PRODUCT DATASHEET
AAT3104178
ChargePump
TM
Functional Block Diagram
C+
C–
OUT
Low Cost 1x/2x 4 Channel Charge Pump WLED Driver
D1
Two-Mode
CP Control
IN
4
D2
V
F
Monitoring
D3
2x
D4
1x
GND
5
I
REF
EN/SET
S
2
Cwire Control
5 Bits DAC
Functional Description
The AAT3104 is a low-cost charge-pump solution
designed to drive up to four white LEDs. The charge
pump operates from a 2.7V to 5.5V power source and
converts it to voltage levels necessary to drive the LEDs.
LED current is individually controlled through integrated
current sources powered from the output of the charge
pump. Low 1x charge-pump output resistance and low-
drop voltage current sources allow the charge pump to
remain in 1x mode with an input voltage as low as 3.8V
and LED forward voltages of 3.5V. Once in 2x mode, the
charge pump monitors the input supply voltage and
automatically switches back to 1x mode when there is
sufficient input voltage.
The AAT3104 requires only three external components:
one 1μF ceramic capacitor for the charge pump flying
capacitor (C
P
), one 1μF ceramic input capacitor (C
IN
), one
1μF ceramic output capacitor (C
OUT
). The four constant
current outputs of the AAT3104 (D1 to D4) can drive four
individual LEDs with a maximum current of 30mA each.
AnalogicTech’s S
2
Cwire serial interface enables the
AAT3104-1/-2 and changes the current source magni-
tudes through the EN/SET pin.
S
2
Cwire Serial Interface
The LED output current of the AAT3104 is controlled by
AnalogicTech’s S
2
Cwire serial interface. Since the LED
current is programmable, no PWM or additional control
circuitry is needed to control LED brightness. This feature
greatly reduces the burden on a microcontroller or sys-
tem IC to manage LED or display brightness, allowing the
user to “set it and forget it.” With its high-speed serial
interface (1MHz data rate), the LED current can be
changed quickly and easily. Also, the non-pulsating LED
8
www.analogictech.com
3104.2008.09.1.0
ANALOGICTECH [ ADVANCED ANALOGIC TECHNOLOGIES ]
