SC657
Backlight Driver for 5 LEDs
with SemPulseTM Interface
POWER MANAGEMENT
Features
Description
Input supply voltage range — 2.9V to 5.5V
Very high efficiency charge pump driver system with
three modes — ꢀx, ꢀ.5x and 2x
Five programmable current sinks — 0mA to 25mA
Up to three LED grouping options
Fade-in/fade-out feature for main LED bank
Charge pump frequency — 250kHz
SemPulse single wire interface
Backlight current accuracy — ꢀ.5% typical
Backlight current matching — 0.5% typical
LED float detection
The SC657 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.
The charge pump provides backlight current utilizing five
matched current sinks. The load and supply conditions
determine whether the charge pump operates in ꢀx, ꢀ.5x,
or 2x mode. An optional fading feature that gradually
adjusts the backlight current is provided to simplify
control software.
Automatic sleep mode (LEDs off) — IQ = 60µA (typ.)
Shutdown current — 0.ꢀµA (typical)
Ultra-thin package — 2 x 2 x 0.6 (mm)
Fully WEEE and RoHS compliant
The SC657 uses the proprietary SemPulseTM single wire
interface to control all functions of the device, including
backlight currents. The single wire interface minimizes
microcontroller and interface pin counts. The five LEDs
can be grouped in up to three separate banks that can be
independently controlled.
Applications
Cellular phones, smart phones, and PDAs
LCD modules
Portable media players
Digital cameras
Personal navigation devices
Display/keypad backlighting and LED indicators
The SC657 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
interface.
With a 2 x 2 (mm) package and four small capacitors, the
SC657 provides a complete LED driver solution with a
minimal PCB footprint.
Typical Application Circuit
VBAT = 2.9 to 5.5V
IN
OUT
COUT
CIN
2.2µF
2.2µF
SC657
BL1
BL2
BL3
BL4
BL5
SemPulse
Interface
SPIF
GND
C1+ C1- C2+ C2-
C1
2.2µF
C2
2.2µF
US Patents: 6,504,422; 6,794,926
ꢀ
April 3, 2009
© 2009 Semtech Corporation