A8739 Datasheet, PDF (1/21 Pages) Allegro MicroSystems – The Allegro A8739 is a Xenon photoflash charger IC designed to provide an ultra-small solution with flexibility to adjust both charging current limit and output voltage target.

A8739
Ultra-Small Mobile Adjustable Xenon Photoflash
Capacitor Charger with IGBT Driver
Features and Benefits
▪ Primary-side output voltage sensing; no resistor divider required
▪ Adjustable switch peak current limit up to 1.5 A with
single-wire programming through the CHARGE pin
▪ Option to fine-tune target voltage
▪ Ultra-small 2 × 2 DFN/MLP-8 package
▪ Integrated IGBT driver with internal gate resistors
▪ Low quiescent current draw (0.5 μA max. in shutdown mode)
▪ 1V logic (V_HI(min)) compatibility
▪ Zero-voltage switching for lower loss
▪ >75% efficiency
▪ Charge complete indication
▪ Integrated 50 V DMOS switch
Package: 8-pin DFN/MLP (suffix EE)
Not to scale
2 mm × 2 mm, 0.60 mm height
Description
The Allegro^® A8739 is a Xenon photoflash charger IC designed
to provide an ultra-small solution with flexibility to adjust
both charging current limit and output voltage target. 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. Target output voltage is primarily determined
by the transformer turns ratio, but it can be further adjusted (in
steps of –5 V each) using an external resistor. This enables better
output accuracy, as well as greater flexibility in the selection of
transformers.
To extend battery life, the A8739 features very low supply
current draw (0.5 μA max in shutdown mode and 10 μA in
standby mode). The switch current limit can be programmed
from 0.45 to 1.5 A in 16 steps with single wire interface,
through the CHARGE pin.
The IGBT driver also has internal gate resistors for minimum
external component count. The charge and trigger voltage
logic thresholds are set at 1 V_HI(min) to support applications
implementing low-voltage control logic.
The A8739 is available in an 8-contact 2 mm × 2 mm
DFN/MLP package with a 0.60 maximum overall package
height, and an exposed pad for enhanced thermal performance.
It is lead (Pb) free with 100% matte tin leadframe plating.
VIN_VDRV
C2
CHARGE
TRIG
Battery Input
2.3 to 5.5 V
+
R_BAT
C1
VBAT
VOUT Detect
SW
Control
Block
I_SW sense
Typical Applications
COUT
100F
315 V
VPULLUP
VIN_VDRV
2.3 to 5.5 V
C2
DONE
100 kΩ
CHARGE
DONE
V_{IN_VDRV}
IGBT Driver
IGBT Gate
GATE
TRIG
Battery Input
2.0 to 5.5 V
+
R_BAT
C1
VBAT
VOUT Detect
SW
Control
Block
I_SW sense
COUT
100F
315 V
VPULLUP
DONE
100 kΩ
DONE
V_{IN_VDRV}
IGBT Driver
IGBT Gate
GATE
GND
GND
(A)
(B)
Figure 1. Typical applications: (A) with single battery supply and (B) with separate bias supply
8739-DS