FEATURES
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LT3498
20mA LED Driver and
OLED Driver with Integrated
Schottky in 3mm x 2mm DFN
DESCRIPTION
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
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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
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Cellular Phones
PDAs, Handheld Computers
Digital Cameras
MP3 Players
GPS Receivers
TYPICAL APPLICATION
Li-Ion to Six White LEDs and OLED/LCD Bias
80
V
IN
= 3V TO 5V
4.7µF
0.47µF
OLED Efficiency
75
70
EFFICIENCY (%)
16V
24mA
V
IN
= 3.6V
V
OUT2
= 16V
LOAD FROM V
OUT2
400
350
300
POWER LOSS (mW)
250
200
150
100
15µH
1µF
10Ω
CAP1 SW1
V
IN
15µH
SW2 CAP2 V
OUT2
65
60
55
50
45
40
0.1
POWER LOSS
FROM V
OUT2
1
10
LED CURRENT (mA)
10µF
LT3498
LED1
20mA
CTRL1
OFF ON
SHUTDOWN
AND
DIMMING
CONTROL
3498 TA01
GND1
GND2
CTRL2
OFF ON
SHUTDOWN
AND
CONTROL
FB2
2.21MΩ
50
0
100
3498 TA01b
3498f
1
LINER [ LINEAR TECHNOLOGY ]
