A8425 Datasheet, PDF (1/16 Pages) Allegro MicroSystems – High Current Photoflash Capacitor Charger

A8425
High Current Photoflash Capacitor Charger
with IGBT Driver for Two Li+ Batteries
Features and Benefits
▪ Wide battery voltage range: 1.5 to 11 V
▪ Integrated 55 V DMOS switch in very thin profile
3 mm × 3 mm, 0.75 mm nominal height package
▪ Peak current limit continuously adjustable from 1.0 to 3.2 A
▪ Output voltage sensing on primary side: no resistor divider
required
▪ >75% efficiency
▪ Fast charge time
▪ Charge Complete indication
▪ Flexible, high current IGBT drive
▪ Independent IGBT driver supply
▪ Separate sink and source pins with 6 Ω pull-up and
20 Ω pull-down
▪ Interlocked trigger pin improves noise immunity
▪ No primary-side Schottky diode needed
Package: 16-contact TQFN (suffix ES)
Description
The A8425 charges photoflash capacitors for digital cameras,
camcorders, and DSC combos. An integrated 55 V DMOS
switch drives the transformer in a flyback topology optimized
for 2-cell Li+ battery input. An integrated IGBT driver with
separate source and sink pins allows high performance red-eye
reduction implementation.
TheA8425 offers programmable peak switch current limit from
1.0 to 3.2 A, continuously adjustable using a resistor to ground.
A proprietary control scheme optimizes the capacitor charging
time. Low quiescent current and low shutdown current further
improve system efficiency and extend battery life.
The A8425 is available in 16-contact 3 mm × 3 mm TQFN
packages. This small, very thin profile (0.75 mm nominal overall
height) package is ideal for space-constrained applications. It
is lead (Pb) free, with 100% matte-tin leadframe plating.
Applications include:
▪ SLR camera flash
▪ Digital camcorder/DSC combo flash
▪ 2 Li+ input strobe
Approximate Scale 1:1
A8425-DS, Rev. 1
Typical Application
Bias Input
3.0 to 5.5V
Battery Input
1.5 to 11 V
C2
TLIM
+
VIN VBAT
VOUT Detect
C1
SW
ISET
RSET
Control
Block
ISW sense
1 : 10
COUT
100 μF
315 V
CHARGE
TRIGGER1
TRIGGER2
DONE
VDRV
IGBT Driver
GND
VPULLUP
100 kΩ
DONE
GSRC
GSNK
IGBT Gate