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PDF AAT3171 Data sheet ( Hoja de datos )
| Número de pieza | AAT3171 | |
| Descripción | High Efficiency Charge Pump | |
| Fabricantes | AAT | |
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AAT3171
High Current, High Efficiency
Charge Pump with Auto-Timer
General Description
Features
ChargePump™
The AAT3171 is a high output current, high effi-
ciency, low noise, low profile charge pump DC/DC
converter. The device is ideal for multi-functional
LED photo-flash applications where solution cost,
size, and efficiency are critical.
The AAT3171 is capable of driving a regulated out-
put current up to 800mA. Output current levels can
be easily programmed in 16 steps through
AnalogicTech's Simple Serial Control™ (S2Cwire™)
interface controlled by a single microcontroller
GPIO line. This allows smooth transitions and flexi-
ble adjustment of brightness in flash or other light-
ing modes. The maximum output current can also
be set with an external RSET resistor.
• Up to 800mA Output Current
• Tri-Mode 1X/1.5X/2X in Current Mode
• 16 Current Level Steps Set by S2Cwire
• External RSET to Set Maximum Current
• <1µA of Shutdown
• Small Application Circuit
• No Inductors
• Automatic Soft Start
• 12-Pin TDFN 3x3mm Package
• -40°C to +85°C Temperature Range
Applications
The tri-mode (1X/1.5X/2X) operation of the internal
•
charge pump offers excellent power efficiency
•
throughout the output current range for both flash
•
and movie modes. Combined with a low external
•
parts count (two 1µF flying capacitors and two small
•
bypass capacitors at VIN and OUT), the AAT3171 is
ideally suited for small battery-powered applications.
www.DataSheet4U.com
Camcorders
Camera Phones
Digital Still Cameras
PDAs and Notebook PCs
Smart Phones
The AAT3171 has a thermal management system to
protect the device in the event of a short-circuit con-
dition at the output pin. Built-in soft-start circuitry pre-
vents excessive inrush current during start-up. The
shutdown feature disconnects the load from VIN and
reduces quiescent current to less than 1µA.
The AAT3171 is available in a Pb-free, thermally-
enhanced 12-pin 3x3mm TDFN package and is spec-
ified over the -40°C to +85°C temperature range.
Typical Application
1µF 1µF
2.7V
to 5.5V
C1+
VIN
CIN
4.7µF
C1- C2+
AAT3171
C2+
OUT
COUT
2.2µF
Flash
LED
EN
0.1µF
EN/SET
CT
GND
FL
RSET
187K
3171.2007.03.1.1
1
1 page  
AAT3171
High Current, High Efficiency
Charge Pump with Auto-Timer
Typical Characteristics
VIN = 3.6V, CIN = 4.7µF, COUT = 2.2µF, C1 = C2 = 1µF, TA = 25°C, unless otherwise noted.
Efficiency vs. Supply Voltage
100
90
80
70
60 ILED = 300mA
50 ILED = 150mA
40
30
20
10
0
2.7 2.8 2.9 3.0 3.1 3.2 3.3 3.4 3.5 3.6 3.7 3.8 3.9 4.0 4.1 4.2
Supply Voltage (V)
EN
(2V/div)
VOUT
(2V/div)
VSINK
(1V/div)
IIN
(200mA/div)
Turn-On to 1X Mode
(VIN = 4.2V; ILED = 150mA)
Time (200µs/div)
EN
(2V/div)
VOUT
(2V/div)
VSINK
(1V/div)
IIN
(200mA/div)
Turn-On to 1.5X Mode
(VIN = 3.2V; ILED = 150mA)
Time (200µs/div)
EN
(2V/div)
VOUT
(2V/div)
VSINK
(1V/div)
IIN
(500mA/div)
Turn-On to 1X Mode
(VIN = 4.2V; ILED = 600mA)
Time (200µs/div)
EN
(2V/div)
VOUT
(2V/div)
VSINK
(1V/div)
IIN
(500mA/div)
Turn-On to 2X Mode
(VIN = 3.2V; ILED = 600mA)
Time (200µs/div)
EN
(2V/div)
VF
(1V/div)
IIN
(200mA/div)
Turn-Off from 1.5X Mode
(VIN = 3.2V; ILED = 150mA)
Time (200µs/div)
3171.2007.03.1.1
5
5 Page 
AAT3171
High Current, High Efficiency
Charge Pump with Auto-Timer
EN
ENFL
Mode
0 0 Off
0 1 Off
1 0 Flash
1 1 Torch
Table 2: Flash/Torch Control Modes.
According to I/O port type, the following equations
can be used to calculate appropriate resistor values.
For an open-drain NMOS I/O port output configu-
ration, the line is pulled low to GND or left floating,
according to state. To calculate the appropriate R1
and R2 resistor values, first calculate the R1 resis-
tor value needed for the desired torch level LED
current:
600mA · 187kΩ
R1 = ILED (torch)
Next, choose R2 based on the desired flash level
LED current:
R2
=
R1
·
R1 · 600mA · 187kΩ
ILED (flash) - 600mA · 187kΩ
The current and resistance values used in the equa-
tions come from the conditions placed on the IDX
parameter of the Electrical Characteristics table.
2.7V
to 5.5V
C1 C2
1µF 1µF
C1+
CIN
4.7µF
C1- C2+
C2+
VOUT
AAT3171
EN
ENCT
CT
EN/SET
CT
GND
F1
RSET
COUT
2.2µF
Flash
LED
R2
R1
ENFL
Figure 3: Flash/Torch Control Using the RSET Pin.
3171.2007.03.1.1
11
11 Page | ||
| Páginas | Total 19 Páginas | |
| PDF Descargar | [ Datasheet AAT3171.PDF ] | |
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