A8438_13 Datasheet, PDF (1/15 Pages) Allegro MicroSystems – Photoflash Capacitor Charger with IGBT Driver

A8438
Photoflash Capacitor Charger with IGBT Driver
Features and Benefits
▪ 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
▪ 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 1:1
Description
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 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: 1.6, 1.8,
and 2.0 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 A8438 and starts the charging
of the output capacitor. When the designated output voltage
is reached, the A8438 stops the charging 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 output voltage is reached.
TheA8438 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 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.
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
C1
0.1 μF
C2
4.7 μF
R1
R5
R4
100 k7
10 k7
R2
2.0 A
1.8 A (N.C.)
VIN
ILIM
SW
1.6 A
FB
DONE
A8438
R3
CHARGE
R6
10 k7
TRIGGER
IGBTDRV
R7
10 k7
GND
To IGBT Gate
COUT
One Li+ battery
V_{BATT or 3.0 to 5.5 V}
T1
D1
VOUT
C1
0.1 μF
C2
4.7 μF
R1
R5
100 k7
R4
10 k7
R2
2.0 A
1.8 A (N.C.)
VIN
ILIM
SW
1.6 A
FB
DONE
A8438
R3
CHARGE
R6
10 k7
TRIGGER
IGBTDRV
R7
10 k7
GND
To IGBT Gate
COUT
Figure 1. Typical circuit with separate power supply to transformer
Figure 2. Typical circuit with single power supply
A8438-DS, Rev. 2