AAT3142ITP-T1 AnalogicTech, AAT3142ITP-T1 Datasheet - Page 10

• Manufacturer Part Number: AAT3142ITP-T1
• Description: High Efficiency 1X/1.5X/2X Charge Pump for White LED Applications
• Manufacturer: AnalogicTech

Applications Information
Constant Current Output Level Settings
The constant current source amplitudes for D1 to D3 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 D3 are
true independent constant current sources, the voltage
observed on any single given output will be determined by
the actual forward voltage (V
Since the output current of the AAT3142 is programma-
ble, no PWM (pulse width modulation) or additional con-
10
ChargePump
Code
1
2
3
4
5
6
7
8
I
OUT
(typ) (mA)
TM
0.0
0.1
0.2
0.4
0.5
0.7
1.1
1.8
Table 1: Constant Current Source Output Nominal Programming Levels.
1.00
0.10
0.01
0.00
High Efficiency 1X/1.5X/2X Charge Pump for White LED Applications
1
2
F
) for the LED being driven.
3
Code
4
10
11
12
13
14
15
16
Figure 1: Normalized Current Level Settings.
9
5
6
7
I
8
OUT
9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32
(typ) (mA)
w w w . a n a l o g i c t e c h . c o m
2.0
2.2
2.5
2.8
3.2
3.5
4.0
4.5
Code
trol circuitry are 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.” With its high-
speed serial interface (1MHz data rate), the output cur-
rent of the AAT3142 can be changed successively to
brighten or dim LEDs in smooth transitions (e.g., to fade
out) or in abrupt steps, giving the user complete pro-
grammability and real-time control of LED brightness.
The individual current level settings are each approxi-
mately 1dB apart for settings above Code 8 (see Figure
1). The current level settings below Code 8 are more
than 1dB apart and serve the needs of transmissive dis-
plays and other low-current applications.
17
18
19
20
21
22
23
24
I
OUT
(typ) (mA)
5.1
5.6
10
12
6
7
8
9
PRODUCT DATASHEET
Code
25
26
27
28
29
30
31
32
AAT3142
I
OUT
3142.2009.07.1.3
(typ) (mA)
13
15
17
19
21
24
27
30