AAT3175 Datasheet, PDF (9/12 Pages) Advanced Analogic Technologies – High Efficiency 1X/1.5X/2X Charge Pump For White LED Flash Applications

AAT3175
High Efficiency 1X/1.5X/2X Charge Pump
For White LED Flash Applications
on a microcontroller or system IC to manage LED or
display brightness, allowing the user to "set it and
forget it." With its high-speed serial interface (1MHz
data rate), the input sink current of the AAT3175 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.
S²Cwire Serial Interface
The current level magnitude is controlled by
AnalogicTech's S²Cwire serial interface. The inter-
face records rising edges of the EN/SET pin and
decodes them into 16 different states. The 16 cur-
rent level settings available are indicated in Table 1.
Data
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
D2, D3
I_OUT (mA)
50
44
40
36
32
28
25
22
20
17
16
14
13
11
10
0
D1, D4
I_OUT (mA)
100
88
80
72
64
56
50
44
40
34
32
28
26
22
20
0
Table 1: Current Level Settings.
The S²Cwire serial interface has flexible timing.
Data can be clocked-in at speeds greater than
1MHz, or much slower, such as 15kHz. After data
is submitted, EN/SET is held high to latch the data.
Once EN/SET has been held in the logic high state
for time T_LAT, the programmed current becomes
active and the internal data register is reset to zero.
For subsequent current level programming, the
number of rising edges corresponding to the
desired code must be entered on the EN/SET pin.
When EN/SET is held low for an amount of time
greater than T_OFF, the AAT3175 enters into shutdown
mode and draws less than 1µA from V_IN. The internal
data register is reset to zero during shutdown.
Auto-Disable Feature
The AAT3175 is equipped with an auto-disable fea-
ture for each LED channel. After the IC is enabled
and started up, a test current of 150µA (typical) is
forced through each sink channel. The channel will
be disabled if the voltage of that particular DX pin
does not fall below a certain threshold. This feature
is very convenient for disabling an unused channel
or during an LED fail-short event.
Thermal Protection
The AAT3175 has a built-in thermal protection circuit
that will shut down the charge pump if the die tem-
perature rises above the thermal limit, as is general-
ly the case during a short-circuit of the V_OUT pin.
S²Cwire Serial Interface Timing
EN/SET
Data Reg
T_HI
T_LO
T _LAT
1
2
n-1
n ≤ 16
0
TOFF
n-1
0
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