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PDF AAT3172 Data sheet ( Hoja de datos )
| Número de pieza | AAT3172 | |
| Descripción | High Current LED Flash Driver Charge Pump IC | |
| Fabricantes | ANALOGICTECH | |
| Logotipo |  |
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AAT3172
High Current LED Flash Driver Charge Pump IC
General Description
The AAT3172 is a high output current, high effi-
ciency, low noise, low profile charge pump DC/DC
converter, ideal for multi-function LED photo-flash
applications where solution cost, size, and efficien-
cy are critical.
The dual charge pump in the AAT3172 is capable
of delivering 600mA peak output current. Two cur-
rent-controlled paths are available for users of dual
flash LEDs that prefer current matching. Each LED
channel can be easily programmed in 32 steps with
a single GPIO output through the AS2Cwire™
(Advanced Simple Serial Control™) interface. This
allows smooth transitions and flexible adjustment
of brightness in flash or other lighting modes.
The tri-mode (1X/1.5X/2X) operation of the internal
charge pump offers excellent power efficiency for
both flash and movie modes. Combined with a low
external parts count (two 1µF flying capacitors and
one small bypass capacitor at VIN and OUT), the
AAT3172 is ideally suited for small, battery-powered
applications.
The AAT3172 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
prevents excessive inrush current during start-up.
The shutdown feature disconnects the load from VIN
and reduces quiescent current to less than 1.0µA.
The AAT3172 is available in the Pb-free, thermally-
enhanced, 12-pin 3x3 TDFN package.
Features
ChargePump™
• VIN Range: 2.7V to 5.5V
• 600mA Peak Output Current
• Tri-Mode 1X/1.5X/2X in Current Mode
• Voltage Mode Operation: 1.5X, 100mA
• Dual Regulated Current Sinks
• Current Match Between Current Sinks
• 32 Current Steps Set by AS2Cwire
• 1µF Input, Output, and Flying Capacitors
• <1.0µA of Shutdown
• Small Application Circuit
• No Inductors
• Automatic Soft Start
• 12-Pin TDFN 3x3 Package
• -40°C to +85°C Temperature Range
Applications
• Camera Phones
• Digital Still Cameras (DSCs)
• PDAs and Notebook PCs
• Smart Phones
Typical Application
2.7V to 5.5V
EN/SET
C1 C2
1µF 1µF
C1+ C1- C2+ C2-
VIN VOUT
CIN
4.7µF
AAT3172
COUT
2.2µF
Flash
LED 1
Flash
LED 2
EN/SET
GND
F1
F2
3172.2005.11.1.1
1
1 page  
AAT3172
High Current LED Flash Driver Charge Pump IC
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
50mA/ch
80 VF = 2.8V
70
152mA/ch
60 VF = 3.0V
50 95mA/ch
VF = 2.9V
40
30
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; 50mA/ch Load)
200µs/div
EN
(2V/div)
VOUT
(2V/div)
VSINK
(1V/div)
IIN
(200mA/div)
Turn-On to 1.5X Mode
(VIN = 3.2V; 50mA/ch Load)
200µs/div
EN
(2V/div)
VOUT
(2V/div)
VSINK
(1V/div)
IIN
(500mA/div)
Turn-On to 1X Mode
(VIN = 4.2V; 300mA/ch Load)
500µs/div
EN
(2V/div)
VOUT
(2V/div)
VSINK
(1V/div)
IIN
(500mA/div)
Turn-On to 2X Mode
(VIN = 3.2V; 300mA/ch Load)
500µs/div
EN
(2V/div)
VF
(1V/div)
IIN
(200mA/div)
Turn-Off from 1.5X Mode
(VIN = 3.2V; 50mA/ch Load)
200µs/div
3172.2005.11.1.1
5
5 Page 
AAT3172
High Current LED Flash Driver Charge Pump IC
Applications Information
AS2Cwire Programming
Generally, programming the AAT3172 is achieved
by submitting bursts of address and data edges to
the EN/SET pin. However, in some cases multiple
bursts of address and data are needed to enable a
particular operating mode. In other cases, only a
single burst of data edges is required.
To enable both flash channels to a current setting
on the LO scale, the user submits a single burst of
address and data edges. To enable both flash chan-
nels to a current setting on the HI scale, the user
must submit a burst of address and data edges to
program the current setting level, and then submit a
second burst of address and data edges to program
the HI/LO scale register to the HI scale.
Shortcuts can also be used. If the device is in shut-
down, both flash channels can be enabled to a set-
ting on the LO scale by just giving a single burst of
data edges. The address edges are not needed
because all registers are reset during shutdown
and address 0 is the default. Further, a single burst
of data edges can be used to change from one set-
ting to another for the last address. The address
register is not reset after each write; therefore, sub-
mitting address edges is only required when
changing the address.
Additional Applications
The constant voltage mode feature of the AAT3172
allows the user to combine the flash feature with
additional applications. Additional applications
such as auxiliary lighting and status LEDs can be
added while eliminating the need for an additional
power supply, which is normally required. Since the
constant voltage mode can supply a regulated out-
put at up to 100mA load, it is capable of driving five
LEDs at 20mA each. It is suitable for keypad light-
ing, status lighting, and other applications where a
4.5V power supply could be used.
When enabling constant voltage mode, the LED
channels F1 and F2 are automatically disabled so
current does not flow through the flash LED during
constant voltage mode. Because of this, very little
programming is required. The user just addresses
the voltage mode register and programs it to volt-
age mode.
2.7V to 5.5V
EN/SET
C1 C2
1µF 1µF
C1+ C1- C2+ C2-
VIN VOUT
CIN
4.7µF
AAT 3172
EN/SET
GND
F1
F2
COUT
2.2µF
Flash
LED
AUX _EN
Figure 1: Flash Plus Auxiliary Lighting.
3172.2005.11.1.1
11
11 Page | ||
| Páginas | Total 14 Páginas | |
| PDF Descargar | [ Datasheet AAT3172.PDF ] | |
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