AAT3172 Datasheet, PDF (11/14 Pages) Advanced Analogic Technologies – High Current LED Flash Driver Charge Pump IC

AAT3172
High Current LED Flash Driver Charge Pump IC
Applications Information
AS²Cwire Programming
Generally, programming the AAT3172 is achieved
by submitting bursts of address and data edges to
the EN/SET pin. However, in some cases multiple
bursts of address and data are needed to enable a
particular operating mode. In other cases, only a
single burst of data edges is required.
To enable both flash channels to a current setting
on the LO scale, the user submits a single burst of
address and data edges. To enable both flash chan-
nels to a current setting on the HI scale, the user
must submit a burst of address and data edges to
program the current setting level, and then submit a
second burst of address and data edges to program
the HI/LO scale register to the HI scale.
Shortcuts can also be used. If the device is in shut-
down, both flash channels can be enabled to a set-
ting on the LO scale by just giving a single burst of
data edges. The address edges are not needed
because all registers are reset during shutdown
and address 0 is the default. Further, a single burst
of data edges can be used to change from one set-
ting to another for the last address. The address
register is not reset after each write; therefore, sub-
mitting address edges is only required when
changing the address.
Additional Applications
The constant voltage mode feature of the AAT3172
allows the user to combine the flash feature with
additional applications. Additional applications
such as auxiliary lighting and status LEDs can be
added while eliminating the need for an additional
power supply, which is normally required. Since the
constant voltage mode can supply a regulated out-
put at up to 100mA load, it is capable of driving five
LEDs at 20mA each. It is suitable for keypad light-
ing, status lighting, and other applications where a
4.5V power supply could be used.
When enabling constant voltage mode, the LED
channels F1 and F2 are automatically disabled so
current does not flow through the flash LED during
constant voltage mode. Because of this, very little
programming is required. The user just addresses
the voltage mode register and programs it to volt-
age mode.
2.7V to 5.5V
EN/SET
C1
C2
1µF
1µF
C1+ C1- C2+ C2-
VIN
VOUT
C_IN
4.7µF
AAT 3172
EN/SET
F1
F2
GND
C_OUT
2.2µF
Flash
LED
AUX _EN
Figure 1: Flash Plus Auxiliary Lighting.
3172.2005.11.1.1
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