AAT3151
High Efficiency 1X/1.5X/2X Charge Pump
For White LED Applications
2
al interface (>1MHz data rate), the LED current drive
AS Cwire Serial Interface
can be changed successively to brighten or dim
LEDs in smooth transitions (e.g., to fade out) or in
abrupt steps, giving the user complete programma-
bility and real-time control of LED brightness.
2
The AS Cwire single wire interface is used to set
the possible combinations of current levels and
2
LED channel states. AS Cwire has addressing
capability for multiple data registers. With multiple
data registers, the AAT3151 main and sub-chan-
nels can be programmed together or independent-
ly from one another.
For each Max Current scale, there are 16 current
level settings separated from one another by
approximately 1dB. Code 1 is full-scale current and
Code 15 is full-scale current attenuated by roughly
14dB. Code 16 is reserved as a "no current" setting
(see Table 1).
2
AS Cwire relies on the number of rising edges of
the EN/SET pin to address and load the registers.
2
AS Cwire latches data or address after the EN/SET
pin has been held high for time TLAT. Address or
data is differentiated by the number of EN/SET ris-
ing edges. Since the data registers are 4 bits each,
The AAT3151 has an additional Low Current mode
with reduced quiescent current. This mode is espe-
cially useful for low-current applications where a
continuous, low-current state is maintained. The
reduction in quiescent current significantly reduces
the impact due to maintaining a continuous back-
lighting state.
4
the differentiating number of pulses is 2 or 16, so
that Address 1 is signified by 17 rising edges,
Address 2 by 18 rising edges, and so forth. Data is
set to any number of rising edges between 1 and
including 16. A typical write protocol is a burst of
EN/SET rising edges, signifying a particular
address, followed by a pause with EN/SET held
high for the TLAT timeout period, a burst of rising
edges signifying data, and a TLAT timeout for the
data registers. Once an address is set, then multi-
ple writes to the corresponding data register are
allowed.
1
20mA Max 30mA Max 15mA Max
Data
IOUT (mA)
IOUT (mA)
IOUT (mA)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
20.0
17.8
15.9
14.3
12.7
11.1
10.2
8.9
7.9
7.0
6.3
5.7
30.0
26.7
23.8
21.4
19.0
16.7
15.2
13.3
11.9
10.5
9.5
15.0
13.3
11.9
10.7
9.5
8.3
7.6
6.7
6.0
5.2
4.8
4.3
3.8
3.3
3.1
0.0
When EN/SET is held low for an amount of time
greater than TOFF, the AAT3151 enters shutdown
mode and draws less than 1µA from the supply.
Address 1 is the default address on the first rising
edge after the AAT3151 has been disabled.
Whenever shutdown mode is entered, all registers
are reset to 1.
8.6
7.6
6.7
6.2
5.1
4.4
4.1
0.0
0.0
Table 1: Constant Current Programming
2
Levels (mA) .
1. The device defaults to the 20mA Max scale. Use the Max Current Register to change the Max Scale.
2. There is an additional Low Current mode with currents down to 50µA. See the Low Current Register Settings section.
3151.2007.03.1.10
9
AAT [ ADVANCED ANALOG TECHNOLOGY, INC. ]
