AAT2869 Advanced Analogic Technologies, Inc., AAT2869 Datasheet - Page 15

• Manufacturer Part Number: AAT2869
• Description: Fade-in/fade-out 4 Channel Backlight Driver With Dual Ldos
• Manufacturer: Advanced Analogic Technologies, Inc.

Application Information
LED Selection
The AAT2869 is designed to drive high intensity white
flash LEDs with forward voltages up to 4.4V. Though
AAT2869 switches the charge pump mode 1x and 1.5x
mode automatically to maintain the continuous LED cur-
rent accuracy, to obtain higher efficiency lower V
LEDs should be selected.
Maximum LED Current Setting
32 maximum LED current codes from 0.4mA to 31mA can
be set by two registers using addresses 2 and 3 through
the EN/SET AS
obtain linear LED current change, the AAT2869 will not
change the LED current when only address 2 is written.
The control circuit only loads data to the address 2 and
2869.2010.01.1.0
SystemPower
2
Cwire interface as shown in Figure 2. To
Data Reg
Address
EN/SET
TM
Figure 2: AAT2869 Total 32 LED Current Codes vs. LED Current.
32
30
28
26
24
22
20
18
16
14
12
10
8
6
4
2
0
1
2
1
3
4
Fade-In/Fade-Out 4 Channel Backlight Driver with Dual LDOs
5
2
6
7
Figure 1: AS
8
Address
0
9
T
LO
19
10
w w w . a n a l o g i c t e c h . c o m
11
T
HI
F
12
white
2
13
LED Current Code
Cwire Timing Diagram.
14 15
20
T
LAT
16
17
address 3 registers after address 3 is written to determine
which LED current code is programmed. The address 2
BL4 default value is 0 after one EN/SET rising edge.
Codes 1 to 16 with LED current from 0.4mA to 15mA can
be set after sending 20 rising edges to address 3 and
sending data with 1 to 16 rising edges after t
17 to 32 with LED current from 16mA to 31mA can be
obtained after writing both address 2 and address 3. This
operation is performed using the following steps:
1. Select address 2 by sending 19 rising edges to EN/SET
2. Send data 1 to set DL4 by sending 2 rising edges and
3. Select address 3 by sending 20 rising edges on EN/
4. Send data 15 to enable LED current code 32 setting by
0
18 19
and holding high for t
holding high for t
SET and holding high for t
sending 16 rising edges on EN/SET and holding high
for t
1
LAT
20
.
21
22 23
Data
2
24
3
25
LAT
26 27 28 29
PRODUCT DATASHEET
;
LAT
n ≤ 16
;
T
LAT
LAT
30
AAT2869
;
31
32
n
LAT
. Codes
15