A8731 Datasheet, PDF (1/16 Pages) Allegro MicroSystems – The Allegro A8731 Xenon photoflash charger IC is designed to meet the needs of ultra-low power, small form factor cameras, particularly camera-phones.

A8731
Mobile Phone Xenon Photoflash Capacitor Charger
With IGBT Driver
Features and Benefits
▪ Low quiescent current draw (0.01 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 internal gate resistors
▪ Flexible dual trigger inputs for IGBT driver
▪ Optimized for mobile phone, 1-cell Li+ battery applications
▪ No primary-side Schottky diode needed
▪ Zero-voltage switching for lower loss
▪ >75% efficiency
▪ Charge complete indication
▪ Integrated 40 V DMOS switch
Applications
▪ Mobile phone flash
▪ Digital and film camera flash
Description
The Allegro^® A8731 Xenon photoflash charger IC is designed
to meet the needs of ultra-low power, small form factor cameras,
particularly camera-phones.
The charge 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 A8731 features very low supply current
draw—typically 0.01 μA in shutdown mode and 10 μA in
standby mode.
TheA8731 has a flash dual trigger IGBTdriver.The IGBTdriver
also has internal gate resistors for minimum external component
count. The charge and trigger voltage logic thresholds are set
at 1.1 V_HI (min) to support applications implementing low
voltage control logic.
The A8731 is available in a 10-contact 3 mm × 3 mm DFN
package with a 0.75 nominal overall package height, and an
exposed pad for enhanced thermal performance.
Package: 10-contact DFN with exposed
thermal pad (package EJ)
Approximate Scale 1:1
Typical Applications
C2
ISET
RSET
CHARGE
TRIGGER1
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
VPULLUP
DONE
V_IN
IGBT Driver
100 kΩ
DONE
IGBT Gate
GATE
GND
Figure 1. Typical application with separate trigger inputs.
A8731-DS, Rev. 1
C2
ISET
RSET
CHARGE
TRIGGER1
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
VPULLUP
DONE
V_IN
IGBT Driver
100 kΩ
DONE
IGBT Gate
GATE
GND
Figure 2. Typical application with single trigger input.