A8436
Photoflash Capacitor Charger with IGBT Driver
Features and Benefits
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Power with 1 Li+ or 2 Alkaline/NiMH/NiCAD batteries
Adjustable output voltage
>75% efficiency
Three levels of switch current limit: 1.0, 1.2, 1.4 A
Fast charge time
Charge complete indication
Integrated IGBT driver with trigger
No primary-side Schottky diode needed
Low-profile package (0.75 mm nominal height)
Description
The A8436 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 A8436 integrates a
40 V, DMOS switch that drives the transformer in a flyback
topology, allowing optimized design with tight coupling and
high efficiency. A proprietary control scheme optimizes the
capacitor charging time. Low quiescent current and low
shutdown current further improve system efficiency and
extend battery life.
Three levels of switch current limit are provided: 1.0, 1.2,
and 1.4 A. The level is determined by configuring the ILIM
pin as grounded, floating, or pulled up to IC supply voltage,
respectively.
The CHARGE pin enables the A8436 and starts the charging
of the output capacitor. When the designated output voltage
is reached, the A8436 stops the charging until the CHARGE
pin is toggled again. Pulling the CHARGE pin low stops
charging. The DONE pin is an open-drain indicator of when
¯¯¯¯
¯ ¯ ¯¯
the designated output voltage is reached.
The A8436 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 A8436 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.
Package: 10 pin TDFN/MLP (suffix EJ)
Approximate Scale 1:1
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
D1
V
BATT
V
OUT
T1
+
C1
0.1 μF
C2
4.7 μF
One Li+ battery
V
BATT
or 3.0 to 5.5 V
T1
D1
V
OUT
R1
R2
R5
100 k
1.4 A
1.2 A (N.C.)
1.0 A
10 k
R4
COUT
R5
100 k
1.4 A
1.2 A (N.C.)
1.0 A
10 k
R4
C1
0.1 μF
C2
4.7 μF
R1
R2
COUT
VIN
ILIM
DONE
CHARGE
SW
FB
VIN
ILIM
DONE
CHARGE
SW
FB
A8436
IGBTDRV
GND
R3
A8436
IGBTDRV
GND
R3
R6
10 k
TRIGGER
R7
To IGBT Gate
R6
10 k
10 k
TRIGGER
R7
To IGBT Gate
10 k
Figure 1. Typical circuit with separate power supply to transformer
A8436-DS, Rev. 3
Figure 2. Typical circuit with single power supply
ALLEGRO [ ALLEGRO MICROSYSTEMS ]
