS2L40U

STPS2L40U

Jumper wire

Jumper wire

Jumper wire

D7

STPS1L40A

STPS2L40U

STPS2L40U

Jumper wire

Jumper wire

Jumper wire

Jumper wire

Jumper wire

Jumper wire

16/38

AN2259

Table 2. (Continued)

C1

680uF/35V

1200uF/35V

1200uF/35V

27uF/50V

68uF/50V

100uF/50V

22uF/35V

68uF/35V

100uF/35V

R2

1.30k 1%

1.33k 1%

1.30k 1%

1.30k 1%

1.33k 1%

1.30k 1%

1.30k 1%

1.33k 1%

1.30k 1%

0.33

0.24

0.68

0.33

0.24

Rs

0.68

0.33

0.24

0.68

6 REFERENCE DESIGN VERSIONS

L1

47uH

33uH

68uH

47uH

33uH

68uH

100uH

100uH

100uH

D2

STPS1L40A

STPS2L40U

STPS2L40U

STPS1L40A

STPS2L40U

STPS2L40U

STPS1L40A

STPS2L40U

STPS2L40U

17/38

6 REFERENCE DESIGN VERSIONS

Figure 8.

12Vac Input 1W LED Driver Schematic

1 2

2 1

2 1

GND

7

INH

3

2 1

1 3

2 1 2 1

2

1

1

1

2 1

18/38

AN2259

AN2259

6 REFERENCE DESIGN VERSIONS

1

2

1

5

1

1

1

1

1

1

1

Table 3.

12Vac Input 1W LED Driver Bill of Materials

Qty Reference

Part

Description

Mfg P/N Mfg

1 C1

680uF/35V

Electrolytic

EEU-FC1V681 Panasonic

1

C2

C3, C4

C5

D2, D4, D5,

D6, D7

L1

Q1

Rs

R1

R2

R3

R4

U1

Geometry

Radial

Mtg

TH

220pF/50V

Ceramic

22nF/50V

Ceramic

4.7nF/50V

Ceramic

SMD

SMD

SMD

Schottky Diode

1A/40V

STPS1L40A

47uH Inductor DO3308P-473

STMicroelectronics

Coilcraft

SMA SMD

9.4mmx12.95mm SMD

PNP Transistor

0.68 Ohm 1%

2.74k 1%

1.30k 1%

4.7k 5%

240k 5%

Step-down controller

MMBT3906

L5970D

STMicroelectronics

STMicroelectronics

SOT-23

1206

0805

0805

0805

0805

0SO8

SMD

SMD

SMD

SMD

SMD

SMD

SMD

19/38

6 REFERENCE DESIGN VERSIONS

Figure 9.

12Vac Input 3W LED Driver Schematic

20/38

1 2

2 1

2 1

GND

7

INH

3

2 1

1 3

2 1 2 1

2

1

1

1

2 1

AN2259

AN2259

6 REFERENCE DESIGN VERSIONS

Table 4.

12Vac Input 3W LED Driver Bill of Materials

Qty Reference

Part

Description

Mfg P/N Mfg

1

1

2

1

5

1

1

1

1

1

1

1

1

C1

C2

C3, C4

C5

D2, D4, D5,

D6, D7

L1

Q1

Rs

R1

R2

R3

R4

U1

Geometry Mtg

1200uF/35V

Electrolytic

220pF/50V

Ceramic

22nF/50V

Ceramic

EEU-

FC1V122L

Panasonic Radial TH

SMD

SMD

4.7nF/50V

Ceramic

Schottky Diode

2A/40V

33uH Inductor DO3308P-333 Coilcraft

PNP Transistor MMBT3906

STMicroelectronics

9.4mmx12.95mm SMD

SOT-23 SMD

0.33 Ohm 1%

STPS2L40U

CRL2010-FW-

R330E

STMicroelectronics

Bourns

SMB

2010

SMD

SMD

SMD

2.74k 1%

1.33k 1%

4.7k 5%

240k 5%

Step-down controller

L5973D

STMicroelectronics

0805

0805

0805

0805

SO8

SMD

SMD

SMD

SMD

SMD

21/38

6 REFERENCE DESIGN VERSIONS

Figure 10. 12Vac Input 5W LED Driver Schematic

2 1

2 1

INH

GND

3

7

C3 22

R3 4.

