AAT1235IRN-T1 AnalogicTech, AAT1235IRN-T1 Datasheet - Page 12

• Manufacturer Part Number: AAT1235IRN-T1
• Description: High Efficiency White LED Drivers for Backlight and Keypad
• Manufacturer: AnalogicTech

AS
Application Information
Channel Disable
Tie all unused channels to AGND. On start-up, these
channels will be automatically disabled.
LED Selection
Although the AAT1235 is specifically designed to drive
white LEDs, the device can also be used to drive most
types of LEDs with forward voltages ranging between
2.0V and 4.7V. Since the A1, A2, A3, and B1, B2 input
current sinks are matched with low voltage dependence,
the LED-to-LED brightness will be matched regardless of
the individual LED forward voltage (V
instances, it may be necessary to drive high-V
LEDs. The low dropout (~0.1V @ 20mA I
sinks in the AAT1235 make it capable of driving LEDs
with forward voltages as high as 4.7V from an input sup-
ply as low as 3.0V. LED outputs A1-A3 and B1-B2 can be
combined to drive high-current LEDs without complica-
tion, making the AAT1235 a perfect application for large
LCD display backlighting and keypad LED applications.
Constant Current Setting
The LED current is controlled by the R
maximum accuracy, a 1% tolerance resistor is recom-
mended. Table 6 shows the R
AAT1235 for various LED full-scale current levels.
12
SwitchReg
2
Cwire Serial Interface Timing
TM
Data Reg 1
Data Reg 2
Address
EN/SET
SET
1
High Efficiency White LED Drivers for Backlight and Keypad
resistor value for
F
) levels. In some
SET
2
resistor. For
LED
w w w . a n a l o g i c t e c h . c o m
Address
) current
T
LO
17
0
F
T
HI
type
18
T
LAT
Maximum LED current per channel versus R
shown in Figure 1.
Table 6: Maximum LED Current and R
0
0
35
30
25
20
15
10
Figure 1: LED Current vs. R
1
I
5
0
LED
10
Values (1% Resistor Tolerance).
30
25
20
15
10
(mA)
5
36
2 . . .
Data
62
n ≤ 16
1
PRODUCT DATASHEET
88
T
114
LAT
R
140
SET
AAT1235
(kΩ Ω )
n
166
R
SET
SET
192
14.7
17.4
22.6
29.4
44.2
93.1
1235.2009.09.1.2
(kΩ)
Values.
218
SET
SET
Resistor
244
value is
270