LT3486 Datasheet, PDF (1/20 Pages) Linear Technology – Dual 1.3A White LED Step-Up Converters with Wide Dimming

LT3486
Dual 1.3A White LED
Step-Up Converters with
Wide Dimming
FEATURES
■ _{Wide (1000:1) PWM Dimming Range with No}
ColorShift
■ _{Independent Dimming and Shutdown Control of the}
LED Drivers
■ _{Drives Up to 16 White LEDs at 25mA (8 per Driver)}
from a Single Li-Ion Cell
■ _{Drives Up to 16 White LEDs at 100mA (8 per Driver)}
from 12V Supply
■ _{±3% LED Current Programming Accuracy}
■ _{Open LED Protection: 36V Clamp Voltage}
■ _{Fixed Frequency Operation: Up to 2MHz}
■ _{Wide Input Voltage Range: 2.5V to 24V}
■ _{Low Shutdown Current: ICC < 1µA}
■ _{Overtemperature Protection}
■ _{Available in (5mm × 3mm × 0.75mm) 16-Pin DFN}
and 16-Pin Thermally Enhanced TSSOP Packages
U
APPLICATIO S
■ _{Notebook PC Display}
■ _{LED Camera Light for Cell Phones}
■ _{Car Dashboard Lighting}
■ _{Avionics Displays}
DESCRIPTIO
The LT^®3486 is a dual step-up DC/DC converter
specifically designed to drive up to 16 White LEDs (8 in
series per converter) at constant current from a single
Li-Ion cell. Series connection of the LEDs provides identi-
cal LED currents resulting in uniform brightness. The two
independent converters are capable of driving asymmetric
LED strings.
The dimming of the two LED strings can be controlled
independently via the respective CTRL pins. An internal
dimming system allows the dimming range to be extended
up to 1000:1 by feeding a PWM signal to the respective
PWM pins. The LT3486 operating frequency can be set with
an external resistor over a 200kHz to 2MHz range. A low
200mV feedback voltage (±3% accuracy) minimizes power
loss in the current setting resistor for better efficiency.
Additional features include output voltage limiting when
LEDs are disconnected and overtemperature protection.
The LT3486 is available in a space saving 16-pin DFN
(5mm × 3mm × 0.75mm) and 16-pin thermally enhanced
TSSOP packages.
, LTC and LT are registered trademarks of Linear Technology Corporation.
All other trademarks are the property of their respective owners. Patent Pending.
TYPICAL APPLICATIO
Li-Ion Powered Driver for Camera Flash and LCD Backlighting
V_IN
3V TO 4.2V
2.2µF
LED1
AOT3218
DIMMING 1
OFF ON
OFF ON
100k
10µF
L1
10µH
L2
10µH
SW1
V_IN
SW2
OVP1
OVP2
2.2µF
CTRL1
CTRL2 DIMMING 2
SHDN
PWM1
LT3486
REF
PWM2
0.1µF
FB1
FB2
V_C1
R_T
V_C2
R_FB1
0.62Ω
0.1µF
63.4k
2.8k
4.7nF
8 LEDs
25mA
R_FB2
8.06Ω
3486 TA01a
Efficiency vs V_IN
90
MOVIE MODE
I_LED1 = 175mA
85
FLASH MODE
80
I_LED1 = 320mA
75
70
8 LEDS/25mA
65
3 3.2 3.4 3.6 3.8
V_IN (V)
4 4.2
3486 TA01b
3486f
1