AAT2846 Datasheet, PDF (14/25 Pages) Advanced Analogic Technologies – High Current Charge Pump with Dual LDO for Backlight and Flash Applications

AAT2846
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 startup. After writing to Address 4 to program the
desired flash channel current level, write to
Address 5 to enable a single channel or both chan-
nels according to Table 5.
Data
FL1
FL2
1
Off
Off
2
Off
On
3
On
Off
4
On
On
Table 5: Output Enable Control, Address 5.
Writing to Address 5 enables the flash channels
indefinitely. 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 set-
ting 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.
14
2846.2007.08.1.0