a8739 Allegro MicroSystems, Inc., a8739 Datasheet

a8739

Manufacturer Part Number

a8739

Description

Ultra-small Mobile Adjustable Xenon Photoflash Capacitor Charger With Igbt Driver

Manufacturer

Allegro MicroSystems, Inc.

Datasheet

1.A8739.pdf (21 pages)

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Features and Benefits

▪ Primary-side output voltage sensing; no resistor divider required

▪ Adjustable switch peak current limit up to 1.5 A with

▪ 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

▪ 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

8739-DS

single-wire programming through the CHARGE pin

Figure 1. Typical applications: (A) with single battery supply and (B) with separate bias supply

VIN_VDRV

CHARGE

TRIG

(min)) compatibility

2 mm × 2 mm, 0.60 mm height

VBAT

V IN_VDRV

BAT

Control

IGBT Driver

Block

GND

Battery Input

2.3 to 5.5 V

(A)

Ultra-Small Mobile Adjustable Xenon Photoflash

DONE

VOUT Detect

sense

DONE

GATE

IGBT Gate

COUT

100F

315 V

Typical Applications

VPULLUP

100 kΩ

Capacitor Charger with IGBT Driver

The Allegro

Description

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.

external component count. The charge and trigger voltage

logic thresholds are set at 1 V

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.

The IGBT driver also has internal gate resistors for minimum

2.3 to 5.5 V

VIN_VDRV

CHARGE

A8739 is a Xenon photoflash charger IC designed

TRIG

VBAT

V IN_VDRV

BAT

Control

IGBT Driver

Block

(B)

GND

DONE

(min) to support applications

Battery Input

2.0 to 5.5 V

VOUT Detect

sense

A8739

GATE

DONE

IGBT Gate

COUT

100F

315 V

VPULLUP

100 kΩ

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