2 1

1 3

C5 4.

C1 120

C2 22

1

D4 ST

1

22/38

AN2259

AN2259

6 REFERENCE DESIGN VERSIONS

Table 5.

12Vac Input 5W LED Driver Bill of Materials

Qty Reference

Part

Description

Mfg P/N Mfg

1

1

2

1

5

1

1

1

1

1

1

1

1

C1

C2

C3, C4

C5

D2, D4, D5,

D6, D7

L1

Q1

Rs

R1

R2

R3

R4

U1

Geometry Mtg

1200uF/35V

Electrolytic

220pF/50V

Ceramic

22nF/50V

Ceramic

EEU-

FC1V122L

Panasonic Radial TH

SMD

SMD

4.7nF/50V

Ceramic

Schottky Diode

2A/40V

68uH Inductor DO3316P-683 Coilcraft

PNP Transistor MMBT3906

STMicroelectronics

9.4mmx12.95mm SMD

SOT-23 SMD

0.24 Ohm 1%

STPS2L40U

CRL2010-FW-

R240E

STMicroelectronics

Bourns

SMB

2010

SMD

SMD

SMD

2.74k 1%

1.30k 1%

4.7k 5%

240k 5%

Step-down controller

L5973D

STMicroelectronics

0805

0805

0805

0805

SO8

SMD

SMD

SMD

SMD

SMD

23/38

6 REFERENCE DESIGN VERSIONS

Figure 11. 6 to 12Vdc Input 1W LED Driver Schematic

1 2

2 1

2 1

GND

7

INH

3

2 1

1 3

AN2259

24/38

AN2259

6 REFERENCE DESIGN VERSIONS

Table 6.

6 to 12Vdc Input 1W LED Driver Bill of Materials

Qty Reference

Part

Description

Mfg P/N Mfg

1

1

2

1

2

1

1

1

1

1

1

1

1

1

C1

C2

C3, C4

C5

D2, D6

D7

L1

Q1

Rs

R1

R2

R3

R4

U1

Geometry Mtg

27uF/50V

Electrolytic

220pF/50V

Ceramic

22nF/50V

Ceramic

4.7nF/50V

Ceramic

Schottky Diode

1A/40V

EEU-

FC1H270

STPS1L40A

Panasonic

STMicroelectronics

Radial

SMA

TH

SMD

SMD

SMD

SMD

Jumper at D7 position

47uH Inductor DO3308P-473 Coilcraft

PNP Transistor MMBT3906

STMicroelectronics

0.68 Ohm 1%

2.74k 1%

1.30k 5%

4.7k 5%

240k 5%

Step-down controller

L5970D

STMicroelectronics

SMD

9.4mmx12.95mm SMD

SOT-23

1206

0805

0805

0805

0805

SO8

SMD

SMD

SMD

SMD

SMD

SMD

SMD

25/38

6 REFERENCE DESIGN VERSIONS

Figure 12. 6 to 12Vdc Input 3W LED Driver Schematic

1 2

2 1

2 1

GND

7

INH

3

2 1

1 3

AN2259

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AN2259

6 REFERENCE DESIGN VERSIONS

Table 7.

