a8439eej-t Allegro MicroSystems, Inc., a8439eej-t Datasheet

a8439eej-t

Manufacturer Part Number

a8439eej-t

Description

A8439 Photoflash Capacitor Charger With Igbt Driver And Refresh

Manufacturer

Allegro MicroSystems, Inc.

Datasheet

1.A8439EEJ-T.pdf (14 pages)

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Features and Benefits

▪ Power with 1 Li+ or 2 Alkaline/NiMH/NiCAD batteries

▪ Adjustable output voltage

▪ Auto-refresh

▪ >75% efficiency

▪ Eight-level, digitally-programmable current limit

▪ Charge complete indication

▪ Integrated IGBT driver with trigger

▪ No primary-side Schottky diode needed

▪ Low-profile package (0.75 mm nominal height)

Package: 10 pin TDFN/MLP (suffix EJ)

Figure 1. Typical circuit with separate power supply to transformer

A8439-DS, Rev. 5

BIAS

100 k

3.0 to 5.5 V

Approximate Scale

10 k

CHARGE

TRIGGER

DONE

VIN

GND

0.1 μF

BATT

IGBTDRV

A8439

Two Alkaline/NiMH/NiCAD or one Li+ battery

or 1.5 to 5.5 V

4.7 μF

To IGBT Gate

Typical Applications

COUT

OUT

with IGBT Driver and Refresh

Photoflash Capacitor Charger

Description

The A8439 is a highly integrated IC that charges photoflash

capacitors for digital and film cameras. An integrated MOSFET

switch drives the transformer in a flyback topology. It also

features an integrated IGBT driver that facilitates the flash

discharge function and saves board space.

The CHARGE pin enables the A8439 and starts the charging

of the output capacitor. When the designated output voltage is

reached, the A8439 stops the charging until the CHARGE pin

is toggled again, or when output voltage falls below 90% of

the designated value. Pulling the CHARGE pin low stops the

charging. The ¯ D ¯ ¯ O ¯ ¯ N ¯ ¯ E ¯ pin is an open-drain indicator of when

the designated output voltage is reached.

The peak current limit can be adjusted to eight different levels

between 270 mA and 1.4 A, by clocking the CHARGE pin.

This allows the user to operate the flash even at low battery

voltages.

The A8439 can be used with two Alkaline/NiMH/NiCAD or one

single-cell Li+ battery connected to the transformer primary.

Connect the VIN pin to a 3.0 to 5.5 V supply, which can be

either the system rail or the Li+ battery, if used.

The A8439 is available in a very low profile (0.75 mm) 10-

terminal 3×3 mm MLP/TDFN package, making it ideal for

space-constrained applications. It is lead (Pb) free, with 100%

matte-tin leadframe plating.

Applications include the following:

Figure 2. Typical circuit with single power supply

▪ Digital camera flash

▪ Film camera flash

BATT

100 k

One Li+ battery

or 3.0 to 5.5 V

10 k

CHARGE

TRIGGER

DONE

VIN

GND

0.1 μF

IGBTDRV

A8439

▪ Cell phone flash

▪ Emergency strobe light

4.7 μF

To IGBT Gate

A8439

COUT

OUT

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