|
|
PDF A8439 Data sheet ( Hoja de datos )
| Número de pieza | A8439 | |
| Descripción | Photoflash Capacitor Charger | |
| Fabricantes | Allegro MicroSystems | |
| Logotipo |  |
|
Hay una vista previa y un enlace de descarga de A8439 (archivo pdf) en la parte inferior de esta página. Total 14 Páginas | ||
|
No Preview Available !
www.DataSheet4U.com
A8439
Photoflash Capacitor Charger
with IGBT Driver and Refresh
Features and Benefits
▪ Power with 1 Li+ or 2 Alkaline/NiMH/NiCAD batteries
▪ Adjustable output voltage
▪ Auto-refresh
▪ >75% efficiency
▪ Eight-level, digitally-programmable current limit
▪ Charge complete indication
▪ Integrated IGBT driver with trigger
▪ No primary-side Schottky diode needed
▪ Low-profile package (0.75 mm nominal height)
Package: 10 pin TDFN/MLP (suffix EJ)
Approximate Scale
Description
The A8439 is a highly integrated IC that charges photoflash
capacitors for digital and film cameras.An integrated MOSFET
switch drives the transformer in a flyback topology. It also
features an integrated IGBT driver that facilitates the flash
discharge function and saves board space.
The CHARGE pin enables the A8439 and starts the charging
of the output capacitor. When the designated output voltage is
reached, the A8439 stops the charging until the CHARGE pin
is toggled again, or when output voltage falls below 90% of
the designated value. Pulling the CHARGE pin low stops the
charging. The D¯¯O¯¯N¯¯E¯¯ pin is an open-drain indicator of when
the designated output voltage is reached.
The peak current limit can be adjusted to eight different levels
between 270 mA and 1.4 A, by clocking the CHARGE pin.
This allows the user to operate the flash even at low battery
voltages.
TheA8439 can be used with twoAlkaline/NiMH/NiCAD or one
single-cell Li+ battery connected to the transformer primary.
Connect the VIN pin to a 3.0 to 5.5 V supply, which can be
either the system rail or the Li+ battery, if used.
The A8439 is available in a very low profile (0.75 mm) 10-
terminal 3×3 mm MLP/TDFN package, making it ideal for
space-constrained applications. It is lead (Pb) free, with 100%
matte-tin leadframe plating.
Applications include the following:
▪ Digital camera flash
▪ Film camera flash
▪ Cell phone flash
▪ Emergency strobe light
Typical Applications
VBIAS 3.0 to 5.5 V
Two Alkaline/NiMH/NiCAD or one Li+ battery
or 1.5 to 5.5 V
VBATT
T1 D1
VOUT
One Li+ battery
VBATT or 3.0 to 5.5 V
T1 D1
R4
100 k7
C1
0.1 μF
C2
4.7 μF
R5
10 k7
VIN
CHARGE
DONE
SW
FB
A8439
TRIGGER
IGBTDRV
R6
10 k7
GND
To IGBT Gate
R1 COUT
R2
R3 C3
R4
100 k7
C1
0.1 μF
C2
4.7 μF
R5
10 k7
VIN
CHARGE
DONE
SW
FB
A8439
TRIGGER
IGBTDRV
R6
10 k7
GND
To IGBT Gate
R1
R2
R3
VOUT
COUT
C3
Figure 1. Typical circuit with separate power supply to transformer
A8439-DS, Rev. 5
Figure 2. Typical circuit with single power supply
1 page  
A8439
Photoflash Capacitor Charger with IGBT Driver and Refresh
Operation Timing Diagram
VUVLO
VIN
CHARGE
SW
Target VOUT
VOUT
DONE
TRIGGER
IGBTDRV
A
B
C
DE
F
Explanation of Events:
A. Start charging by pulling CHARGE to high, provided that VIN is above the VUVLO level.
B. Charging stops when VOUT reaches the target voltage. ¯D¯¯O¯¯N¯¯E¯ goes low, to signal the
completion of the charging process.
C. Start a new charging process with a low-to-high transition at the CHARGE pin.
D. Pull CHARGE to low, to put the controller in low-power standby mode.
E. Charging does not start, because VIN is below VUVLO level when CHARGE goes high.
F. After VIN goes above VUVLO, another low-to-high transition at the CHARGE pin is
required to start charging.
Allegro MicroSystems, Inc.
5
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com
5 Page 
A8439
Photoflash Capacitor Charger with IGBT Driver and Refresh
Figure 7 shows the last charging cycle, when the CHARGE pin is
forced low before charging has been completed.
The A8439 implements an adaptive off-time, tOFF , control.
After the switch is turned off, a sensing circuit tracks the flyback
voltage at the SW node. As soon as this voltage swings below
1.2 V, the switch is turned on again for the next charging cycle.
However, when the photoflash capacitor charger circuit starts
up at low output voltage, a timeout may be triggered to limit the
maximum switch off-time to 20 μs.
Figure 7. Last charging cycle, when the CHARGE pin is forced low before
charging is complete.
Allegro MicroSystems, Inc.
11
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com
11 Page | ||
| Páginas | Total 14 Páginas | |
| PDF Descargar | [ Datasheet A8439.PDF ] | |
Hoja de datos destacado
| Número de pieza | Descripción | Fabricantes |
| A8430 | White LED Driver Constant Current Step-up Converter | Allegro MicroSystems |
| A8431 | White LED Driver Constant Current Step-up Converter | Allegro MicroSystems |
| A8434 | 6-Channel High Efficiency Charge Pump White LED Driver | Allegro MicroSystems |
| A8435 | High Efficiency Charge Pump White LED Driver | Allegro MicroSystems |
| Número de pieza | Descripción | Fabricantes |
| SLA6805M | High Voltage 3 phase Motor Driver IC. |
 Sanken |
| SDC1742 | 12- and 14-Bit Hybrid Synchro / Resolver-to-Digital Converters. |
 Analog Devices |
|
DataSheet.es es una pagina web que funciona como un repositorio de manuales o hoja de datos de muchos de los productos más populares, |
| DataSheet.es | 2020 | Privacy Policy | Contacto | Buscar |