AAT3152
High Efficiency 1X/1.5X/2X Charge Pump
For White LED Applications
Functional Block Diagram
C1+
C1- C2+
C2-
VIN
1X, 1.5X and 2X
Charge Pump
VOUT
Soft-Start
Control
1MHz
Oscillator
Voltage
Reference
D/A
6 x 16 bit
ROM
D/A
D/A
D1
D2
D3
EN/SET
S
2
C
Interface
6 x 16 bit
ROM
D/A
D4
GND
Functional Description
The AAT3152 is a tri-mode load switch (1X) and
high efficiency (1.5X or 2X) charge pump device
intended for white LED backlight applications. To
maximize power conversion efficiency, an internal
sensing circuit monitors the voltage required on
each constant current sink input and sets the load
switch and charge pump modes based on the input
battery voltage and the current sink input voltage.
As the battery discharges over time, the AAT3152
charge pump is enabled when any of the four cur-
rent sink inputs near dropout. The charge pump ini-
tially starts in 1.5X mode. If the charge pump out-
put drops enough for any current source output to
become close to dropout, the charge pump will
automatically transition to 2X mode. The AAT3152
requires only four external components: two 1µF
ceramic capacitors for the charge pump flying
capacitors (C1 and C2), one 1µF ceramic input
capacitor (C
IN
), and one 0.33µF to 1µF ceramic
charge pump output capacitor (C
OUT
).
The four constant current sink inputs (D1 to D4)
can drive four individual LEDs with a maximum cur-
rent of 20mA each. The unused sink inputs must be
connected to V
OUT
, otherwise the part will operate
only in 2X charge pump mode. The S
2
Cwire serial
interface enables the AAT3152 and sets the cur-
rent sink magnitudes. S
2
Cwire addressing allows
independent control of two groups of current sink
input: D1-D3 and D4.
6
3152.2004.12.0.9
ANALOGICTECH [ ADVANCED ANALOGIC TECHNOLOGIES ]
