AAT3123 ETC, AAT3123 Datasheet - Page 8

• Manufacturer Part Number: AAT3123
• Description: High Efficiency 1X/1.5X Fractional Charge Pump for White LED Applications
• Manufacturer: ETC

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
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.
8
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
Normalized Output Current Settings
10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32
High Efficiency 1X/1.5X Fractional Charge
Code
Pump for White LED Applications
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
Constant Current Source Output
Programming Levels (mA):
F
) for the LED being driven.
Code
10
11
12
13
14
15
16
1
2
3
4
5
6
7
8
9
(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
I
OUT
Code
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
3123.2003.09.1.1
10.039
12.627
15.843
17.804
20.000
11.216
14.118
(mA)
3.529
4.000
4.471
5.020
5.647
6.353
7.059
7.922
8.941
I
OUT