SC621A
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
Flash LED — 400mA max in flash mode, 250mA max
continuous for spotlight
Two user-configurable 100mA low-noise LDO
regulators
Charge pump frequency — 250kHz
I
2
C compatible interface —
up to 400kHz
Backlight current accuracy ±1.5% typical
Backlight current matching ±0.5% typical
Programmable fade-in/fade-out for main backlight
External flash control pin to sync with camera
Optional 1s flash time out
Automatic sleep mode (LEDs off )
—
I
Q
= 100μA
Low shutdown current — 0.1μA (typical)
Ultra-thin package — 3mm x 3mm x 0.6mm
Fully WEEE and RoHS compliant
Charge Pump, 4 LEDs, 400mA Flash LED,
Dual LDOs, and I
2
C Interface
Description
The SC621A 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. It also can
supply continuous or bursted current to a flash LED using
the dedicated flash driver current sink. 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. A flash-timeout feature disables
the flash if active for longer than 1 second. The SC621A also
provides two low-dropout, low-noise linear regulators for
powering a camera module or other peripheral circuits.
The SC621A uses an I
2
C compatible serial interface. The
interface controls all functions of the device, including
backlight and flash currents as well as two LDO voltage
outputs. The flash/spotlight output is triggered via either
the I
2
C interface or a dedicated pin.
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 and flash
PDA backlighting and flash
Camera I/O and core power
Typical Application Circuit
MAIN BACKLIGHT
V
BAT
C
IN
2.2μF
VIN
I
2
C Data
I C Clock
Flash Control
Enable Control
2
FLASH
VOUT
SDA
SCL
FLEN
EN
BYP
SC621A
BL
1
BL
2
BL
3
BL
4
FL
LDO
1
LDO
2
C1-
C2+ C2-
C2
2.2μF
C
OUT
4.7μF
C
BYP
22nF
AGND
PGND
C1+
C1
2.2μF
V
LDO1
= 2.5V to 3.3V
V
LDO2
= 1.5V to 1.8V
C
LDO1
1μF
C
LDO2
1μF
US Patents: 6,504,422; 6,794,926
June 27, 2007
© 2007 Semtech Corporation
1
SEMTECH [ SEMTECH CORPORATION ]