6 to 12Vdc Input 3W LED Driver Bill of Materials

Qty Reference

Part

Description

Mfg P/N Mfg

1

1

2

1

2

1

1

1

1

1

1

1

1

1

C1

C2

C3, C4

C5

D2, D6

D7

L1

Q1

Rs

R1

R2

R3

R4

U1

Geometry Mtg

68uF/50V

Electrolytic

220pF/50V

Ceramic

22nF/50V

Ceramic

4.7nF/50V

Ceramic

Schottky Diode

2A/40V

Jumper at D7 position

EEU-

FC1H680

STPS2L40U

Panasonic

STMicroelectronics

Radial D8mm

805

805

805

SMB

TH

SMD

SMD

SMD

SMD

SMD

33uH Inductor DO3308P-333 Coilcraft

PNP Transistor MMBT3906

STMicroelectronics

0.33 Ohm 1%

CRL2010-FW-

R330E

Bourns

9.4mmx12.95mm SMD

SOT-23 SMD

2010 SMD

2.74k 1%

1.33k 1%

4.7k 5%

240k 5%

Step-down controller

L5973D

STMicroelectronics

0805

0805

0805

0805

SO8

SMD

SMD

SMD

SMD

SMD

27/38

6 REFERENCE DESIGN VERSIONS

Figure 13. 6 to 12Vdc Input 5W LED Driver Schematic

2 1

2 1

C1 1

INH

GND

3

7

C3 22 R3 4.

2 1

1 3

C5 4.

C2 2

AN2259

28/38

AN2259

6 REFERENCE DESIGN VERSIONS

Table 8.

6 to 12Vdc Input 5W LED Driver Bill of Materials

Qty Reference

Part

Description

Mfg P/N Mfg

1

1

2

1

2

1

1

1

1

1

1

1

1

1

C1

C2

C3, C4

C5

D2, D6

D7

L1

Q1

Rs

R1

R2

R3

R4

U1

Geometry Mtg

100uF/50V

Electrolytic

220pF/50V

Ceramic

22nF/50V

Ceramic

4.7nF/50V

Ceramic

Schottky Diode

2A/40V

Jumper at D7 position

EEU-

FC1H101

STPS2L40U

Panasonic

STMicroelectronics

Radial D8mm

805

805

805

SMB

TH

SMD

SMD

SMD

SMD

SMD

68uH Inductor DO3316P-683 Coilcraft

PNP Transistor MMBT3906

STMicroelectronics

0.24 Ohm 1%

CRL2010-FW-

R240E

Bourns

9.4mmx12.95mm SMD

SOT-23 SMD

2010 SMD

2.74k 1%

1.30k 1%

4.7k 5%

240k 5%

Step-down controller

L5973D

STMicroelectronics

0805

0805

0805

0805

SO8

SMD

SMD

SMD

SMD

SMD

29/38

6 REFERENCE DESIGN VERSIONS

Figure 14. 6 to 24Vdc Input 1W LED Driver Schematic

1 2

2 1

2 1

GND

7

INH

3

2 1

1 3

AN2259

30/38

AN2259

6 REFERENCE DESIGN VERSIONS

1

1

1

1

1

1

1

Table 9.

6 to 24Vdc Input 1W LED Driver Bill of Materials

Qty Reference

Part

Description

Mfg P/N Mfg

1 C1

EEU-

FC1H220

Panasonic

1

2

1

1

1

1

C2

C3, C4

C5

D2

D7

D6

22uF/35V

Electrolytic

220pF/50V

Ceramic

22nF/50V

Ceramic

4.7nF/50V

Ceramic

Schottky Diode

1A/40V

Jumper at D7 position

Jumper at D6 position

STPS1L40A

STMicroelectronics

1 L1 100uH Inductor DO3308P-104 Coilcraft

Q1

Rs

R1

R2

R3

R4

U1

PNP Transistor MMBT3906

STMicroelectronics

0.68 Ohm 1%

2.74k 1%

1.30k 1%

4.7k 5%

240k 5%

Step-down controller

L5970D

STMicroelectronics

Geometry Mtg

9.4mm x

12.95mm

SOT-23

1206

0805

0805

0805

0805

SO8

Radial TH

SMD

SMD

SMD

SMA SMD

SMD

SMD

SMD

SMD

SMD

SMD

SMD

SMD

SMD

SMD

31/38

6 REFERENCE DESIGN VERSIONS

Figure 15. 6 to 24Vdc Input 3W LED Driver Schematic

1 2

2 1

2 1

GND

7

INH

3

2 1

1 3

AN2259

32/38

AN2259

6 REFERENCE DESIGN VERSIONS

1

1

1

1

1

1

1

Table 10.

