PRODUCT DATASHEET
AAT3123/23A/24
ChargePump
TM
High Efficiency 1X/1.5X Fractional Charge Pump for White LED Applications
complete programmability and real-time control of LED
brightness.
I
OUT
(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
Applications Information
Constant Current Output Level Settings
The constant current source output amplitude for out-
puts 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 manner, LED brightness
appears linear with each increasing code count. Because
the outputs D1 to D6 are true independent constant cur-
rent sources, the voltage observed on any single given
output will be determined by the actual forward voltage
(V
F
) for the LED being driven.
Since the output current of the AAT3123/23A/24 is pro-
grammable through its single-wire serial interface, no
PWM (pulse width modulation) or additional control cir-
cuitry is needed to control LED brightness. This feature
greatly reduces the burden on a microcontroller or sys-
tem IC to manage LED or display brightness, allowing
the user to “set it and forget it.” Furthermore, with its
high-speed serial interface (1MHz data rate), the output
current of the AAT3123/23A/24 can changed succes-
sively to brighten or dim LEDs in smooth transitions
(e.g., to fade-out) or in abrupt steps, giving the user
Code
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
Code
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
I
OUT
(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
Table 1: Constant Current Source Output
Programming Levels (mA).
Normalized Output Current Settings
1.0
0.9
Normalized I
OUT
(D1 to D6)
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
8
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3123.2008.03.1.5
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