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PDF AAT1270 Data sheet ( Hoja de datos )
| Número de pieza | AAT1270 | |
| Descripción | 1A Step-Up Current Regulator | |
| Fabricantes | AAT | |
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AAT1270
1A Step-Up Current Regulator for Flash LEDs
General Description
SwitchReg™
The AAT1270 is a high-efficiency, high-current boost
converter capable of 1A maximum output current. It
is an ideal power solution for LED photo flash appli-
cations in all single-cell Lithium-ion / polymer battery
operated products.
The AAT1270 maintains output current regulation by
switching the internal high-side and low-side switch
transistors. The transistor switches are pulse-width
modulated at a fixed frequency of 2MHz. The high
switching frequency allows the use of a small induc-
tor and output capacitor, making the AAT1270 ideal-
ly suited for small battery-powered applications.
AnalogicTech’s proprietary S2Cwire™ (Simple Serial
Control™) serial digital interface is used to enable,
disable and set the movie mode current level for the
flash LEDs to one of 16 levels. The AAT1270 also
includes a separate Flash Enable input to initiate both
flash/strobe operation and the default timer, which
can be used to terminate a flash event after a user-
programmed delay or as a safety feature. A Flash
Inhibit pin is also included which reduces flash cur-
rent to movie mode level during high battery demand.
The maximum flash and movie mode current is set
by one external resistor; the ratio between flash and
movie mode current is set at approximately 7.3:1.
One or two LEDs can be connected to the AAT1270;
when two LEDs are used, the output current is
matched between each diode.
The AAT1270 contains over-voltage protection and a
thermal management system to protect the device in
the event of an output open-circuit and short-circuit
condition respectively. Built-in circuitry prevents exces-
sive inrush current during start-up. The shutdown fea-
ture reduces quiescent current to less than 1.0µA.
Typical Application
The AAT1270 is available in a Pb-free, thermally-
enhanced 14-pin 3x3mm STDFN package.
Features
• Input Voltage Range: 2.7V to 5.5V
• Dual Channel Output
— Up to 1A Regulated Output Current
(0.5A per Channel)
• Up to 85% Efficiency with Small Magnetics
• 2 MHz Switching Frequency
• Separate Flash Enable Input
• Separate Flash Inhibit Input
• Single Resistor Sets Flash and Movie Mode Current
— Fixed Flash-to-Movie Mode Current Ratio
• 16-Level Movie Mode Current via S2Cwire™
• User-Programmable Safety Timer
• True Load Disconnect
• Input Current Limit
• Over-Voltage (Open LED, Open Circuit), Short-
Circuit, and Over-Temperature Protection
• Shutdown Current: < 1.0µA
• Small Inductor Solution: 1µH (0.9mm in height)
• 14-pin STDFN 3x3 Package
• -40 to +85°C Temperature Range
Applications
• Camcorder Video Light (Torch Light)
• Cellphones / Smartphones
• Digital Still Cameras (DSC)
• LED Photo Flash Light (Strobe Light)
• Mobile Handsets
• MP3 Players
• PDAs and Notebook PCs
L1
1μH
VBATTERY
Movie Mode
Enable and Set
Flash Enable
Flash Inhibit
CIN
2.2μF
RSET
162kΩ
IN SW
OUT
AAT1270
EN/SET
FLEN
FLINH
FLOUTA
FLOUTB
RSET
CT
GND AGND PGND FLGND
Flash LEDs
Lumiled LXCL-PWF1 or equivalent
COUT
2.2μF
CT
47nF
1270.2007.07.1.0
1
1 page  
AAT1270
1A Step-Up Current Regulator for Flash LEDs
Typical Characteristics
90
85
80
75
70
65
60
55
50
45
40
2.7
Efficiency vs. Input Voltage
(Movie and Flash Mode)
68.5mA
(Movie)
500mA
(Flash)
34.25mA
(Movie)
13.7mA
(Movie)
3.1 3.5 3.9 4.3 4.7 5.1
Input Voltage (V)
5.5
Shutdown Current vs. Input Voltage
(EN/SET = FLEN = 0V)
0.12
0.1
0.08
0.06
0.04
0.02
0
2.7 3.1 3.5 3.9 4.3 4.7 5.1 5.5
Input Voltage (V)
Switching Frequency vs. Input Voltage
(EN/SET = FLEN = 0V)
3.0
2.5 -40°C
2.0
1.5
1.0 85°C
25°C
0.5
0.0
2.7 3.1 3.5 3.9 4.3 4.7 5.1 5.5
Input Voltage (V)
Movie Mode LED Current Accuracy vs. Input Voltage
(68.5mA/Ch)
10
5 FLOUTB
0
-5 FLOUTA
-10
2.7 3.1 3.5 3.9 4.3 4.7 5.1 5.5
Input Voltage (V)
Movie Mode Current Matching vs. Temperature
(68.5mA/ch)
70.5
70.0 FLOUTA
69.5
69.0
68.5
68.0
67.5 FLOUTB
67.0
66.5
66.0
65.5
-40 -15 10 35 60 85
Temperature (°C)
Flash Mode Current Matching vs. Temperature
(500mA/ch)
515
510
505
500
FLOUTA
495
FLOUTB
490
485
-40 -15 10 35 60 85
Temperature (°C)
1270.2007.07.1.0
5
5 Page 
AAT1270
1A Step-Up Current Regulator for Flash LEDs
to which the AAT1270 movie mode operation can
be programmed.
S2Cwire
Data
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
Percentage of Maximum
Movie Mode Current (%)
100
89
79
71
63
56
50
44.7
39.8
35.5
31.6
28.2
25.1
22.4
20
0
Table 1: Programming Movie Mode
Current via S2Cwire (%).
S2Cwire Serial Interface
The Simple Serial Control (S2Cwire) serial interface
records rising edges at the EN/SET pin and decodes
them into 16 different states. The S2Cwire serial
interface has flexible timing. Data can be applied at
speeds faster than 1MHz, or at much slower speeds,
such as 15kHz. After data is applied, EN/SET is
strobed high and held high to latch the data.
Once the signal applied at the EN/SET pin has
been held in the logic high state for time longer
than tLAT (500µs), the programmed current
becomes active and the internal data register is
reset to zero. For subsequent current level pro-
gramming, the number of rising edges correspon-
ding to the desired code must be applied to the
EN/SET pin.
EN/SET
Data Reg
THI
TLO
T LAT
TOFF
12
n-1 n ≤ 16
0
n-1
Figure 1: S2Cwire Serial Interface Timing
0
1270.2007.07.1.0
11
11 Page | ||
| Páginas | Total 18 Páginas | |
| PDF Descargar | [ Datasheet AAT1270.PDF ] | |
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