LDS8720

© 2011 IXYS Corp.

1

Doc. No. 8720DS, Rev. N1.1

Characteristics subject to change without notice

184 WLED Matrix Driver with Boost Converter

FEATURES

 High efficiency boost converter with the input

voltage range from 2.7 to 5.5 V

 No external Schottky Required (Internal

synchronous rectifier)

 250 mV current sense voltage

 Drives up to 10 LEDs per string

 More than 180 LEDs in matrix

 0.7 MHz Switching Frequency

 Efficiency greater than 83%

 PWM LED Dimming Control Mode

 Over-voltage, under-voltage, over-current,

and over-temperature protection

 Low Shutdown Current (<1µA)

 Available in 2 x 3 x 0.8 mm 8-pin TDFN

package

APPLICATION

 Color Display Backlight

 Portable Navigation and GPS Receivers

 Smart phones

 Digital Photo Frames

 Portable DVD Players

 Architectural Lighting

DESCRIPTION

The LDS8720 is a fixed frequency current mode

boost converter with internal synchronous rectifier

and cycle-by-cycle switch current limit specifically

designed to drive matrix of LEDs in respect with the

Table 1. Operation at 0.7 MHz allows use of small

value low profile inductor (10 – 33 µH) and 1 µF 50 V

ceramic capacitor.

TYPICAL APPLICATION CIRCUIT

The use of integrated synchronous rectifier makes

the

efficiency dependent

on

only inductor DC

resistance. Under-voltage protection disables the part

up to 15 V to increase power capability of the driver.

Maximum number of LEDs in matrix depends on this

voltage as shown in the table below.

The LDS8720 has thermal shutdown set at 150

Above

this

value ,

the

boost

converter

stops

switching. The part resumes normal operations when

temperature drops below 130

The over-current protection provides cycle-by-cycle

current limit.

The internal output over-voltage protection prevents

damage in the case of a faulty LED disconnect.

The PWM control ensures brightness adjustment with

a frequency from 100 Hz up to 30 KHz.

The EN/PWM logic input functions as a chip enable

and LED current PWM contol pin.

The device is available in 8-pin TDFN 2 x 3 mm

package with a max height of 0.8 mm.

Table 1 Matrix configuration for LDS8720

Number of

LED per string

String

Current

max, mA,

Number

of strings

2.7

10

30

1 – 3

3.0

10

30

1 – 4

4.0

10

30

1 – 5

5.0

10

30

1 – 6

7.5

10

30

1 – 9

10

10

30

1 – 12

12.5

10

30

1 – 15

15

10

30

1 – 18

15

8

30

1 – 23