AAT3172 datasheet(11/15 Pages) AAT

11 / 15 page

AAT3172

High Current LED Flash Driver Charge Pump IC

3172.2006.05.1.5

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

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.

Figure 1: Flash Plus Auxiliary Lighting.

AAT3172

EN/SET

VIN

C1+

C1- C2+

C2-

VOUT

2.7V to 5.5V

EN/SET

Flash

LED

GND

CIN

4.7µF

COUT

2.2µF

1µF

AUX_EN

AAT3172 Datasheet(PDF) 11 Page - Advanced Analog Technology, Inc.

AAT3172 Datasheet(HTML) 11 Page - Advanced Analog Technology, Inc.

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

Datasheet Download

Link URL