AAT2846_08 Datasheet, PDF (12/22 Pages) Advanced Analogic Technologies – High Current Charge Pump with Dual LDO for Backlight and Flash Applications

PRODUCT DATASHEET
AAT2846
ChargePump^TM High Current Charge Pump with Dual LDO for Backlight and Flash Applications
Flash Current FL1, FL2 (Address 4)
The current level for the flash channels FL1 and FL2 is
programmed by Address 4. Data 1 enables the maximum
current level. The maximum current level is determined
by the value of R_FSET. Table 4 and Figure 3 illustrate the
additional flash current levels that are available.
Data
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
Flash LED Current
(% of Maximum)
100
87
77
66
58
50
44
39
35
30
27
24
20
17
16
14
Table 4: Data Code for the Flash Current Control,
Address 4.
120
I_FLED = 100%
100
at Data 1
80
60
I_FLED = 14%
40
at Data 16
20
0
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16
Data Code
Figure 3: Data Code for Address 4 vs.
Percentage of Flash Current Level.
Independent Flash ON/OFF Control
(Address 5)
Use Address 5 to program which flash channels are
active. By default, both flash channels are OFF at start-
up. After writing to Address 4 to program the desired
flash channel current level, write to Address 5 to enable
a single channel or both channels according to Table 5.
Data
1
2
3
4
FL1
Off
Off
On
On
FL2
Off
On
Off
On
Table 5: Output Enable Control, Address 5.
Writing to Address 5 enables the flash channels indefi-
nitely. FL1 and FL2 will remain ON until Address 5 is
re-programmed to OFF, ENS is strobed low to shutdown
the device, or the flash safety timer times out after FEN
has been strobed high. The flash safety timer is always
activated when FEN is taken high. The Address 5 data
setting is always reset to Data 1 when the flash timer
expires or when FEN is strobed low.
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.
Data
1
2
Maximum Current
20mA
30mA
Table 6: Data Code for the Maximum Current
Settings, Address 12.
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.
12
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2846.2008.03.1.1