LT3468/LT3468-1/LT3468-2

10

346812fa

Board Layout

The high voltage operation of the LT3468/LT3468-1/

LT3468-2 demands careful attention to board layout. You

will not get advertised performance with careless layout.

Figure 5 shows the recommended component placement.

Keep the area for the high voltage end of the secondary as

small as possible. Also note the larger than minimum

spacing for all high voltage nodes in order to meet break-

down voltage requirements for the circuit board.

It is

imperative to keep the electrical path formed by C1, the

primary of T1, and the LT3468/LT3468-1/LT3468-2 as

short as possible. If this path is haphazardly made long, it

will effectively increase the leakage inductance of T1,

which may result in an overvoltage condition on the SW

pin.

APPLICATIO S I FOR ATIO

Figure 5. Suggested Layout: Keep Electrical Path Formed by C1,

Transformer Primary and LT3468/LT3468-1/LT3468-2 Short

D2

R1

D1

(DUAL DIODE)

C1

PHOTOFLASH

CAPACITOR

T1

CHARGE

DONE

+

•

4

5

3

2

1

3468 F05

Table 4. Recommended Clamp Diodes

MAX REVERSE VOLTAGE

PART

(V)

VENDOR

ZHCS400

40

Zetex

(631) 360-2222

www.zetex.com

B0540W

40

Diodes Inc.

(805) 446-4800

www.diodes.com

MA2Z720

40

Panasonic

(408) 487-9510

www.panasonic.co.jp

TYPICAL APPLICATIO S

should be a Schottky diode with at least a 500mA peak

forward current capability. The diode forward voltage drop

should be 600mV or less at 500mA of forward current.

Reverse voltage rating should be 40V or higher. Table 4

shows various recommended clamping diodes.

LT3468

CHARGE

GND

SW

+

DONE

DONE

CHARGE

C1

4.7µF

R1

100k

T1

1:10.2

VIN

2.5V TO 8V

320V

1

2

4

5

3468 F06

D2

PHOTOFLASH

CAPACITOR

C1: 4.7µF, 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

D1

LT3468-1

CHARGE

GND

SW

+

DONE

DONE

CHARGE

C1

4.7µF

R1

100k

T1

1:10.2

COUT

PHOTOFLASH

CAPACITOR

VIN

2.5V TO 8V

D2

320V

D1

4

3

5

6

C1: 4.7µF, 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 F07

Figure 6. LT3468 Photoflash Charger Uses

High Efficiency 4mm Tall Transformer

Figure 7. LT3468-1 Photoflash Charger Uses

High Efficiency 3mm Tall Transformer