LTC3230_15 Datasheet, PDF (1/16 Pages) Linear Technology – 5-LED Main/Sub Display Driver with Dual LDO

FEATURES
■ _{Low Noise Charge Pump Provides High Efficiency}
with Automatic Mode Switching
■ _{Multimode Operation: 1x, 1.5x, 2x}
■ _{Full-Scale Current Set Resistor}
■ _{Up to 125mA Total LED Current}
■ _{Single Wire Enable/Brightness Control for Main and}
Sub Display LEDs
■ _{32:1 Linear LED Brightness Control}
■ _{Dual 200mA Linear Regulators}
■ _{Four 25mA Low Dropout Main LED Current Sources}
■ _{One 25mA Low Dropout Sub LED Current Source}
■ _{Low Noise Constant Frequency Operation}
■ _{Low Shutdown Current: 3μA}
■ _{Internal Soft-Start Limits Inrush Current During}
Start-Up and Mode Switching
■ _{Open/Short LED Protection}
■ _{No Inductors}
■ _{20-Lead 3mm × 3mm QFN Package}
APPLICATIONS
■ _{Multi-LED Driver and Dual LDO Supplies for Cell}
Phone, PDA, Digital Camera and PND Applications
, LT, LTC and LTM are registered trademarks of Linear Technology Corporation.
All other trademarks are the property of their respective owners. Protected by U.S. Patents
including 6411531.
LTC3230
5-LED Main/Sub Display
Driver with Dual LDO
DESCRIPTION
The LTC^®3230 is a low noise charge pump DC/DC converter
designed to drive 4 Main LEDs and 1 Sub LED, plus two
200mA linear regulators to provide additional system
power. The LTC3230 charge pump requires only four small
ceramic capacitors and one current set resistor to form a
complete LED power supply and current controller.
Built-in soft-start circuitry prevents excessive inrush cur-
rent during start-up and mode changes. High switching
frequency enables the use of small external capacitors.
Main and Sub full-scale current settings are programmed
by a single external resistor.
Charge pump efficiency is optimized based on the voltage
across the LED current sources. The part powers up in 1x
mode and automatically switches to the next higher mode,
1.5x and subsequently 2x, whenever any LED current
source approaches dropout.
Two 200mA linear regulators have independent enable
and output voltage select pins. Each regulator can be set
to one of three pre-selected output voltages with tri-level
input pins. The regulators may be enabled independently
of the charge pump.
The LTC3230 is available in a low profile (0.75mm) 3mm
× 3mm 20-lead QFN package.
TYPICAL APPLICATION
C1
C2
1mF
1mF
V_IN = 2.7V
TO 5.5V
C1P C1M C2P C2M ^125mA
C3
V_IN
CPO
C6
MAIN
2.2mF
LTC3230
1mF D1
D2
D3
D4
ENM
ENS
R_SET
17.4k
1%
ENM
MLED1
ENS
MLED2
MLED3
MLED4
ENLDO1
SLED
ENLDO2
LDO1
V1
V2
R_{SET GND} LDO2
1.5V
C4
1mF
200mA
2.8V
C5
1mF
200mA
ENM OR ENS
SET BRIGHTNESS LEVEL ON OFF
SUB
D5
3230 TA01a
Efficiency vs V_IN Voltage
100
90
80
70
60
50
40
30
20 _{4 LEDs AT 9mA/LED}
10 ^VF ^{= 3V}
T_A = 25°C
0
3 3.2 3.4 3.6 3.8 4 4.2 4.4
V_IN (V)
3230 TA01b
3230fa
1