AAT1274

1.5A Single Flash LED Driver IC

DATA SHEET

12

Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com

201981A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • May 21, 2012

* Denotes the default value.

Address 0 controls precise movie mode current levels.

The movie mode current can be adjusted in a logarithmic

fashion to one of 16 steps represented as a fraction of

the maximum movie mode current in Table 2. On initial

EN, the movie-mode output immediately supplies 100%

of the set movie-mode current.

Data

Percentage of Maximum MM Current

1*

100%

2

89%

3

79%

4

71%

5

63%

6

56%

7

50%

8

45%

9

40%

10

36%

11

32%

12

28%

13

25%

14

22%

15

20%

16

0%

Table 2: Address 0, Movie Mode (MM)

Current Programming.

Flash to Maximum Movie Mode

Current Ratio – Address 3

The maximum movie mode current is a fixed ratio of the

flash current controlled by Address 3. The ratio may be

varied from 1:2 to OFF in 16 linear steps as shown in

Table 3. The default value for Address 3 is Data = 4 and

represents a flash to maximum movie mode current level

of 1 to 7.3. The default maximum movie mode current

can be calculated:

I

FL(MAX)

7.3

I

the flash current is set to 1500mA. For movie mode

operation, the maximum current available is then:

1500mA

7.3

I

= 206mA

The maximum movie mode current level can be calcu-

lated using the following equation:

107k

Ω × A

R

SET

1

FL to MM Ratio

I

=

= Max Movie Mode Current

Data

Flash to Movie Mode Ratio

1½

2

1/3.8

3

1/5.5

4*

1/7.3

5

1/8.9

6

1/10.5

7

1/12.2

8

1/13.8

9

1/14.9

10

1/16.5

11

1/18

12

1/19.6

13

1/21.1

14

1/22.6

15

1/24

16

OFF

Table 3: Address 3, Flash/

Movie Mode Current Ratio.

Shutdown

Since the flash current sink is the only power returns for

the flash LED loads, there is no leakage current to load

if all the sink switches are disabled. When the EN/SET

(500μs), the AAT1274 flash boost converter section

enters shutdown mode and draws less than 1μA from the

input power source. All data and address registers for

the flash and/or movie mode are cleared (reset to 0)

during shutdown.

Selecting the Boost Inductor

The AAT1274 controller utilizes PWM control and the

switching frequency is fixed. To maintain 2MHz maximum

switching frequency and stable operation, a 1μH inductor

is recommended. Manufacturer’s specifications list both

the inductor DC current rating, which is a thermal limita-

tion, and peak inductor current rating, which is deter-

mined by the saturation characteristics. Measurements at

full load and high ambient temperature should be per-

formed to ensure that the inductor does not saturate or

exhibit excessive temperature rise.