PRODUCT DATASHEET
AAT2861
TM
ChargePump
Backlight/Flash LED Driver and Multiple LDO Lighting Management Unit
Data
FL1
BL7/FL2
BL6
BL5
1*
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
Conditionally ON*
Conditionally ON
Conditionally ON
Conditionally ON
Conditionally ON
Conditionally ON
Conditionally ON
Conditionally ON
OFF
Conditionally ON *
Conditionally ON
Conditionally ON
Conditionally ON
OFF
Conditionally ON*
Conditionally ON
OFF
Conditionally ON*
OFF
Conditionally ON
OFF
Conditionally ON
OFF
Conditionally ON
OFF
Conditionally ON
OFF
Conditionally ON
OFF
Conditionally ON
OFF
Conditionally ON
OFF
OFF
Conditionally ON
Conditionally ON
OFF
OFF
OFF
OFF
OFF
Conditionally ON
Conditionally ON
Conditionally ON
Conditionally ON
OFF
Conditionally ON
Conditionally ON
OFF
OFF
OFF
OFF
OFF
OFF
OFF
OFF
OFF
Conditionally ON
Conditionally ON
OFF
OFF
OFF
OFF
OFF
Table 12: LED Channel Individual Disable Control, BL5, BL6, BL7/FL2, FL1 (Address 13).
Device Switching Noise Performance
Applications Information
The AAT2861 operates at a fixed frequency of approxi-
LED Selection
mately 1MHz to control noise and limit harmonics that
can interfere with the RF operation of cellular telephone
handsets or other communication devices. Back-injected
noise appearing on the input pin of the charge pump is
20mV peak-to-peak, typically ten times less than induc-
tor-based DC/DC boost converter white LED backlight
solutions. The AAT2861 soft-start feature prevents noise
transient effects associated with in-rush currents during
the start up of the charge pump circuit.
The AAT2861 is specifically intended for driving white
LEDs. However, the device design will allow the AAT2861
to drive most types of LEDs with forward voltage speci-
fications ranging from 2.0V to 4.7V. LED applications
may include mixed arrangements for display backlight-
ing, color (RGB) LEDs, infrared (IR) diodes and any
other load needing a constant current source generated
from a varying input voltage. Since the BL1 to BL6, BL7/
FL2 and FL1 constant current sinks are matched with
negligible voltage dependence, the constant current
channels will be matched regardless of the specific LED
forward voltage (VF) levels.
Device Power Efficiency
Charge-pump efficiency discussion in the following sec-
tions accounts only for the efficiency of the charge pump
section itself. Due to the unique circuit architecture and
design of the AAT2861, it is very difficult to measure
efficiency in terms of a percent value comparing input
power over output power.
The low-dropout current sinks in the AAT2861 maximize
performance and make it capable of driving LEDs with
high forward voltages. Multiple channels can be com-
bined to obtain a higher LED drive current without com-
plication.
*Denotes default (power-on-reset) value.
w w w . a n a l o g i c t e c h . c o m
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2861.2009.02.1.2
AAT [ ADVANCED ANALOG TECHNOLOGY, INC. ]
