A8438-DS, Rev. 1
The A8438 is a highly integrated IC that charges
photoflash capacitors for digital and film cameras. It
also features an integrated IGBT driver that facilitates
the flash discharge function and saves board space.
To charge the photoflash capacitor, the A8438
integrates a 40 V, DMOS switch that drives the trans-
former in a flyback topology, allowing optimized
design with tight coupling and high efficiency. A pro-
prietary control scheme optimizes the capacitor charg-
ing time. Low quiescent current and low shutdown
current further improve system efficiency and extend
battery life.
Three levels of switch current limit are provided:
1.6, 1.8, and 2.0 A. The level is determined by config-
uring the ILIM pin as grounded, floating, or pulled up
to IC supply voltage, respectively.
The CHARGE pin enables the A8438 and starts the
charging of the output capacitor. When the designated
output voltage is reached, the A8438 stops the charg-
ing until the CHARGE pin is toggled again. Pulling
the CHARGE pin low stops charging. The ¯D¯ ¯O¯ ¯N¯ ¯E¯ pin
is an open-drain indicator of when the designated out-
put voltage is reached.
The A8438 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 A8438 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
A8438
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 >75% efficiency
null Three levels of switch current limit: 1.6, 1.8, 2.0 A
null Fast charge time
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
kΩ
COUT
V
OUT
D1T1
R1
R2
R3
R4
100 kΩ
R5
10
One Li+ battery
or 3.0 to 5.5 V
V
BATT
C2
4.7 µF
C1
0.1 µF
2.0 A
1.8 A (N.C.)
1.6 A
A8438
CHARGE
GND
FB
SW
TRIGGER IGBTDRV
DONE
ILIM
VIN
2.0 A
1.8 A (N.C.)
1.6 A
+
To IGBT Gate
kΩ
COUT
V
OUT
D1
T1
R1
R2
R3
R4
100 kΩ
R5
10
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
A8438
CHARGE
GND
FB
SW
TRIGGER IGBTDRV
DONE
ILIM
VIN