AAT2846
High Current Charge Pump with Dual LDO
for Backlight and Flash Applications
Backlight Independent Channel Control
(Address 15)
The AAT2846 has a unique independent channel
control mode whereby individual backlight LED
channels can be enabled and disabled to form a
custom arrangement of active channels.
Data
1
2
3
4
5
6
7
8
BL6
BL5
BL4
BL3
Off
Off
Off
Off
Off
Off
Off
Off
On
On
On
On
On
On
On
On
Off
Off
Off
Off
On
On
On
On
Off
Off
Off
Off
On
On
On
On
Off
Off
On
On
Off
Off
On
On
Off
Off
On
On
Off
Off
On
On
Off
On
Off
On
Off
On
Off
On
Off
On
Off
On
Off
On
Off
On
To enable independent channel control mode, write
Data 8 to Address 15. To exit individual mode con-
trol, the AAT2846 state machine can be reset by
strobing ENS low and holding ENS low longer than
9
2
the A SCwire's tOFF latch time.
10
11
12
13
14
15
16
Data
Individual Backlight Control
8
On
Table 7: Data Code for Independent
Backlight Control, Address 15.
With independent channel control mode enabled,
Addresses 2 and 3 are re-mapped according to
Tables 8 and 9. As indicated by the possible set-
tings listed in the tables, any combination of back-
lighting channels can be enabled and disabled.
Table 8: Data Code for BL3-BL6
On/Off Control, Sub-Address 2.
Data
BL2
BL1
Because Addresses 2 and 3 are re-mapped when
independent channel control mode is enabled, the
functions originally assigned to Addresses 2 and 3
are no longer available.
It is also important to note that Address 0 is dis-
abled when independent channel control mode is
enabled. Additionally, Address 3 is disabled and the
very low current settings cannot be used in this
mode. Other addresses are unmodified by this
mode so that the flash features can still be operat-
ed and the 30mA backlight scale can still be used.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
Off
Off
Off
Off
Off
Off
Off
Off
On
On
On
On
On
On
On
On
Off
Off
Off
Off
On
On
On
On
Off
Off
Off
Off
On
On
On
On
The LDO enables are always independent of
2
AS Cwire programming.
Flash LED Current Control
The flash LEDs are driven through current sinks
FL1 and FL2. There are two ways to drive the flash
2
Table 9: : Data Code for BL1 and BL2
On/Off Control, Sub-Address 3.
LEDs: either through the AS Cwire serial interface
or through the flash enable input, FEN. The
AAT2846 also includes an adjustable safety timer
to turn off the flash in the event of a controller fault
to prevent overstressing the flash LEDs.
Flash/Movie Mode Operation
The flash LED current level is set via the serial inter-
face according to a logarithmic scale where each
code is 1.2dB lower than the previous code as a per-
2846.2007.08.1.0
15
ANALOGICTECH [ ADVANCED ANALOGIC TECHNOLOGIES ]
