AAT3192/93
Low-Cost, 2-/3-Channel
Charge-Pump LED Drivers
Functional Block Diagram
C+
C–
OUT
IN
Two-Mode
CP Control
3
D1
D2
V
F
Monitoring
D3
GND
I
REF
EN/SET
(EN/PWM)
S
2
Cwire Control
(PWM Control)
DAC
RSET
Functional Description
The AAT3192 and AAT3193 are low-cost charge-
pump solutions designed to drive up to three 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 indi-
vidually 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 automatically switches back to
1x mode when there is sufficient input voltage.
The AAT3192/93 requires only four external compo-
nents: 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 three constant current outputs of
AAT3193 (D1 to D3) can drive three individual LEDs
with a maximum current of 30mA each. AAT3192 can
drives two constant output sinks (D1 and D2) with up
to 30mA maximum current each. AnalogicTech's
S
2
Cwire serial Interface enables the AAT3192/93-1/
-2/-3 and changes the current sink magnitudes
through the EN/SET pin. The AAT3192/93-4 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
resistor at the RSET pin, the AAT3192/93-1/-2/-4
includes an integrated serial LED current control that
sets the full-scale LED current between 20mA and
0.63mA. For the AAT3192/93-3, a 10.7kΩ external
resistor at the RSET pin sets the fu ll-scale LED cur-
rent 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.
3193.2007.05.1.0
9
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