AAT3123 Datasheet, PDF (8/18 Pages) List of Unclassifed Manufacturers – High Efficiency 1X/1.5X Fractional Charge Pump for White LED Applications

AAT3123/23A/24
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
outputs 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
(V_F) 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 AAT3123/23A/24 is
programmable through its single-wire serial inter-
face, no PWM (pulse width modulation) or addi-
tional 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
serial interface (1MHz data rate), the output current
of the AAT3123/23A/24 can changed successively
to brighten or dim LEDs in smooth transitions (e.g.,
to fade-out) or in abrupt steps, giving the user
complete programmability and real-time control of
LED brightness.
Code
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
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
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).
8
3123.2005.12.1.4