a8740 Allegro MicroSystems, Inc., a8740 Datasheet

a8740

Manufacturer Part Number

a8740

Description

Ultra Small Mobile Phone Xenon Photoflash Capacitor Charger With Igbt Driver

Manufacturer

Allegro MicroSystems, Inc.

Datasheet

1.A8740.pdf (17 pages)

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Features and Benefits

▪ Ultra small 2 × 2 DFN/MLP-8 package

▪ Low quiescent current draw (0.5 μA max. in shutdown mode)

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

▪ Fixed 1.5 A peak current limit

▪ 1.3 V logic (V

▪ Integrated IGBT driver with internal gate resistors

▪ Optimized for mobile phone, 1-cell Li+ battery applications

▪ Zero-voltage switching for lower loss

▪ >75% efficiency

▪ Charge complete indication

▪ Integrated 50 V DMOS switch with self-clamping protection

Package: 8-pin DFN/MLP (suffix EE)

Not to scale

8740-DS

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

VIN_VDRV

CHARGE

TRIG

2 mm × 2 mm, 0.60 mm height

(min)) compatibility

V IN_VDRV

VBAT

Battery Input

2.3 to 5.5 V

Control

IGBT Driver

Block

GND

(A)

DONE

VOUT Detect

Ultra Small Mobile Phone Xenon Photoflash

sense

DONE

GATE

IGBT Gate

COUT

100F

315 V

Typical Applications

VPULLUP

100 kΩ

Capacitor Charger with IGBT Driver

The Allegro

Description

to meet the needs of ultra low power, small form factor cameras,

particularly camera phones. 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 A8740 features very low supply current

draw (0.5 μA max in shutdown mode). The IGBT driver also

has internal gate resistors for minimum external component

count. The charge and trigger voltage logic thresholds are set

at 1.3 V

voltage control logic.

The A8740 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

CHARGE

TRIG

(min) to support applications implementing low-

A8740 is a Xenon photoflash charger IC designed

V IN_VDRV

VBAT

Battery Input

1.5 to 5.5 V

Control

IGBT Driver

Block

GND

DONE

(B)

VOUT Detect

sense

GATE

DONE

IGBT Gate

A8740

100F

COUT

315 V

VPULLUP

100 kΩ

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