AAT3151B
High Efficiency 1X/1.5X Charge Pump
For White LED Applications
2
AS Cwire Serial Interface Timing
Address
Data
THI
TLAT
TLO
TLAT
EN/SET
1
2
17
1
18
1
2 . . .
n <= 16
2
Address
Data Reg 1
Data Reg 2
1
1
n
2
AS Cwire Addressing
Max Current and Low Current Registers
A number of addresses are available to control all
of the part's functionality. Use Address 1 to pro-
gram all four LED channels to any one of 16 pos-
sible settings that depend on the Max Current
scale setting. Use Address 4 to program the Max
Current register, which sets the Max Current scale.
Address 5 programs the Low Current register. The
Low Current register controls the highly efficient
Low Current mode.
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 AAT3151B operates in the
20mA Max scale (see Constant Current
Programming 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-D4 register with 17
rising edges. Program the new constant cu rrent
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 1,
4, or 5, changing the data for Address 1 will result in
the corresponding values found in the Constant
Current Programming Levels table. When the Max
Current register is programmed to 4, the part is pro-
grammed to operate in Low Current mode and the
Data for Address 1 is irrelevant. In Low Current
mode, the Low Current register takes precedence.
See Table 4 for the available current level settings.
The AAT3151B 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 exam-
ple, 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 rising 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
significantly reduced quiescent current.
EN/SET
Edges
Addressed
Register
Address
1
4
5
17
20
21
D1-D4 Current
Max Current
Low Current
Table 2: Low Current Register Settings.
10
3151B.2007.09.1.0
ANALOGICTECH [ ADVANCED ANALOGIC TECHNOLOGIES ]
