LTC3452 Linear Technology, LTC3452 Datasheet - Page 13

• Manufacturer Part Number: LTC3452
• Description: Synchronous Buck-Boost MAIN/CAMERA White LED Driver
• Manufacturer: Linear Technology

APPLICATIO S I FOR ATIO
Although the LTC3452 can safely provide this current
continuously, the external LED(s) may not be rated for this
high a level of continuous current. Higher current levels in
a single LED are generally reserved for pulsed applica-
tions, such as LED camera flash. This is accomplished by
programming a high current with one or both of the R
resistors and pulsing the appropriate enable pin or pins as
shown in the back page application.
VOLTAGE
DAC
V
V
IN
IN
V
R
R
R
DAC
SET
MINL
POT
U
EN
I
EN
I
SETL
SETL
≥ R
L
L
LTC3452
MINL
LTC3452
U
LED
LED
LED
LED
Figure 3. Additional Brightness Control Methods: (3a) Using Voltage DAC,
(3b) Using Current DAC, (3c) Using Potentiometer, (3d) Using PWM Input
(3a)
(3c)
L1
L5
L1
L5
I
I
LED
LED
W
= 256
= 256
V
V
OUT
OUT
0.8V – V
R
MINL
R
0.8V
SET
+ R
DAC
POT
U
ISET
CURRENT
DAC
Varying LED Brightness Linearly
Continuously variable LED brightness control can be
achieved by interfacing directly to one or both of the I
pins. Figure 3 shows four such methods employing a
voltage DAC, a current DAC, a simple potentiometer or a
PWM input applied to the I
power bank LED currents. These four techniques can be
similarly applied to the I
power bank LED currents.
R
100
SET
V
V
IN
IN
R
V
PWM
SET
1µF
IDAC ≤
EN
I
EN
I
SETL
SETL
≥ R
L
L
LTC3452
LTC3452
MINL
R
0.8V
MINL
f
PWM
LED
LED
LED
LED
(3b)
≥ 10kHz
(3d)
L1
L5
L1
L5
I
I
LED
LED
SETH
DV
= 256 • IDAC
= 256
= 256
SETL
CC
V
V
OUT
OUT
pin for controlling the high
0.8V – V
0.8V – (DC% • V
pin for controlling the low
R
www.DataSheet4U.com
SET
3452 F03
PWM
R
SET
DVCC
LTC3452
)
13
3452f
SET