SC644 Datasheet, PDF (1/26 Pages) Semtech Corporation – Light Management Unit with 4 LDOs and SemPulse®Interface

POWER MANAGEMENT
Features
 Input supply voltage range — 2.9V to 5.5V
 Very high efficiency charge pump driver system with
three modes — 1x, 1.5x, and 2x
 Six programmable current sinks with 29 increments
from 0mA to 25mA
 Four programmable 200mA low-noise LDO regulators
 Programmable driver configurations for main and
sub-display backlight
 Fade-in/fade-out feature for main and sub display
backlight
 SemPulse single wire interface
 Backlight current accuracy — ±1.5% typical
 Backlight current matching — ±0.5% typical
 Automatic sleep mode with LEDs off
 Shutdown current — 0.1µA typical
 Ultra-thin package — 3 x 3 x 0.6 (mm)
 Lead free and halogen free
 WEEE and RoHS compliant
Applications
 Cellular phones, smart phones, and PDAs
 LCD display modules
 Portable media players
 Digital cameras and GPS units
 Display backlighting and LED indicators
SC644
Light Management Unit with
4 LDOs and SemPulse® Interface
Description
The SC644 is a high efficiency charge pump LED driver
using Semtech’s proprietary charge pump technology.
Performance is optimized for use in single cell Li-ion
battery applications.
Display backlighting is provided through six matched
current sinks with integrated fade-in and fade-out con-
trols. The LEDs can be driven as a single set or as two
different sets (for main and sub displays) with indepen-
dent controls. Four low noise, low dropout (LDO) regulators
are provided to supply power for camera module I/O and
other peripheral circuits.
The SC644 uses the proprietary SemPulse® single wire
interface. This interface controls all functions of the device,
including backlight currents and LDO voltage outputs.
The single wire interface minimizes microcontroller and
interface pin counts.
The SC644 enters sleep mode when all the LED drivers are
disabled. In this mode, the quiescent current is reduced
while the device continues to monitor the SemPulse inter-
face. Any combination of LDOs may be enabled when in
sleep mode.
Typical Application Circuit
VBAT = 2.9V to 5.5V
4.7µF
SemPulse
Interface
22nF
October 8, 2009
SC644
IN
OUT
SPIF
BYP
AGND
PGND
BL1
BL2
BL3
BL4
BL5
BL6
LDO1
LDO2
LDO3
LDO4
4.7µF
Main Backlight
Sub
Backlight
VLDO1 = 1.5V to 3.3V
VLDO2 = 1.2V to 1.8V
VLDO3 = 1.5V to 3.3V
1.0µF
1.0µF
1.0µF 1.0µF
Motor
2.2µF
2.2µF
© 2009 Semtech Corporation
US Patents: 6,504,422; 6,794,926