To IGBT Gate

k

COUT

D1

T1

R1

R2

R3

R4

100 k

R5

10

One Li+ battery

or 3.0 to 5.5 V

C2

4.7 μF

C1

0.1 μF

2.0 A

1.8 A (N.C.)

1.6 A

A8438

GND

FB

SW

IGBTDRV

VIN

10 k

R6

10 k

R7

CHARGE

TRIGGER

DONE

ILIM

Approximate Scale 1:1

Figure 1. Typical circuit with separate power supply to transformer

Figure 2. Typical circuit with single power supply

2.0 A

1.8 A (N.C.)

1.6 A

To IGBT Gate

k

COUT

D1

T1

R1

R2

R3

R4

100 k

R5

10

Two Alkaline/NiMH/NiCAD or one Li+ battery

or 1.5 to 5.5 V

C2

4.7 μF

C1

0.1 μF

A8438

GND

FB

SW

IGBTDRV

VIN

10 k

R6

10 k

R7

CHARGE

TRIGGER

DONE

ILIM

A8438-DS, Rev. 2

Description

The A8438 is a highly integrated IC that charges photoflash

capacitors for digital and film cameras. It also features an

integrated IGBT driver that facilitates the flash discharge

function and saves board space.

To charge the photoflash capacitor, the A8438 integrates a

40 V, DMOS switch that drives the transformer in a flyback

topology, allowing optimized design with tight coupling and

high efficiency. A proprietary control scheme optimizes the

capacitor charging time. Low quiescent current and low

shutdown current further improve system efficiency and

extend battery life.

Three levels of switch current limit are provided: 1.6, 1.8,

and 2.0 A. The level is determined by configuring the ILIM

pin as grounded, floating, or pulled up to IC supply voltage,

respectively.

The CHARGE pin enables the A8438 and starts the charging

of the output capacitor. When the designated output voltage

is reached, the A8438 stops the charging until the CHARGE

pin is toggled again. Pulling the CHARGE pin low stops

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

the designated output voltage is reached.

TheA8438canbeusedwithtwoAlkaline/NiMH/NiCADorone

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 A8438 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.

Features and Benefits

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

▪ Adjustable output voltage

▪ >75% efficiency

▪ Three levels of switch current limit: 1.6, 1.8, 2.0 A

▪ Fast charge time

▪ Charge complete indication

▪ Integrated IGBT driver with trigger

▪ No primary-side Schottky diode needed

▪ Low-profile package (0.75 mm nominal height)

Photoflash Capacitor Charger with IGBT Driver

A8438

Package: 10 pin TDFN/MLP (suffix EJ)

Typical Applications