A8437 Datasheet, PDF (1/21 Pages) Allegro MicroSystems – Mobile Phone Xenon Photoflash Capacitor Charger

A8437
Mobile Phone Xenon Photoflash Capacitor Charger
with IGBT Driver
Features and Benefits
▪ Low quiescent current draw (0.1 μA in shutdown mode)
▪ Primary-side output voltage sensing; no resistor divider
required
▪ User-adjustable current limit from 0.4 to 1.2 A
▪ 1.1 V logic (V_HI(min)) compatibility
▪ Integrated IGBT driver with separate sink and source (CG
package) or common sink/source (EJ package)
▪ Flash dual trigger with interlock for increased noise
immunity
▪ Optimized for mobile phone, 1-cell Li+ battery applications
▪ No primary-side Schottky diode needed
▪ Zero-voltage switching for lower loss
▪ >75% efficiency
▪ Optional regulation feature to maintain the output voltage
▪ Charge complete indication
▪ Integrated 40 V DMOS switch
Packages:
10-contact DFN/MLP
3 mm × 3 mm
0.75 nominal overall height
(Package EJ)
12-ball WLCSP
1.205 mm × 1.635 mm
0.5 nominal overall height
(Package CG)
Description
The Allegro^® A8437 Xenon photoflash charger IC is designed
to meet the needs of ultra-low power, small form factor cameras,
particularly camera-phones.
The charge current time is adjustable by setting the charge
current limit from 0.4 to 1.2 A maximum. By using primary-
side voltage sensing, the need for a secondary-side resistive
voltage divider is eliminated. This has the additional benefit
of reducing leakage currents on the secondary side of the
transformer. To extend battery life, the A8437 features very
low supply current draw—typically 0.1 μA in shutdown mode
and 10 μA in standby mode.
The A8437 has a flash dual trigger IGBT driver and flash
interlock to increase the device noise immunity. The IGBT
driver also has separate source and sink connections, for
flexibility in controlling IGBT rise and fall times. The charge
and trigger voltage logic thresholds are set at 1.1 V_HI (min)
to support applications implementing low voltage control
logic.
The A8437 is available in a 10-pin, 3 mm × 3 mm DFN/MLP
package with exposed pad for enhanced thermal performance.
For an even smaller PCB footprint, a wafer-level chip scale
package (WLCSP) option is available.
Applications include:
▪ Mobile phone flash
▪ Digital and film camera flash
CG Package
Typical Application
EJ Package
C2
TLIM
ISET
RSET
CHARGE
Battery Input ⁺
2.3 to 5.5 V
VIN
VOUT Detect
1 : 10
C1
COUT
100 μF
315 V
SW
Control
Block
I_SW sense
Connect
to VIN
DONE
REG
VPULLUP
100 kΩ
DONE
C2
ISET
RSET
Application 1. Typical application
without output voltage regulation.
Note: Application must
periodically restart the charging
cycle to recover lost charge on
the output capacitor.
CHARGE
TRIGGER1
IGBT Driver
GSOURCE
IGBT Gate
TRIGGER1
TRIGGER2
A8437-DS, Rev. 1
GND
GSINK
TRIGGER2
Battery Input ⁺
2.3 to 5.5 V
VIN
VOUT Detect
1 : 10
C1
COUT
100 μF
315 V
SW
Control
Block
I_SW sense
Connect
to VIN
DONE
REG
VPULLUP
100 kΩ
VIN
IGBT Driver
DONE
IGBT Gate
GATE
GND