AAT1235 Analogic Corporation, AAT1235 Datasheet - Page 14

• Manufacturer Part Number: AAT1235
• Manufacturer: Analogic Corporation

If four LEDs are connected in series on one chan-
nel, the total V
as 18.8V. Therefore, using R3 = 12.1kΩ and setting
V
a 1% resistor, this results in R2 = 187kΩ (rounded to
the nearest standard 1% value).
Enable/Set
14
OUT(PROTECTION)
JP6
Number of WLEDs
3
2
1
on Each Channel
VIN
4
3
2
F
Figure 3: A AAT1235-based High Efficiency White LED Driver Schematic.
from the WLEDs could be as high
= 20V is recommended. Selecting
C1
2.2µF
R2
187k
R3
12.1k
Table 7: Over-Voltage Protection Settings.
JP1
0
R1
22.6k
JP6
0
Total Maximum V
LED1
LED2
LED3
LED4
JP2
0
JP7
0
18.8
14.1
LED6
LED7
LED8
LED9
9.4
L1: 2.2uH Taiyo Yuden NR4018T2R2M
C1: 0805 10V 2.2µF X7R GRM21BR71A225KA01
C2: 0805 25V 2.2µF X7R GRM21BR71E225KA73L
LED1-24: OSRAM LW M673 or equivalent
1
2
3
4
5
6
7
8
U1
AAT1235 TDFN3X4
VIN
OV
EN/SET
B1
B2
RSET
IN
GND
F
(V)
VOUT
AGND
MBR0530T1
SW
LIN
NC
NC
High Efficiency White LED Drivers
A1
A2
A3
It is always recommended to use the same number
of WLEDs on each channel and set the appropriate
over-voltage protection. Failure to do so may cause
any one of the (5) sink pins to exceed the absolute
maximum rating voltage and permanently damage
the device in case the channel is disconnected
(open circuit failure). Examples of over voltage set-
tings for various strings of series-connected LEDs
are shown in Table 7.
SW_Node
16
15
14
13
12
11
10
9
2.2µH
D1
L1
V
OUT(PROTECTION)
for Backlight and Keypad
20
15
10
RTN
JP3
0
JP8
0
LED11
LED12
LED13
LED14
(V)
JP4
0
JP9
0
LED16
LED17
LED18
LED19
R3 = 12.1kΩ Ω
R2 (kΩ Ω )
JP5
0
JP10
0
LED21
LED22
LED23
LED24
1235.2007.01.1.0
88.7
187
140
C2
2.2µF
25V