Jun26-07 Rev D

Micro Power Boost Regulator Series White LED Driver

© 2007 Sipex Corporation

/TR = Tape and Reel

Pack quantity is 2,500 for TSOT or SOT-23 and 3,000 for DFN.

Available in lead free packaging. To order add "-L" suffix to part number.

Example: SP6691ER/TR = standard; SP6691ER-L/TR = lead free

ORDERING INFORMATION

Part Number

Temperature Range

Package Type

SP6691EK1 .......................................................... -40˚C to +85˚C ............................. 5 Pin TSOT

SP6691EK1/TR ..................................................... -40˚C to +85˚C ............................ 5 Pin TSOT

SP6691EK ............................................................ -40˚C to +85˚C .......................... 5 Pin SOT-23

SP6691EK/TR ....................................................... -40˚C to +85˚C ......................... 5 Pin SOT-23

SP6691ER ............................................................ -40˚C to +85˚C ............................... 8 Pin DFN

SP6691ER/TR ...................................................... -40˚C to +85˚C .............................. 8 Pin DFN

Output Voltage Program

The SP6691 can be programmed as either a

voltage source or a current source. To program

the SP6691 as voltage source, the SP6691 re-

the output voltage. As shown in Figure 22.

Table 4. Divider Resistor Selection

Brightness Control

Dimming control can be achieved by applying a

PWM control signal to the SHDN pin. The

brightness of the white LEDs is controlled by

increasing and decreasing the duty cycle of the

PWM signal. A 0% duty cycle corresponds to

zero LED current and a 100% duty cycle corre-

sponds to full load current. While the operating

frequency range of the PWM control is from

60Hz to 700Hz, the recommended maximum

brightness frequency range of the PWM signal

is from 60Hz to 200Hz. A repetition rate of at

least 60Hz is required to prevent flicker. The

magnitude of the PWM signal should be higher

than the minimum SHDN voltage high.

Open Circuit Protection

When any white LED inside the white LED

module fails or the LED module is disconnected

from the circuit, the output and the feedback

control will be open, thus resulting in a high

output voltage, which may cause the SW pin

voltage to exceed it maximum rating. In this

case, a zener diode can be used at the output to

limit the voltage on the SW pin and protect the

part. The zener voltage should be larger than the

maximum forward voltage of the White LED

module.

APPLICATION INFORMATION: Continued

L1

1.22V

R2

D1

C1

C2

R1

VOUT

U1

SP6691

1

2

3

4

5

S W

G ND

FB

SHDN

V

I N

VIN

Figure 22. Using SP6691 as Voltage Source

The formula and table for the resistor selection

are shown below:

1.22

precision resistors are recommended. Table 3

LED currents. For example, to set the operating

, as

shown in the schematic.

Table 3. Bias Resistor Selection

)

5

243

10

121

12

102

15

80.6

20

60.4

)

)

12

1M

113K

15

1M

88.7K

18

1M

73.2K

21

1M

61.9K

30

1M

42.2K

Sipex corporation

Headquarters and

Sales Office

2 South Hillview Drive

Milpitas, CA 0

TEL: (0) -700

FAX: (0) -7600

Sipex Corporation reserves the right to make changes to any products described herein. Sipex does not assume

any liability arising out of the application or use of any product or circuit described herein; neither does it convey

any license under its patent rights nor the rights of others.

Solved by

TM

For further assistance:

Email:

Sipexsupport@sipex.com

WWW Support page:

http://www.sipex.com/content.aspx?p=support

Sipex Application Notes:

http://www.sipex.com/applicationNotes.aspx