SC624
LED Light Management Unit
POWER MANAGEMENT
Features
Input supply voltage range — 3.0V to 5.5V
Charge pump modes — 1x, 1.5x and 2x
Four programmable current sinks with 32 steps from
0.5mA to 25mA
Two programmable 200mA low-noise LDO regulators
Charge pump frequency — 250kHz
SemWire
TM
single wire interface —
up to 75kbit/s
Backlight current accuracy ±1.5% typical
Backlight current matching ±0.5% typical
Programmable fade-in/fade-out for main backlight
Automatic sleep mode (LEDs off )
—
I
Q
= 100μA
Low shutdown current — 0.1μA (typical)
Ultra-thin package — 3mm x 3mm x 0.6mm
Lead-free and halogen-free
WEEE and RoHS compliant
Charge Pump, 4 LEDs, Dual LDOs,
and SemWire
TM
Interface
Description
The SC624 is a high efficiency charge pump LED driver
using Semtech’s proprietary mAhXLife
TM
technology.
Performance is optimized for use in single-cell Li-ion
battery applications.
The charge pump provides backlight current in
conjunction with four matched current sinks. The load
and supply conditions determine whether the charge
pump operates in 1x, 1.5x, or 2x mode. An optional fading
feature that gradually adjusts the backlight current is
provided to simplify control software. The SC624 also
provides two low-dropout, low-noise linear regulators for
powering a camera module or other peripheral circuits.
The SC624 uses the proprietary SemWire
TM
single wire
interface. The interface controls all functions of the device,
including backlight current and two LDO voltage outputs.
The single wire implementation minimizes microcontroller
and interface pin counts.
In sleep mode, the device reduces quiescent current to
100μA while continuing to monitor the serial interface.
The two LDOs can be enabled when the device is in sleep
mode. Total current reduces to 0.1μA
in shutdown.
Applications
Cellular phone backlighting
PDA backlighting
Camera I/O and core power
Typical Application Circuit
MAIN BACKLIGHT
V
BAT
C
IN
1μF
SemWire
Interface
VIN
SWIF
VOUT
C
OUT
2.2μF
BL1
BL2
BL3
BL4
LDO1
LDO2
C2+ C2-
C2
1μF
C
LDO1
1μF
V
LDO1
= 2.5V to 3.3V
V
LDO2
= 1.5V to 1.8V
C
LDO2
1μF
SC624
BYP
C
BYP
22nF
GREF
AGND
PGND
C1+ C1-
C1
1μF
US Patents: 6,504,422; 6,794,926
October 20, 2009
© 2009 Semtech Corporation
1
SEMTECH [ SEMTECH CORPORATION ]
