AAT3151
High Efficiency 1X/1.5X/2X Charge Pump
For White LED Applications
AS2Cwire Serial Interface
(>1MHz data rate), the LED current drive 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 programmability and
real-time control of LED brightness.
The Advanced Simple Serial Control (AS2Cwire)
single wire interface is used to set the possible
combinations of current levels and LED channel
states. AS2Cwire has addressing capability for mul-
tiple data registers. With multiple data registers, the
AAT3151 main and sub-channels can be pro-
grammed together or independently 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.
AS2Cwire relies on the number of rising edges of
the EN/SET pin to address and load the registers.
AS2Cwire 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 differentiating number of pulses is 24 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.
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.
Constant Current Programming Levels (mA)1
20mA Max 2 30mA Max 15mA Max
Data
IOUT (mA)
IOUT (mA)
IOUT (mA)
1
2
20.0
17.8
15.9
14.3
12.7
11.1
10.2
8.9
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
3
4
5
When EN/SET is held low for an amount of time
greater than TOFF, the AAT3151 enters into shut-
down mode and draws less than 1µA from the sup-
ply. Address 1 is the default address on the first ris-
ing edge after the AAT3151 has been disabled.
Whenever shutdown mode is entered, all registers
are reset to 1.
6
7
8
9
7.9
10
11
12
13
14
15
16
7.0
6.3
5.7
8.6
5.1
7.6
4.4
6.7
4.1
6.2
0.0
0.0
1. There is an additional Low Current mode with currents down to 50µA. See the Low Current Register Settings section.
2. The device defaults to the 20mA Max scale. Use the Max Current Register to change the Max Scale.
3151.2004.10.0.6
7
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