SC658 Datasheet, PDF (1/22 Pages) Semtech Corporation – Backlight Driver for 4 LEDs with SemPulseTM Interface

SC658
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
 Four 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 — ±1.5% typical
 Backlight current matching — ±0.5% typical
 LED float detection
 Automatic sleep mode (LEDs off ) — I_Q = 60µA (typ.)
 Shutdown current — 0.1µA (typical)
 Ultra-thin package — 2 x 2 x 0.6 (mm)
 Fully WEEE and RoHS compliant
Applications
 Cellular phones, smart phones, and PDAs
 LCD modules
 Portable media players
 Digital cameras
 Personal navigation devices
 Display/keypad backlighting and LED indicators
Backlight Driver for 4 LEDs
with SemPulse^TM Interface
Description
The SC658 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 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 SC658 uses the proprietary SemPulse^TM single wire
interface to control all functions of the device, including
backlight currents. The single wire interface minimizes
microcontroller and interface pin counts. The four LEDs
can be grouped in up to three separate banks that can be
independently controlled.
The SC658 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
SC658 provides a complete LED driver solution with a
minimal PCB footprint.
Typical Application Circuit
V_BAT = 2.9 to 5.5V
C_IN
2.2µF
From
Microprocessor
IN
OUT
SC658
BL1
SPIF
BL2
BL3
BL4
C_OUT
2.2µF
April 3, 2009
GND
C1+ C1- C2+ C2-
C1
2.2µF
C2
2.2µF
© 2009 Semtech Corporation
US Patents: 6,504,422; 6,794,926