AAT2847IML-EE-T1 Advanced Analog Technology, Inc., AAT2847IML-EE-T1 Datasheet - Page 12

• Manufacturer Part Number: AAT2847IML-EE-T1
• Description: Four-Channel Backlight Driver with Dual LDOs
• Manufacturer: Advanced Analog Technology, Inc.

AS
Each white LED channel input on the AAT2847 (D1-D4) is
controlled by AnalogicTech’s AS
face. The AS
edges on the EN/SET pin to address and load the LED
configuration registers. AS
es after the EN/SET pin has been held logic high for lon-
ger than T
ated by the number of EN/SET rising edges. Since the
data registers are 4 bits each, the differentiating number
of pulses is 24 or 16, so that Address 0 is signified by 17
rising edges, Address 1 by 18 rising edges, Address 2 by
19 rising edges, and so on. Data is set to any number of
rising edges between, and including, 1 to 16.
A typical write protocol consist of the following: First a
burst of EN/SET rising edges that identify/target a par-
ticular address followed by EN/SET being held logic high
for the T
the address register, then another burst of rising edges
that signify data with the accompanying T
period to latch the data value in the data register. Once
an address is set, then multiple writes to the correspond-
ing data register are allowed without having to write to
the address for every value change in the data register.
When EN/SET is held low longer than T
AAT2847 enters shutdown mode operation and draws less
than 1µA from the input supply voltage. Data and address
registers are cleared (0 for the address register and 1 for
the data registers) in shutdown mode operation.
12
ChargePump
2
Cwire Serial Interface
30.0
25.0
20.0
15.0
10.0
Figure 1: LED Current Control Profile.
5.0
0.0
LAT
1
LAT
Address 0
timeout period to latch the address value in
2
2
(500µs). Addresses and data are differenti-
Cwire interface uses the number of rising
3
4
TM
5
6
7
8
2
Cwire latches data or address-
9 10 11 12 13 14 15 16 1
Code
2
Cwire serial digital inter-
OFF
(500µs), the
Address 4
LAT
w w w . a n a l o g i c t e c h . c o m
2
3
timeout
4
Four-Channel Backlight Driver with Dual LDOs
AS
Current Operation (Address 0)
Use Address 0 to program all four LED channels with the
current values in Table 2. All four white LED channels are
programmed to the same current level by writing to
Address 0 followed by any Data between, and including,
1 to 16.
Current Scale (Address 3)
The AAT2847 has three selectable current scales for the
four white LED channels: 30mA, 20mA, and 15mA. Only
one of the three current scales can be active at any given
time. By default, the 20mA current scale is active upon
start-up. To change to the 30mA or 15mA current scale,
or go back to the 20mA scale, write to Address 3 with
the appropriate Data between, and including, 1 to 3. To
enable low current mode, write Data 4 to Address 3. Low
current mode results in the four white LED channels
reverting to the current set by the low current settings
in Address 4.
Address
Table 1: AS
2
Data
Cwire Serial Interface Addressing
0
3
4
5
10
11
12
13
14
15
16
1
2
3
4
5
6
7
8
9
Table 2: Current Settings—Address 0.
EN/SET Edges
2
Cwire Serial Interface Addressing.
30mA
Scale
30.0
28.5
26.6
25.2
23.3
21.8
19.8
18.5
16.5
15.0
13.1
11.6
9.8
8.3
6.3
4.8
17
20
21
22
PRODUCT DATASHEET
AAT2847
20mA
Scale
Independent LED Control
Addressed Register
20.0
19.0
17.7
16.8
15.5
14.5
13.2
12.3
11.0
10.0
D1-D4 Current Control
8.7
7.7
6.5
5.5
4.2
3.2
Low Current Control
Current Scale
2847.2008.05.1.2
15mA
Scale
15.0
14.3
13.3
12.6
11.6
10.9
9.9
9.2
8.3
7.5
6.5
5.8
4.9
4.1
3.2
2.4