A8438
Photoflash Capacitor
Charger with IGBT Driver
Package EJ:
MLP/TDFN, 3 × 3 mm
0.75 mm nominal height
FEATURES
ꢀPower with 1 Li+ or 2 Alkaline/NiMH/NiCAD batteries
ꢀAdjustable output voltage
ꢀ>75% efficiency
ꢀThree levels of switch current limit: 1.6, 1.8, 2.0 A
ꢀFast charge time
ꢀCharge complete indication
Approximate Scale 1:1
ꢀIntegrated IGBT driver with trigger
ꢀNo primary-side Schottky diode needed
ꢀLow-profile package (0.75 mm nominal height)
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.
APPLICATIONS
ꢀDigital camera flash
ꢀFilm camera flash
ꢀCell phone flash
ꢀEmergency strobe light
Two Alkaline/NiMH/NiCAD or one Li+ battery
or 1.5 to 5.5 V
V
3.0 to 5.5 V
D1
BIAS
VBATT
VOUT
T1
C1
0.1 μF
C2
4.7 μF
R1
COUT
R4
10 kΩ
R5
100 kΩ
R2
R3
VIN
ILIM
2.0 A
1.8 A (N.C.)
1.6 A
SW
FB
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.
CHARGE
A8438
DONE
TRIGGER
IGBTDRV
To IGBT Gate
GND
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.
Figure 1. Typical circuit with separate power supply to transformer
One Li+ battery
or 3.0 to 5.5 V
V
T1
D1
BATT
VOUT
C1
0.1 μF
C2
4.7 μF
R1
COUT
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.
R4
10 kΩ
R5
100 kΩ
R2
R3
VIN
ILIM
2.0 A
SW
1.8 A (N.C.)
1.6 A
FB
CHARGE
A8438
DONE
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.
TRIGGER
IGBTDRV
To IGBT Gate
GND
Figure 2. Typical circuit with single power supply
A8438-DS, Rev. 1