AAT3172 Datasheet, PDF (8/14 Pages) Advanced Analogic Technologies – High Current LED Flash Driver Charge Pump IC

AAT3172
High Current LED Flash Driver Charge Pump IC
Functional Block Diagram
VIN
C1+ C1-
Charge Pump
Section 1
2MHz
Oscillator
Soft Start
Control
EN/SET
System Control;
AS²Cwire
C2+ C2-
Charge Pump
Section 2
OUT
F1
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 ceramic capacitor for
C_IN, and one 2.2µF ceramic capacitor for C_OUT.
The charge pump is designed to deliver continuous
load currents up to 400mA. For short duration flash
events, the AAT3172 can deliver peak load cur-
rents up to 600mA over a 0°C to 70°C operating
temperature range. 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 oscilla-
tor, which operates at 2MHz, 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 pro-
grammed constant current setting. This results in
significant power savings over voltage doubling
architectures, especially when the LEDs are con-
tinuously operated at lower current levels in movie
viewing or flashlight modes.
Constant Current Channels
The AAT3172 contains two programmable constant
current sinks for integrated flash circuit control.
Efficiency is optimized with the low dropout char-
acteristic of the current sinks. The low dropout per-
formance extends the battery operating range for
1X and 1.5X modes, improving efficiency and
extending battery life. Each constant current sink is
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