BZX100A datasheet(14/24 Pages) LINER

14 / 24 page

LT8300

8300f

applicaTions inForMaTion

A snubber circuit is recommended for most applications.

Two types of snubber circuits shown in Figure 6 that can

protect the internal power switch include the DZ (diode-

Zener)snubberandtheRC(resistor-capacitor)snubber.The

DZ snubber ensures well defined and consistent clamping

voltage and has slightly higher power efficiency, while the

RC snubber quickly damps the voltage spike ringing and

provides better load regulation and EMI performance.

Figure 5 shows the flyback waveforms with the DZ and

RC snubbers.

For the DZ snubber, proper care must be taken when

choosing both the diode and the Zener diode. Schottky

diodes are typically the best choice, but some PN diodes

can be used if they turn on fast enough to limit the leak-

age inductance spike. Choose a diode that has a reverse-

voltage rating higher than the maximum SW pin voltage.

The Zener diode breakdown voltage should be chosen to

balancepowerlossandswitchvoltageprotection.Thebest

compromise is to choose the largest voltage breakdown.

Use the following equation to make the proper choice:

VZENER(MAX) ≤ 150V – VIN(MAX)

For an application with a maximum input voltage of 72V,

choose a 68V Zener diode, the VZENER(MAX) of which is

around 72V and below the 78V maximum.

The power loss in the clamp will determine the power rat-

ing of the Zener diode. Power loss in the clamp is highest

at maximum load and minimum input voltage. The switch

current is highest at this point along with the energy stored

in the leakage inductance. A 0.5W Zener will satisfy most

applications when the highest VZENER is chosen.

Figure 5. Maximum Voltages for SW Pin Flyback Waveform

Figure 6. Snubber Circuits

8300 F05

VSW

tOFF > 350ns

VLEAKAGE

tSP < 250ns

VSW

TIME

No Snubber

with DZ Snubber

with RC Snubber

tOFF > 350ns

VLEAKAGE

tSP < 250ns

TIME

tOFF > 350ns

VLEAKAGE

tSP < 250ns

TIME

<150V

<120V

<150V

<120V

<150V

<120V

8300 F06b

8300 F06a

DZ Snubber

RC Snubber

Lℓ

•

Lℓ

•

BZX100A Datasheet(PDF) 14 Page - Linear Technology

BZX100A Datasheet(HTML) 14 Page - Linear Technology

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

Datasheet Download

Link URL