SC668 Datasheet, PDF (1/46 Pages) Semtech Corporation – 8 LED Light Management Unit Automatic Dropout Prevention , Ambient Light Sense Input, PWM Dimming, and 4 LDOs

POWER MANAGEMENT
SC668
8 LED Light Management Unit
Automatic Dropout Prevention , Ambient Light
Sense Input, PWM Dimming, and 4 LDOs
Features
Description
 Eight LED backlight sinks with 32 current settings
The SC668 is a highly integrated light management unit
from — 0mA to 25mA
that provides programmable current for up to eight LED
 Up to four LED backlight banks
current sinks. Four LED banks are provided to allow set-
 Lighting effects — fade-in/fade-out, breathe, blink,
tings for various LED zones or indicators. Four low-noise
auto-dim full, and auto-dim partial functions
LDOs with programmable outputs ranging from 1.2V to 3.3V
 ADP (Automatic Dropout Protection) for backlights
and 200mA maximum output current are also included.
 ALS (Ambient Light Sense) option sets the backlight
brightness according to ambient lighting conditions
ADP limits the maximum LED current to a level that ensures
 I²C Bus fast mode and standard mode
the LEDs maintain matched currents when the supply
 Backlight current accuracy — ± 1.5% typical
voltage approaches dropout. This feature produces accept-
 Backlight current matching — ± 0.5% typical
able light output at low supply voltage levels without
 Four programmable 200mA low-noise LDO regulators ^{requiring a boost converter or charge pump.}
 PWM interface (200Hz to 50kHz) with internal digital
low-pass filter
 Automatic sleep mode with all 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
Two interfaces are provided for design flexibility. The I²C
interface controls the LED on/off functions, assigns the
LEDs to backlight banks, programs the LED currents, pro-
grams the lighting effects, enables the LDOs, and sets the
LDO output voltages. The PWM interface reduces the
current setting for LED bank #1 by a factor equal to the duty
cycle of the applied PWM signal. A filter at the PWM input
converts the pulsed signal to a DC current level, resulting in
 Cellular phones, smart phones, and PDAs
less switching noise compared to pulsed current methods.
 LCD modules
 Portable media players and digital cameras
 Personal navigation devices
 Display/keypad backlighting and LED indicators
The ADI input translates the voltage from an external ALS
(Ambient Light Sensor) into a digitized code using a sigma-
delta ADC. This block includes level detection to adjust the
current setting of bank #1 with two different programmable
levels based on the ambient light level. An interrupt output
transitions low to notify the host processor that a level
adjustment has been made.
Typical Application Circuit
2.9 to 5.5V
VIN
VIN
IN ^SC668 BL1
CIN
BL2
RSDA
RSCL
GND
BL3
BL4
I²C Data
SDA
BL5
I²C Clock
Backlight PWM
Device Enable
VLDO4
SCL
PWM
EN
ADI
BYP
BL6
BL7
BL8
LDO1
LDO2
LDO3
LDO4
LDO1
LDO2
LDO3
LDO4
CBYP
C1
C2
C3
C4
Ambient Light Sensor
May 24, 2010
© 2010 Semtech Corporation