AAT2847
Four-Channel Backlight Driver with Dual LDOs
Current Scale (Address 3)
Low Current Operation (Address 4)
The AAT2847 has three selectable current scales for
the four white LED channels: 30mA, 20mA, and
15mA. Only one of the three current scales can be
active at any given time. By default, the 20mA current
scale is active upon start-up. To change to the 30mA
or 15mA current scale, or go back to the 20mA scale,
write toAddress 3 with the appropriate Data between,
and including, 1 to 3. To enable low current mode,
write Data 4 to Address 3. Low current mode results
in the four white LED channels reverting to the cur-
rent set by the low current settings in Address 4.
All four LED channels are programmed to the same
low current level by writing to Address 4 followed by
any Data between, and including, 1 to 4. This oper-
ational mode is especially useful for low current
applications where a continuous low current state
is maintained for a substantial length of time.
Data
mA
0.5
1.0
1.5
2.0
1
2
3
4
Data 30mA Scale 20mA Scale 15mA Scale
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
30.0
28.5
26.6
25.2
23.3
21.8
19.8
18.5
16.5
15.0
13.1
11.6
9.8
20.0
19.0
17.7
16.8
15.5
14.5
13.2
12.3
11.0
10.0
8.7
15.0
14.3
13.3
12.6
11.6
10.9
9.9
9.2
8.3
7.5
6.5
Table 4: Low Current Settings—Address 4.
Independent LED Current Control
(Address 5)
Independent LED control allows for individual LEDs
to be enabled and disabled to form custom
arrangement of active LEDs. To enable independ-
ent control write Address 5 with Data between, and
including, 1 to 16.
Data
D4
D3
D2
D1
7.7
6.5
5.5
4.2
5.8
4.9
4.1
3.2
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
on
on
on
on
on
on
on
on
off
off
off
off
off
off
off
off
on
on
on
on
off
off
off
off
on
on
on
on
off
off
off
off
on
on
off
off
on
on
off
off
on
on
off
off
on
on
off
off
on
off
on
off
on
off
on
off
on
off
on
off
on
off
on
off
8.3
6.3
4.8
3.2
2.4
Table 2: Current Settings—Address 0.
Data
Current Scale
20mA Scale
30mA Scale
15mA Scale
Low Current Mode
1
2
3
4
Table 3: Current Scale Settings—Address 3.
Table 5: Independent LED Control Settings—
Address 5.
2847.2007.09.1.0
13
ANALOGICTECH [ ADVANCED ANALOGIC TECHNOLOGIES ]
