LT3468/LT3468-1

9

34681i

APPLICATIO S I FOR ATIO

Capacitor Selection

For the input bypass capacitor, a high quality X5R or X7R

type should be used. Make sure the voltage capability of

the part is adequate.

Output Diode Selection

The rectifying diode(s) should be low capacitance type

with sufficient reverse voltage and forward current rat-

ings. The peak reverse voltage that the diode(s) will see is

approximately:

VV

N V

PK R

OUT

IN

()

•

The peak current of the diode is simply:

I

N

PK SEC

−

=

14

.

(LT3468)

I

N

PK SEC

−

=

07

.

(LT3468-1)

Table 3. Recommended Output Diodes

MAX REVERSE VOLTAGE

MAX FORWARD CONTINUOUS CURRENT

CAPACITANCE

PART

(V)

(mA)

(pF)

VENDOR

GSD2004S

2x300

225

5

Vishay

(Dual Diode)

(402) 563-6866

www.vishay.com

BAV23S

2x250

225

5

Philips Semiconductor

(Dual Diode)

(800) 234-7381

www.philips.com

1SS306

2x250

100

3

Toshiba

(Dual Diode)

(949) 455-2000

www.semicon.toshiba.co.jp

recommended for most LT3468/LT3468-1 applications.

Another option is to use the BAV23S dual silicon diodes.

Toshiba makes a dual diode named 1SS306 which also

meets all the requirements. Table 3 shows the various

diodes and relevant specifications. Use the appropriate

number of diodes to achieve the necessary reverse break-

down voltage.

SW Pin Clamp Diode Selection

The diode D2 in Figure 1 is needed to clamp the SW node.

Due to the new control scheme of the LT3468/LT3468-1,

the SW node may go below ground during a switch cycle.

The clamp diode prevents the SW node from going too

far below ground. The diode is required for proper opera-

tion of the circuit. The recommended diode should be a

Schottky diode with at least a 500mA peak forward current

capability. Reverse voltage rating should be 40V or higher.

Table 4 shows various recommended clamping diodes.

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