PRODUCT DATASHEET
AAT3192
ChargePump
TM
2-Channel Charge-Pump LED Driver
Functional Block Diagram
C+
C-
OUT
Two-Mode
CP Control
IN
V
F
Monitoring
2
D1
D2
GND
I
REF
EN/SET
(EN/PWM
)
S
2
Cwire Control
(PWM Control)
DAC
RSET
Functional Description
The AAT3192 is a low-cost charge-pump solution designed
to drive up to two white LEDs. The charge pump oper-
ates 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 sinks
powered from the output of the charge pump. Low 1x
charge-pump output resistance and low-drop voltage
current sinks allow the charge pump to stay in 1x mode
with an input voltage as low as 3.75V and LED forward
voltages as high as 3.5V. Once in 2x mode, the charge
pump monitors the input supply voltage and automati-
cally switches back to 1x mode when there is sufficient
input voltage.
The AAT3192 requires only four external components:
one 1μF ceramic capacitor for the charge pump flying
capacitors (C
P
), one 1μF ceramic input capacitor (C
IN
),
one 1μF ceramic output capacitor (C
OUT
) and a resistor
(R
SET
) to set the maximum LED current. The AAT3192
can drive two constant output sinks (D1 and D2) with up
to 30mA maximum current each. AnalogicTech’s S
2
Cwire
serial interface enables the AAT3192-1/-2/-3 and chang-
es the current sink magnitudes through the EN/SET pin.
The AAT3192-4 uses an external PWM signal to enable
the IC and control the brightness of the LEDs.
Constant Current Control using R
SET
The maximum current is programmed by an external
resistor at the RSET pin. Using a 14.3kΩ external resis-
tor at the RSET pin, the AAT3192-1/-2/-4 includes an
integrated serial LED current control that sets the full-
scale LED current between 20mA and 0.63mA. For the
AAT3192-3, a 11.5kΩ external resistor at the RSET pin
sets the full-scale LED current between 20mA and
1.3mA. The full-scale LED current can set higher or lower
than 20mA; see Table 5. For maximum accuracy, a 1%
tolerance resistor is recommended.
3192.2008.07.1.3
www.analogictech.com
9
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