PRODUCT DATASHEET
AAT3172
ChargePump
TM
Functional Block Diagram
C1+
C1-
C2+
C2-
High Current LED Flash Driver Charge Pump IC
VIN
Charge Pump
Section 1
Charge Pump
Section 2
1MHz
Oscillator
Soft Start
Control
OUT
F1
EN/SET
System Control;
AS
2
Cwire
F2
GND
Functional Description
The AAT3172 is a high efficiency, low noise, dual stage
tri-mode 1X/1.5X/2X charge pump device intended for
photo-flash LED applications. The AAT3172 requires only
four external components: two 1.0µF ceramic capacitors
for the charge pump flying capacitors, one 4.7µF ceram-
ic capacitor for C
IN
, and one 2.2µF ceramic capacitor for
C
OUT
.
The charge pump is designed to deliver load currents up
to 600mA. The dual stage charge pump section contains
soft-start circuitry to prevent excessive in-rush current
during start-up. System efficiency is maximized with a
tri-mode, dual stage charge pump topology. The internal
clock oscillator, which operates at 1MHz, allows the use
of small external components.
The tri-mode charge pump architecture optimizes power
conversion efficiency. Depending upon the combination
of load current, input voltage, and nominal LED forward
voltage, the charge pump will operate in a 1X, 1.5X, or
2X mode to generate the output voltage required to
power the load for a programmed constant current set-
ting. This results in significant power savings over volt-
age doubling architectures, especially when the LEDs are
continuously operated at lower current levels in movie
viewing or flashlight modes.
Constant Current Channels
The AAT3172 contains two programmable constant cur-
rent sinks for integrated flash circuit control. Efficiency is
optimized with the low dropout characteristic of the cur-
rent sinks. The low dropout performance extends the
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