PRODUCT DATASHEET
AAT2861
TM
ChargePump
Backlight/Flash LED Driver and Multiple LDO Lighting Management Unit
For example, a change from 28mA to 8mA in the Main
backlight channels should follow this procedure. First,
Sub Backlight
Address
Data
Address
Data
Sub Current
28mA is set by programming Data = 3 to Address 2 and
Data=1 to Address 3. When changing to 8mA first write
Data=2 to Address 3. The current level will not change
after this step. Then write Data=7 to Address 2. After
Address 2 has been latched the new 8mA current level
will be set.
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
1
1
1
1
1
1
1
1
1
1
1
1*
1
1
1
1
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
1
2
3
4
5
6
7
8
9
10
11
12*
13
14
15
16
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
31
30
29
28
27
26
25
24
23
22
21
20*
19
18
17
16
15
14
13
12
11
10
9
Address 3 also controls the “Main Equals Sub” feature in
the AAT2861 products. This feature allows all backlight
channels to be controlled with only the Main Channel
current settings. If the “Main Equals Sub” feature is
turned on (Data 3, or 4 in Address 3) the current set-
tings of the Sub Channel are ignored. All backlight chan-
nels will be set to the same current levels as determined
by the Data programmed to “Backlight Current Main” in
Addresses 2 and 3. The Main and Sub channels are
turned on and off by the “Main On” setting in Address 0.
The default condition is for the “Main Equals Sub” feature
to be turned OFF (MEQS=0) after power-up.
Table 6 shows the Main and Sub Channel Configurations
for the three versions of the AAT2861. The effect of the
“Main Equals Sub” feature is clearly represented in this
table.
8
7
6
5
4
3
2
1
Main Equals Sub (IMAIN = ISUB
)
Part Number
Yes (Default)
No
AAT2861-1
AAT2861-2
AAT2861-3
7M+0S+1FL
6M+0S+2FL
7M+0S+1FL
4M+3S+1FL
4M+2S+2FL
5M+2S+1FL
0.5
Table 6: Main and Sub Channel Configurations.
Table 5: Backlight Sub Current Control
(Addresses 4 and 5).
LDO Output Voltage Control
(Addresses 6 to 9)
The current settings for the Main and Sub channels are
each divided into two Addresses. Any change in Data to
the “Backlight Current Main (or Sub), LSB’s” Address will
result in an immediate change to the LED current output
level. Programming new current settings that require a
change to both “Backlight Current Main (or Sub), MSB”
and “Backlight Current Main (or Sub), LSB’s” Addresses
could result in an errant intermediate current setting. To
avoid this problem when the Data in “Backlight Current
Main (or Sub), MSB” Address is changed the new current
setting will not take effect until “Backlight Current Main
(or Sub), LSB’s” Address has been written to and
latched.
The AAT2861’s three LDO regulators are configured by
programming Addresses 6, 7, 8, and 9 via the AS2Cwire
interface. With the EN/SET pin pulled high and the
AAT2861 turned on, LDOA can be enabled using the EN_
LDOA pin. LDOB and LDOC can be enabled together using
the EN_LDOB/C pin. Additional LDO regulator control can
be achieved using Address 6 to override the enable com-
mand of the EN_LDOA and EN_LDOB/C pins. For example,
with the EN_LDOA and EN_LDOB/C pins enabled, writing
Data 5 to Address 6 will disable LDOB and leave LDOA and
LDOC enabled. Table 7 shows the LDO disable control.
Writing data to Addresses 7, 8, and 9 set the output volt-
ages for LDOA, LDOB, and LDOC to one of 16 levels. The
available LDO output voltages are shown in Table 8.
w w w . a n a l o g i c t e c h . c o m
2861.2009.02.1.2
17
AAT [ ADVANCED ANALOG TECHNOLOGY, INC. ]
