AAT3123(2003) Ver la hoja de datos (PDF) - Advanced Analogic Technologies

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AAT3123
(Rev.:2003)

High Efficiency 1X/1.5X Fractional Charge Pump for White LED Applications

Advanced Analogic Technologies 

AAT3123/4

High Efficiency 1X/1.5X Fractional Charge

Pump for White LED Applications

Applications Information

Constant Current Output Level Settings

The constant current source output amplitude for

output D1 to D6 are set via the serial interface

according to a logarithmic scale where each code

is 1dB greater than the previous code. In this man-

ner, LED brightness appears linear with each

increasing code count. Because the outputs D1 to

D6 are true independent constant current sources,

the voltage observed on any single given output

will be determined by the actual forward voltage

(VF) for the LED being driven.

Normalized Output Current Settings

1.0

0.9

0.8

0.7

0.6

0.5

0.4

0.3

0.2

0.1

0.0

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32

Code

Since the output current of the AAT3123/24 is pro-

grammable through its simple single-wire serial

interface, no PWM (pulse width modulation) or

additional control circuitry is needed to control LED

brightness. This feature greatly reduces the burden

on a microcontroller or system IC to manage LED

or display brightness, allowing the user to "set it,

and forget it." Furthermore, with its high speed seri-

al interface (1MHz data rate), the output current of

the AAT3123/24 can changed successively to

brighten or dim LEDs, in smooth transitions (e.g. to

fade-out) or in abrupt steps, giving the user com-

plete programmability and real time control of LED

brightness.

Constant Current Source Output

Programming Levels (mA):

Code

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

IOUT

(mA)

0.549

0.627

0.706

0.784

0.863

1.020

1.098

1.255

1.412

1.569

1.804

1.961

2.275

2.510

2.824

3.137

Code

17

18

19

20

21

22

23

24

25

26

27

28

29

30

31

32

IOUT

(mA)

3.529

4.000

4.471

5.020

5.647

6.353

7.059

7.922

8.941

10.039

11.216

12.627

14.118

15.843

17.804

20.000

8

3123.2003.09.1.1

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