AAT2846_08 Datasheet, PDF (13/22 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
To enable independent channel control mode, write Data
8 to Address 15. To exit individual mode control, the
AAT2846 state machine can be reset by strobing ENS low
and holding ENS low longer than the AS²Cwire’s t_OFF latch
time.
Data
8
Individual Backlight Control
On
Table 7: Data Code for Independent
Backlight Control, Address 15.
With independent channel control mode enabled,
Addresses 2 and 3 are re-mapped according to Tables 8
and 9. As indicated by the possible settings listed in the
tables, any combination of backlighting channels can be
enabled and disabled.
Because Addresses 2 and 3 are re-mapped when inde-
pendent channel control mode is enabled, the functions
originally assigned to Addresses 2 and 3 are no longer
available.
It is also important to note that Address 0 is disabled
when independent channel control mode is enabled.
Additionally, Address 3 is disabled and the very low cur-
rent settings cannot be used in this mode. Other
addresses are unmodified by this mode so that the flash
features can still be operated and the 30mA backlight
scale can still be used.
The LDO enables are always independent of AS²Cwire
programming.
Flash LED Current Control
The flash LEDs are driven through current sinks FL1 and
FL2. There are two ways to drive the flash LEDs: either
through the AS²Cwire serial interface or through the flash
enable input, FEN. The AAT2846 also includes an adjust-
able safety timer to turn off the flash in the event of a
controller fault to prevent overstressing the flash LEDs.
Flash/Movie Mode Operation
The flash LED current level is set via the serial interface
according to a logarithmic scale where each code is
1.2dB lower than the previous code as a percentage of
the maximum current set by an external resistor, R_FSET
from FSET to AGND. Flash LED current is set between
14% and 100% of the maximum current for both chan-
nels through Address 4. For lower current applications
such as torch, flashlight, or movie light, write to Address
5 to enable only FL1 or only FL2. For higher LED current,
the flash channels can be connected in parallel to drive
the sum of the two channel currents into a single LED.
Data
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
BL6
Off
Off
Off
Off
Off
Off
Off
Off
On
On
On
On
On
On
On
On
BL5
Off
Off
Off
Off
On
On
On
On
Off
Off
Off
Off
On
On
On
On
BL4
Off
Off
On
On
Off
Off
On
On
Off
Off
On
On
Off
Off
On
On
BL3
Off
On
Off
On
Off
On
Off
On
Off
On
Off
On
Off
On
Off
On
Table 8: Data Code for BL3-BL6
On/Off Control, Sub-Address 2.
Data
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
BL2
Off
Off
Off
Off
Off
Off
Off
Off
On
On
On
On
On
On
On
On
BL1
Off
Off
Off
Off
On
On
On
On
Off
Off
Off
Off
On
On
On
On
Table 9: Data Code for BL1 and BL2
On/Off Control, Sub-Address 3.
2846.2008.03.1.1
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