AAT3170_08 Datasheet, PDF (8/15 Pages) Advanced Analogic Technologies – High Current LED Flash Driver Charge Pump IC

ChargePump^TM
Functional Block Diagram
PRODUCT DATASHEET
AAT3170
High Current LED Flash Driver Charge Pump IC
C1+ C1-
C2+ C2-
VIN
Charge Pump
Section 1
1MHz
Oscillator
Soft Start
Control
Charge Pump
Section 2
OUT
F1
EN/SET
System Control;
AS²Cwire;
Timing
F2
GND
CT
Functional Description
The AAT3170 is a high efficiency, low noise, dual stage
tri-mode 1X/1.5X/2X charge pump device intended for
photo-flash LED applications. The AAT3170 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 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 AAT3170 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
battery operating range for 1X and 1.5X modes, improv-
ing efficiency and extending battery life. Each constant
current sink is programmable through the AS²Cwire
serial interface. Independent current settings can be
used for a multistage flash LED control. This feature
allows users to conveniently drive separate dual flash
LEDs directly while achieving good brightness matching.
Also, F1 and F2 can be connected together for single
output configuration.
Modes of Operation
In addition to the data registers that set the current lev-
els for the two current sinks, the AAT3170 has three
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