A8439 Datasheet, PDF (1/14 Pages) Allegro MicroSystems – Photoflash Capacitor Charger with IGBT Driver and Refresh

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
V_BIAS 3.0 to 5.5 V
Two Alkaline/NiMH/NiCAD or one Li+ battery
or 1.5 to 5.5 V
V_BATT
T1
D1
VOUT
One Li+ battery
V_{BATT 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
C1
C2
R4
0.1 μF
4.7 μF
R1
100 k7
R2
VIN
SW
CHARGE
R5
FB
10 k7
A8439
R3
DONE
TRIGGER
IGBTDRV
R6
10 k7
GND
To IGBT Gate
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