LDS8724 Datasheet, PDF (1/10 Pages) IXYS Corporation – 40 WLED Driver with Boost Converter

LDS8724
40 WLED 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 5 LEDs per string with up to 42
LED in 6 strings at 25 mA
 1 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, Notebooks
DESCRIPTION
The LDS8724 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 1 MHz allows use of small
value low profile inductor (10 – 33 µH) and 1 µF 50 V
ceramic capacitor.
The use of integrated synchronous rectifier makes
the efficiency dependent on only inductor DC
TYPICAL APPLICATION CIRCUIT
resistance. Under-voltage protection disables the part
when V_IN voltage reaches 2.0 V
The LDS8724 has thermal shutdown set at 150 ⁰C.
Above this value , the boost converter stops
switching. The part resumes normal operations when
temperature drops below 130 ⁰C.
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 LDS8724
Number of
strings
1-6
7, 8
9
10
11
12
Number of
LED per string
5
5
5
4
4
3
String
Current
max, mA,
30
25
25
25
25
30
V_{IN MIN}, V
2.7
2.7
3.0
2.7
3.0
3.0
*) Patent pending
© 2010 IXYS Corp.
1
Characteristics subject to change without notice
Doc. No. 8724DS, Rev. N1.0