MAX8879 Datasheet, PDF (1/16 Pages) Maxim Integrated Products – Charge Pump for Backlight/Flash/RGB LEDs with Safety Timer

19-4266; Rev 0; 9/08
EVALUATION ^KIT
AVAILABLE
Charge Pump for Backlight/Flash/RGB LEDs
with Safety Timer
General Description
The MAX8879 provides complete light management for
main display backlight, subdisplay backlight (or RGB
indicator), and white LED camera flash with regulated
constant current up to 610mA total. By utilizing adap-
tive 1x/1.5x/2x charge-pump modes and very-low-
dropout current regulators, it achieves high efficiency
over the full 1-cell Li+ battery input voltage range. The
1MHz fixed-frequency switching allows for tiny external
components while the regulation scheme is optimized
to ensure low EMI and low input ripple. An integrated
derating function protects the LEDs from overheating
during high ambient temperatures.
The MAX8879 features an internally trimmed reference
to set the maximum LED current. An I²C serial port is
used for on/off control and setting the LED currents in
32 linear steps for main, sub/RGB, and movie. When
using the RGB indicator, the I²C port provides 32k col-
ors and programmable ramp-up/down rates. The cam-
era flash for flash-mode operation is enabled by an
active-low signal on the FSH pin. A safety timer is acti-
vated on the falling edge of FSH, which has an I²C-
adjustable (programmable) period of no timer, 0.5s,
1.0s, or 2.0s (default). If the safety timer period expires,
both flash and movie modes are disabled.
Applications
Cell Phones and Smartphones
PDAs, Digital Cameras, Camcorders
Displays with Up to 11 LEDs
Features
♦ Guaranteed 610mA Continuous Drive Capability
4 LEDs at 30mA Each for Main Display
3 LEDs at 30mA Each for Sub or RGB
400mA Total for Flash
♦ 2-Wire I²C Serial Port
5-Bit (32-Step) Linear Dimming
32k Colors
Ramp-Up/Down Rates
♦ 92% Peak/83% Avg Efficiency (P_LED/P_BATT)
♦ Adaptive 1x/1.5x/2x Mode Switchover
♦ 0.3% (typ) LED Current Accuracy and Matching
♦ Low Input Ripple and EMI
♦ Low 0.1µA Shutdown Current
♦ Output Overvoltage Protection
♦ I²C Programmable Flash Safety Timer
♦ Thermal Derating Function Protects LEDs
♦ 24-Pin, 4mm x 4mm Thin QFN Package
Ordering Information
PART
TEMP RANGE
PIN-
PACKAGE
MAX8879ETG+
-40°C to +85°C
24 Thin QFN
4mm x 4mm
Pin Configuration appears at end of data sheet.
+Denotes a lead-free/RoHS-compliant package.
Typical Operating Circuit
INPUT
2.7V TO 5.5V
4.7μF
V_LOGIC
0.1μF
I²C PORT
ON/OFF AND
BRIGHTNESS
FLASH
ON/OFF
1μF
1μF
C1P C1N
IN
PIN
C2P C2N
OUTPUT
UP TO 610mA
OUT
10μF
GND
M1
MAX8879
M2
V_DD
M3
M4
S1
S2
SCK
S3
F1
SDA
F2
F3
FSH
F4
PGND
MAIN
SUB OR RGB
FLASH
________________________________________________________________ Maxim Integrated Products 1
For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642,
or visit Maxim’s website at www.maxim-ic.com.