LT3468/LT3468-1

1

34681i

TYPICAL APPLICATIO S

Information furnished by Linear Technology Corporation is believed to be accurate and reliable.

However, no responsibility is assumed for its use. Linear Technology Corporation makes no represen-

tation that the interconnection of its circuits as described herein will not infringe on existing patent rights.

Final Electrical Specifications

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Digital / Film Camera Flash

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PDA / Cell Phone Flash

s

Emergency Strobe

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Highly Integrated IC Reduces Solution Size

s

Uses Small Transformers:

5.8mm

× 5.8mm × 3mm

s

Fast Photoflash Charge Times:

4.6s for LT3468 (0V to 320V, 100

5.5s for LT3468-1 (0V to 320V, 50

s

Controlled Input Current:

500mA (LT3468)

225mA (LT3468-1)

s

Supports Operation from Single Li-Ion Cell, or Any

Supply from 2.5V up to 16V

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Adjustable Output Voltage

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No Output Voltage Divider Needed

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Charges Any Size Photoflash Capacitor

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Low Profile (1mm) SOT-23 Package

APPLICATIO S

FEATURES

DESCRIPTIO

Photoflash Capacitor

Charger in ThinSOT

TM

October 2003

The LT

to charge photoflash capacitors in digital and film cam-

eras. A new control technique* allows for the use of

extremely small transformers. Each device contains an

on-chip high voltage NPN power switch. Output voltage

detection* is completely contained within the device,

eliminating the need for any discrete zener diodes or

resistors. The output voltage can be adjusted by simply

changing the turns ratio of the transformer. The LT3468

has a primary current limit of 1.4A while the LT3468-1 has

a 0.7A limit. These different current limit levels result in

well controlled input currents of 500mA for the LT3468

and 225mA for the LT3468-1. Aside from the differing

current limit, the two devices are otherwise equivalent.

The CHARGE pin gives full control of the part to the user.

Driving CHARGE low puts the part in shutdown. The DONE

pin indicates when the part has completed charging. The

LT3468 series of parts are housed in tiny low profile

(1mm) SOT-23 packages.

, LTC and LT are registered trademarks of Linear Technology Corporation.

ThinSOT is a trademark of Linear Technology Corporation. *U.S. Patent # 6, 518, 733

DANGER HIGH VOLTAGE – OPERATION BY HIGH VOLTAGE TRAINED PERSONNEL ONLY

Figure 1. LT3468 Photoflash Charger Uses

High Efficiency 4mm Tall Transformer

LT3468

CHARGE

GND

SW

+

DONE

DONE

CHARGE

C1

4.7

µF

R1

100k

T1

1:10.2

COUT

PHOTOFLASH

CAPACITOR

VIN

2.5V TO 8V

D2

320V

D1

1

2

4

5

C1: 4.7

µF, X5R OR X7R, 10V

D1: VISHAY GSD2004S DUAL DIODE CONNECTED IN SERIES

D2: ZETEX ZHCS400 OR EQUIVALENT

R1: PULL UP RESISTOR NEEDED IF DONE PIN USED

3468 TA01

Figure 2. LT3468-1 Photoflash Charger Uses

High Efficiency 3mm Tall Transformer

LT3468-1

CHARGE

GND

SW

+

DONE

DONE

CHARGE

C1

4.7

µF

R1

100k

T1

1:10.2

COUT

PHOTOFLASH

CAPACITOR

VIN

2.5V TO 8V

D2

320V

D1

4

3

5

6

C1: 4.7

µF, X5R OR X7R, 10V

D1: VISHAY GSD2004S DUAL DIODE CONNECTED IN SERIES

D2: ZETEX ZHCS400 OR EQUIVALENT

R1: PULL UP RESISTOR NEEDED IF DONE PIN USED

3468 TA02