A8835 Datasheet, PDF (1/15 Pages) Allegro MicroSystems – The A8835 is a highly integrated IC that charges photoflash capacitors for digital and film cameras.

A8835
Photoflash Capacitor Charger
with Programmable Current Limit and IGBT Driver
Features and Benefits
▪ Eight-level, digitally-programmable current limits from
550 mA to 1.75 A
▪ Voltage sensing feedback before output diode for low
leakage
▪ No external pull-down resistors needed
▪ Power with 1 Li+ or 2 Alkaline/NiMH/NiCAD batteries
▪ Low quiescent current draw (1 μA max in shutdown mode)
▪ Zero-voltage switching for lower loss
▪ Adjustable output voltage
▪ Integrated IGBT driver with trigger
▪ Charge complete indication
▪ >75% efficiency
▪ Low-profile (0.75 mm high) 3 mm × 3 mm TDFN
10-contact package
Applications:
▪ Digital camera flash
▪ Film camera flash
▪ Cell phone flash
▪ Emergency strobe light
Package: 10-contact TDFN with exposed
thermal pad (suffix EJ)
Description
The A8835 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 A8835 and starts the charging
of the output capacitor. When the designated output voltage is
reached, the A8835 stops the charging until the CHARGE pin
is toggled again. 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 different levels
between 550 mA and 1.75 A, by clocking the CHARGE pin.
This allows the user to operate the flash even at low battery
voltages.
TheA8835 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 A8835 is available in a very low profile (0.75 mm)
10-contact 3 mm × 3 mm TDFN package, making it ideal
for space-constrained applications. It is lead (Pb) free, with
100% matte-tin leadframe plating and has an exposed pad for
enhanced thermal dissipation.
Approximate Scale
V_BIAS 3.0 to 5.5 V
R4
100 k7
V_BATT 1.5 to 5.5 V
N =10.2
T1
C1
0.1 μF
CIN
4.7 μF
VIN
SW
CHARGE
FB
A8835
DONE
TRIGGER
IGBTDRV
GND
To IGBT Gate
Typical Applications
D1
R1
150 k7
1%
R2
150 k7
1%
VOUT
COUT
100 μF
330 V
R3
1.20 k7
1%
V_BIAS 3.0 to 5.5 V
T1
R4
100 k7
C1
0.1 μF
CIN
4.7 μF
VIN
SW
CHARGE
FB
A8835
DONE
TRIGGER
IGBTDRV
GND
To IGBT Gate
D1
R1
150 k7

R2
150 k7

VOUT
COUT
R3
1.20 k7

Figure 1. Typical circuit with separate power supply to transformer
A8835-DS, Rev. 1
Figure 2. Typical circuit with single power supply