LT3498 Datasheet, PDF (1/24 Pages) Linear Technology – 20mA LED Driver and OLED Driver with Integrated Schottky in 3mm x 2mm DFN

LT3498
FEATURES
20mA LED Driver and
OLED Driver with Integrated
Schottky in 3mm x 2mm DFN
DESCRIPTION
■ _{Dual Output Boost for Dual Display Devices}
■ _{Drives Up to Six White LEDs and OLED/LCD Bias}
■ _{Internal Power Switches and Schottky Diodes}
■ _{Independent Dimming and Shutdown}
■ _{200mV High Side Sense on LED Driver Allows}
“One-Wire Current Source”
■ _{Wide Input Voltage Range: 2.5V to 12V}
■ _{Wide Output Voltage Range: Up to 32V}
■ _{2.3MHz PWM Frequency for LED Driver}
■ _{PFM for OLED Driver is Non-Audible Over Entire}
Load Range
■ _{Open LED Protection (27V Maximum on CAP1 Pin)}
■ _{OLED Output Disconnect}
■ _{Available in 12-Pin DFN Package}
■ _{1mm Tall Solution Height}
APPLICATIONS
■ _{Cellular Phones}
■ _{PDAs, Handheld Computers}
■ _{Digital Cameras}
■ _{MP3 Players}
■ _{GPS Receivers}
The LT^®3498 is a dual output boost converter featuring a
2.3MHz PWM LED Driver and PFM OLED Driver. It includes
an internal power switch and Schottky diode for each
driver. Both converters can be independently shut down
and modulated. This highly integrated power solution is
ideal for dual display electronic devices.
The 2.3MHz step-up converter is designed to drive up to six
white LEDs in series from a Li-Ion cell. The device features
a unique high side LED current sense that enables the part
to function as a “one-wire” current source—one side of the
LED string can be returned to ground anywhere. Traditional
LED drivers use a grounded resistor to sense LED current,
requiring a 2-wire connection to the LED string.
The PFM OLED driver is a low noise boost converter that
features a novel control technique.* The converter controls
power delivery by varying both the peak inductor current
and switch off time. This technique results in low output
voltage ripple, as well as, high efficiency over a wide load
range. The off time of the switch is not allowed to exceed a
fixed level, guaranteeing a switching frequency that stays
above the audio band.
, LT, LTC and LTM are registered trademarks of Linear Technology Corporation.
All other trademarks are the property of their respective owners.
*Patent Pending
TYPICAL APPLICATION
Li-Ion to Six White LEDs and OLED/LCD Bias
V_IN = 3V TO 5V
4.7µF
0.47µF
15µH
15µH
1µF
CAP1 SW1
10Ω
V_IN
SW2 CAP2 V_OUT2
LT3498
16V
24mA
10µF
LED1 CTRL1 GND1 GND2 CTRL2 FB2
20mA
OFF _ON
SHUTDOWN
AND
DIMMING
CONTROL
OFF _ON
SHUTDOWN
AND
CONTROL
3498 TA01
2.21MΩ
OLED Efficiency
80
400
V_IN = 3.6V
75 ^{VOUT2 = 16V}
350
70
LOAD FROM V_OUT2
300
65
250
60
200
55
150
50
45
40
0.1
POWER LOSS
FROM V_OUT2
1
10
LED CURRENT (mA)
100
50
0
100
3498 TA01b
3498f
1