PRODUCT DATASHEET
AAT2860
TM
ChargePump
Backlight/Flash LED Driver and Multiple LDO Lighting Management Unit
Based on the programmed LED current level set by
BL1-BL7 Backlight Control Registers,
REG2, REG3, and REG5
WM[4:0](REG2[D4:D0])and/orWS[4:0](REG3[D4:D0]),
the AAT2860-x increases/decreases linearly from/to the
programmed FLOOR (REG3[D7:D6]) level to/from the
current level set for the MAIN (REG2[D4:D0]) and SUB
(REG3[D4:D0]) groups during LED ON/OFF transitions.
The AAT2860-x’s internal fade response time is approxi-
mately 1 second. In addition, the AAT2860-x provides
four settings selectable over the I2C interface for the fade
function’s LED current floor and these settings are illus-
trated in Table 5.
The AAT2860-x’s I2C registers REG2 and REG3 control
the backlight LED configuration and output current level
in each group of outputs. REG2[D6] (MEQS) defines
whether all seven LED outputs are controlled as a single
group (MEQS = 1 = POR default setting) or are divided
into two sets (by writing a “0” into REG2[D6]) for MAIN/
SUB display applications according to the "Part Number
Descriptions" table.
The default condition for all backlight outputs (BL1-BL5/
BL6/BL7) is OFF after power-up. If the BL1-BL5/BL6/BL7
outputs are grouped together, REG2 Data Bit 5 (MAIN_
ON) is the ON/OFF control for the group; in this case,
REG3[D5] (SUB_ON register bit) is ignored. In the case
of the AAT2860-1, setting MEQS = 0 after POR groups
the BL1-BL4 outputs together as MAIN and groups the
BL5-BL7 outputs as SUB. In this case, REG2[D5] is the
ON/OFF control for the MAIN group and REG3[D5] is the
ON/OFF control for the SUB group.
FL1-FL2 Flash Driver Control Register REG4
Metal-mask options of the base AAT2860-x design have
been configured for backlight and flash/torch applications.
As shown in the "Part Number Descriptions" table, there
are three combinations for backlight and flash available in
this family: the AAT2860-2 (6M+0S+1FL or 4M+2S+1FL),
the AAT2860-3 (6M+0S+1FL or 5M+1S+1FL), or the
AAT2860-4 (5M+0S+2FL or 4M+1S+2FL). The configura-
tion of the LED outputs is controlled by the MEQS bit. In
all cases, the MEQS POR default value of “1” or a user-
programmed value of “0” selects the configuration of the
AAT2860-2/3/4 according to Table 6.
The AAT2860-x LMU also provides an internal LED current
fade function. Fade functionality simply allows for the
turning on/off of the LEDs in a smooth controlled transi-
tion. The AAT2860 does not have to be manually pro-
grammed to avoid the abrupt changes in lighting when
white LED drivers are tuned-on and/or turned-off. The
fade-in/fade-out operation occurs only during LED on/off
transitions. The fade response time is constant regardless
of the LED current level. This feature is useful in those
applications where turning ON/OFF the backlight current
using a smooth transition versus an abrupt ON-to-OFF
transition is preferred. If MEQS = 1(REG2[D6]), then fade
will be disabled in all LED’s when NO_FADE_M(REG5[D1])
is written to 1. In this case, the contents of NO_
FADE_S(REG5[D0]) are ignored. If MEQS = 0, then fade
can be disabled independently for the MAIN and SUB LED
groups using the bits NO_FADE_M and NO_FADE_S.
In all options, the BLX current outputs can be programmed
as a single unit (MEQS = 1) or configured in a MAIN/SUB
arrangement with separate current levels between MAIN
and SUB (MEQS = 0). In the case of the AAT2860-2/3
options where the MEQS bit has been programmed as a
“0,” the BL7 LED output is internally re-configured as a
single flash/lamp current output, FL. In these options, the
maximum available current from the flash output is 600mA
(see Table 7) and maximum available current for torch or
flash inhibit is 120mA (see Table 9). For the AAT2860-4,
the BL6 and the BL7 outputs are internally reconfigured as
flash current outputs, FL1 and FL2, respectively, where
each flash output is capable of supplying up to 300mA in
full-flash mode and up to 60mA in torch mode.
w w w . a n a l o g i c t e c h . c o m
2860.2008.05.1.0
15
ANALOGICTECH [ ADVANCED ANALOGIC TECHNOLOGIES ]