6 to 24Vdc Input 3W LED Driver Bill of Materials

Qty Reference

Part

Description

Mfg P/N Mfg

1 C1

EEU-

FC1V680

Panasonic

1

2

1

1

1

1

C2

C3, C4

C5

D2

D6

D7

68uF/35V

Electrolytic

220pF/50V

Ceramic

22nF/50V

Ceramic

4.7nF/50V

Ceramic

Schottky Diode

2A/40V

Jumper at D6 position

Jumper at D7 position

STPS2L40U

STMicroelectronics

1 L1 100uH Inductor DO3316P-104 Coilcraft

Q1

Rs

R1

R2

R3

R4

U1

PNP Transistor MMBT3906

STMicroelectronics

0.33 Ohm 1%

CRL2010-FW-

R330E

Bourns

2.74k 1%

1.33k 1%

4.7k 5%

240k 5%

Step-down controller

L5973D

STMicroelectronics

Geometry Mtg

9.4mm x

12.95mm

SOT-23

2010

0805

0805

0805

0805

SO8

Radial TH

SMD

SMD

SMD

SMB SMD

SMD

SMD

SMD

SMD

SMD

SMD

SMD

SMD

SMD

SMD

33/38

6 REFERENCE DESIGN VERSIONS

Figure 16. 6 to 24Vdc Input 5W LED Driver Schematic

2 1

2 1

C1 10

INH

GND

3

7

C3 22n

R3 4.

2 1

1 3

C2 22

AN2259

34/38

AN2259

6 REFERENCE DESIGN VERSIONS

1

1

1

1

1

1

1

Table 11.

6 to 24Vdc Input 5W LED Driver Bill of Materials

Qty Reference

Part

Description

Mfg P/N Mfg

1 C1

EEU-

FC1V101

Panasonic

1

2

1

1

1

1

C2

C3, C4

C5

D2

D6

D7

100uF/35V

Electrolytic

220pF/50V

Ceramic

22nF/50V

Ceramic

4.7nF/50V

Ceramic

Schottky Diode

2A/40V

Jumper at D6 position

Jumper at D7 position

STPS2L40U

STMicroelectronics

1 L1 100uH Inductor DO3316P-104 Coilcraft

Q1

Rs

R1

R2

R3

R4

U1

PNP Transistor MMBT3906

STMicroelectronics

0.24 Ohm 1%

CRL2010-FW-

R240E

Bourns

2.74k 1%

1.30k 1%

4.7k 5%

240k 5%

Step-down controller

L5973D

STMicroelectronics

Geometry Mtg

9.4mm x

12.95mm

SOT-23

2010

0805

0805

0805

0805

SO8

Radial TH

SMD

SMD

SMD

SMB SMD

SMD

SMD

SMD

SMD

SMD

SMD

SMD

SMD

SMD

SMD

35/38

7 REVISION HISTORY

Date

04-Nov-2005

Revision

1.0

First edition

Changes

AN2259

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7 REVISION HISTORY

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7 REVISION HISTORY

AN2259

Information furnished is believed to be accurate and reliable. However, STMicroelectronics assumes no responsibility for the consequences of use of such information nor for any infringement of patents or other rights of third parties which may result from its use. No license is granted by implication or otherwise under any patent or patent rights of STMicroelectronics. Specifications mentioned in this publication are subject to change without notice. This publication supersedes and replaces all information previously supplied. STMicroelectronics products are not authorized for use as critical components in life support devices or systems without express written approval of STMicroelectronics.

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