LTC3205_15 Datasheet, PDF (1/16 Pages) Linear Technology – Multidisplay LED Controller

LTC3205
Multidisplay
LED Controller
FEATURES
s _{Step-Up/Step-Down Fractional Charge Pump for Up}
to 92% Efficiency
s _{Independent Current and Dimming Control for}
1-4 LED Main, 1-2 LED Sub and RGB LED Displays
s _{LED Currents Programmable Using 3-Wire Serial}
Interface
s _{Up to 250mA of Continuous LED Current}
s _{0.7% LED Current Matching}
s _{Low Noise Constant Frequency Operation*}
s _{Minimal Component Count}
s _{Automatic Soft-Start Limits Inrush Current}
s _{Four Programmable Dimming States for Main and}
Sub Displays
s _{Up to 4096 Color Combinations for RGB Display}
s _{Low Shutdown Current: ICC < 1µA}
s _{Tiny 24-Lead (4mm × 4mm) QFN Package}
U
APPLICATIO S
s _{Cellular Phones}
s _{Wireless PDAs}
s _{Multidisplay Handheld Devices}
, LTC and LT are registered trademarks of Linear Technology Corporation.
* U.S. Patent 6,411,531
DESCRIPTIO
The LTC^®3205 is a highly integrated multidisplay LED con-
troller. The part contains a high efficiency, low noise frac-
tional step-up/step-down charge pump to provide power
for both main and sub white LED displays plus an RGB
color LED display. The LTC3205 requires only four small
ceramic capacitors plus two resistors to form a complete
3-display LED power supply and current controller.
Maximum currents for the main/sub and RGB displays are
set independently with a single resistor. Current for each
LED is controlled with an internal current source. Dim-
ming and ON/OFF control for all displays are achieved via
a 3-wire serial interface. Four dimming states exist for the
main and sub displays and 16 dimming states are available
via internal PWM for the red, green and blue LEDs result-
ing in up to 4096 color combinations.
The LTC3205 charge pump optimizes efficiency based on
V_IN and LED forward voltage conditions. The part powers
up in step-down mode and automatically switches to step-
up mode once any enabled LED current source begins to
enter dropout. Internal circuitry prevents inrush current and
excess input noise during start-up and mode switching.
The LTC3205 is available in a low profile 24-lead
(4mm × 4mm × 0.8mm) QFN package.
TYPICAL APPLICATIO
1µF
1µF
V_IN
2.8V TO
4.5V
V_IN
CPO
1µF
LTC3205
SERIAL 3
INTERFACE
4
MAIN1-4
2
SUB1-2
3
SERIAL PORT RGB
I_RGB
I_MS
MAIN DISPLAY
SUB DISPLAY
RGB ILLUMINATOR
1µF
RED GREEN BLUE
3205 TA01a
4-LED Main Panel Efficiency
vs Input Voltage
100
90
80
70
60
50
40
30
20 _{FOUR LEDs AT 15mA/LED}
10 ^{(TYP V}F ^{AT 15mA = 3.2V)}
T_A = 25°C
0
3.0
3.3
3.6
3.9
4.2
INPUT VOLTAGE (V)
3205 TA01b
3205f
1