LNK353/354

F

2/05

6

of the diode for heatsinking. A larger area is preferred at the

quiet cathode terminal. A large anode area can increase high

frequency radiated EMI.

Quick Design Checklist

As with any power supply design, all LinkSwitch-HF designs

should be verified on the bench to make sure that component

specificationsarenotexceededunderworst-caseconditions.The

following minimum set of tests is strongly recommended:

1. Maximum drain voltage – Verify that V

675Vatthehighestinputvoltageandpeak(overload)output

power.

2. Maximumdraincurrent–Atmaximumambienttemperature,

maximum input voltage and peak output (overload) power,

verify drain current waveforms for any signs of transformer

saturation and excessive leading edge current spikes at

startup. Repeat under steady state conditions and verify that

Figure 6. Recommended Printed Circuit Layout for LinkSwitch-HF in a Flyback Converter Configuration.

the leading edge current spike event is below I

end of the t

current should be below the specified absolute maximum

ratings.

3. Thermal Check – At specified maximum output power,

minimuminputvoltageandmaximumambienttemperature,

verify that the temperature specifications are not exceeded

for LinkSwitch-HF, transformer, output diode, and output

capacitors. Enough thermal margin should be allowed for

part-to-part variation of the R

specifiedinthedatasheet.Underlowline,maximumpower,

a maximum LinkSwitch-HF SOURCE pin temperature of

100 °C is recommended to allow for these variations.

Design Tools

Up-to-date information on design tools can be found at the

Power Integrations website: www.powerint.com.

+

HV DC

Input

PI-3890-102704

Input Filter

Capacitor

-

DC

Out

Output Filter

Capacitor

Y1-

Capacitor

Maximize hatched copper

areas (

) for optimum

heatsinking

TOP VIEW

D

S

S

BP

FB

S

S

LinkSwitch-HF

+

-

Opto-

coupler

PRI

SEC

T

r

a

n

s

f

o

r

m

e

r