AAT3156
High Efficiency 1X/1.5X/2X Charge Pump
For White LED Applications
AS2Cwire Serial Interface Timing
Address
THI
Data
TLAT
TLO
TLAT
EN/SET
1
2
17
18
1
2 . . .
n <= 16
Address
Data Reg 1
Data Reg 2
1
2
1
1
n
AS2Cwire Addressing
Max Current and Low Current Registers
Five addresses are available to enable all of the
part's functionality. Two 4-bit registers control the
main and sub-channels, giving 16 settings for each.
The main and sub-channels are programmed to the
same constant current level by using Address 1.
Use Addresses 2 and 3 to program the main and
sub-channels independently. Use Address 4 to pro-
gram the Max Current register, which sets the Max
Current scale. Lastly, Address 5 programs the Low
Current register. The Low Current register controls
the efficient Low Current mode. When the Max
Current register is programmed to 1, 2, or 3, chang-
ing the data for Addresses 1-3 will result in the cor-
responding values found in the Constant Current
Programming Levels table.
Use the Max Current and Low Current registers to
program constant current settings outside of the
20mA Max scale. By default (without changing the
Max Current register), the AAT3156 operates in the
20mA Max scale (see Constant Current Program-
ming Levels). For example, to change to the 30mA
Max scale, address the Max Current register with
20 rising edges and pause for TLAT. Program the
Max Current register with 2 rising edges and pause
for TLAT. The part will next operate in the same Data
row, but for the setting found in the 30mA Max col-
umn. Next, to change to a different setting on the
30mA Max scale, address the D1-D6 register with
17 rising edges. Program the new constant current
level with 1-16 rising edges. The part will update to
the new Data setting according to the Constant
Current Programming Levels table.
When the Max Current register is programmed to 4,
the part is programmed to operate in Low Current
mode and the Data for Addresses 1-3 is irrelevant.
In Low Current mode, the Low Current register
takes precedence. See the Low Current Register
Settings table below for the current level settings
and main/sub-configurations that result.
The AAT3156 has a distinct Low Current mode with
ultra-low quiescent current. For drive currents of
2mA or less, the part operates with significantly
reduced quiescent current. This is particularly use-
ful for applications requiring an "always on" condi-
tion such as transmissive displays. As an example,
to change to Low Current mode, address the Max
Current register with 20 rising edges and pause for
TLAT. Program the Max Current register with 4 ris-
ing edges and pause for TLAT. Address the Low
Current register with 21 rising edges and pause for
TLAT. Program the Low Current register with 1-16
rising edges. The part will update to the new Low
Current mode setting and operate with significant-
ly reduced quiescent current.
EN/SET
Edges
Addressed
Register
Address
1
17
1&2: D1-D6
Current
2
3
4
5
18
19
20
21
1: D1-D4 Current
2: D5-D6 Current
3: Max Current
4: Low Current
10
3156.2005.09.1.2
ANALOGICTECH [ ADVANCED ANALOGIC TECHNOLOGIES ]
