A8439-DS, Rev. 1
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 charg-
ing until the CHARGE pin is toggled again. 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 dif-
ferent levels between 270 mA to 1.4 A, by clocking
the CHARGE pin. This allows the user to operate the
flash even at low battery voltages.
The A8439 can be used with two Alkaline/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.
Photoflash Capacitor Charger
with IGBT Driver and Refresh
A8439
Package EJ:
MLP/TDFN, 3 × 3 mm
0.75 mm Nominal Height
FEATURES
APPLICATIONS
null Power with 1 Li+ or 2 Alkaline/NiMH/NiCAD batteries
null Adjustable output voltage
null Autorefresh
null >75% efficiency
null Eight-level, digitally-programmable current limit
null Charge complete indication
null Integrated IGBT driver with trigger
null No primary-side Schottky diode needed
null Low-profile package (0.75 mm nominal height)
null Digital camera flash
null Film camera flash
null Cell phone flash
null Emergency strobe light
Approximate Scale 1:1
Figure 1. Typical circuit with separate power supply to transformer
Figure 2. Typical circuit with single power supply
To IGBT Gate
COUT
V
OUT
D1T1
R1
R2
R3
One Li+ battery
or 3.0 to 5.5 V
V
BATT
C2
4.7 µF
C3
C1
0.1 µF
100 kΩ
R4
A8439
CHARGE
GND
FB
SW
TRIGGER IGBTDRV
DONE
VIN
+
To IGBT Gate
COUT
V
OUT
D1
T1
R1
R2
R3
100 kΩ
R4
V
BATT
Two Alkaline/NiMH/NiCAD or one Li+ battery
or 1.5 to 5.5 V
V
BIAS
3.0to5.5V
C2
4.7 µF
C1
0.1 µF
A8439
CHARGE
GND
FB
SW
TRIGGER IGBTDRV
DONE
VIN
C3