AAT2856INJ-EE-T1 Advanced Analog Technology, Inc., AAT2856INJ-EE-T1 Datasheet - Page 10

• Manufacturer Part Number: AAT2856INJ-EE-T1
• Description: High Current Charge Pump with Dual LDO for Backlight Applications
• Manufacturer: Advanced Analog Technology, Inc.

The AAT2856 incorporates additional circuitry that opti-
mizes performance for exceptionally low backlight cur-
rent settings. A separate address is used to activate this
circuitry. To program the low current settings with
improved performance and efficiency, write to Address
3. Unlike Addresses 0-2, which have current level set-
tings according to Table 2 and Figure 2, Address 3 pos-
sesses a separate set of current levels described by the
Low Current Backlight settings found in Table 3.
10
ChargePump
Data
Data
Table 2: Data for the Backlight Current Level,
10
11
12
13
14
15
16
10
11
12
13
14
15
16
1
2
3
4
5
6
7
8
9
1
2
3
4
5
6
7
8
9
Table 3: Low-Level Backlight Current,
Main Current
30mA Max (mA)
Address 3, FS = 20mA Range.
On
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
No
No
No
No
No
No
No
No
TM
30.0
27.9
26.1
24.2
21.0
19.2
17.3
15.0
12.7
10.9
8.1
6.2
4.4
3.5
2.6
0
Addresses 0-3.
High Current Charge Pump with Dual LDO for Backlight Applications
Sub Current
20mA Max (mA)
On
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
No
No
No
No
No
No
No
No
20.0
19.0
17.8
16.5
14.3
13.0
11.8
10.2
8.5
7.3
5.4
4.1
2.9
2.2
1.6
0
w w w . a n a l o g i c t e c h . c o m
Current
(μA)
1900
1900
1900
500
950
500
950
500
950
95
95
95
0
0
0
0
Maximum Backlight Current
(Address 12)
There are two separate current level scales that apply to
Addresses 0-2: 20mA and 30mA. According to the
Maximum Backlight Current setting at Address 12, only
one of the two scales can be active at any given time
and never both. By default, the 20mA scale is active on
startup. To change to the 30mA scale, or go back to the
20mA scale, write to Address 12.
Since only one of the scales can be active at any given
time, the 20mA and 30mA scales cannot be mixed
between main and sub. When setting Address 12 to the
30mA scale, only current levels from that scale can be
mixed between main and sub. When changing maximum
current scales, the data remains constant regardless of
scale. When the maximum current scale is changed, the
previously stored data value will remain constant but the
current value will change due to the different current
values on the separate maximum current scales.
Backlight Independent Channel Control
(Address 15)
The AAT2856 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.
Table 4: Address 12 Maximum Current Scale.
Data
Figure 2: Data Code for Address 0-3 vs.
1
2
35
30
25
20
15
10
5
0
1
2
Backlight Current Level.
20mA FS
3
4
30mA FS
PRODUCT DATASHEET
5
Maximum Current Scale
6
7
Data Code
8
AAT2856
9
10 11 12 13 14 15 16
20mA
30mA
2856.2008.02.1.3