AAT2842INJ-EE-T1 Advanced Analog Technology, Inc., AAT2842INJ-EE-T1 Datasheet - Page 13

• Manufacturer Part Number: AAT2842INJ-EE-T1
• Description: High-Current Charge Pump with S2Cwire Control and Dual LDO for Backlight and Flash
• Manufacturer: Advanced Analog Technology, Inc.

Altering the Maximum LED Current
Level from 30mA for Backlight and
150mA for Flash
The value of R
current level for the backlight section. In the typical
application, selecting R
30mA/channel LED current. From this reference
point, the maximum current level can be modified
by calculating an alternative R
This is illustrated graphically in Figure 3.
Similarly, the value of R
mum LED current level for the flash section. In the
typical application, selecting R
in 150mA/channel LED current. From this refer-
ence point, the maximum current level can be mod-
ified by calculating an alternative R
2842.2007.09.1.2
Figure 3: Maximum LED Current vs R
Table 3: Example Output Voltages and
R2 Standard 1% Values (R1 = 120K)
35
30
25
20
15
10
Corresponding Resistor Values.
5
0
Maximum Backlight LED Current vs. R
100
V
OUT
2.8
2.5
2.0
1.8
1.5
200
R
(V)
BSET
300
BSET
400
determines the maximum LED
=
30mA · 280kΩ
500
R
FSET
BSET
BSET
I
BLED(MAX)
600
(kΩ Ω )
determines the maxi-
700
= 280kΩ results in
FSET
BSET
800
R2 (Ω)
79.6K
60.4K
30.1K
= 280kΩ results
160K
130K
value:
FSET
900
1000 1100
value:
Control and Dual LDO for Backlight and Flash
BSET
BSET
High-Current Charge Pump with S
.
This is illustrated graphically in Figure 4.
Selection of set resistor values outside of the typi-
cal application must be carefully evaluated to
ensure that the application's performance require-
ments can still be met.
Brightness Control Using the BSET and
FSET Pins
An alternative method can be used for brightness
control of the flash and/or backlight sections by uti-
lizing the corresponding set resistor pin. By using a
digital I/O port or DAC output, an alternative bright-
ness control technique can be created for each
lighting section, as shown in Figure 5.
Figure 4: Maximum Flash Current vs. R
Figure 5: Brightness Control Using Either
HI/LO
V
or
DAC
180
160
140
120
100
80
60
40
20
0
100
Maximum Flash LED Current vs. R
BSET or FSET Resistor Pin.
R
200
FSET
R
300
2
=
R
400
1
150mA · 280kΩ
500
R
I
FLED(MAX)
FSET
600
(kΩ Ω )
B/FSET
700
AAT2842
800
AAT2842
900
2
Cwire™
1000 1100
FSET
FSET
13
.