AAT3172 View Datasheet(PDF) - Advanced Analogic Technologies
Part Name
Description
MFG CO.
'AAT3172' PDF : 15 Pages View PDF
ChargePumpTM
PRODUCT DATASHEET
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 oper-
ating 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 channels 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 shutdown,
both flash channels can be enabled to a setting 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 setting to another for the last address.
The address register is not reset after each write; there-
fore, submitting 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 addi-
tional applications. Additional applications such as auxil-
iary lighting and status LEDs can be added while elimi-
nating the need for an additional power supply, which is
normally required. Since the constant voltage mode can
supply a regulated output at up to 100mA load, it is
capable of driving five LEDs at 20mA each. It is suitable
for keypad lighting, status lighting, and other applica-
tions 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 reg-
ister and programs it to voltage mode.
2.7V to 5.5V
EN/SET
C1
C2
1µF
1µF
C1+ C1- C2+ C2-
VIN
VOUT
CIN
4.7µF
AAT 3172
EN/SET
F1
F2
GND
COUT
2.2µF
Flash
LED
AUX _EN
Figure 1: Flash Plus Auxiliary Lighting.
3172.2008.04.1.6
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