LNK353/354
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.
the leading edge current spike event is below ILIMIT(MIN)at the
endofthetLEB(MIN). Underallconditions, themaximumdrain
current should be below the specified absolute maximum
ratings.
Quick Design Checklist
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 RDS(ON) of LinkSwitch-HF as
specifiedinthedatasheet.Underlowline,maximumpower,
a maximum LinkSwitch-HF SOURCE pin temperature of
100 °C is recommended to allow for these variations.
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 VDS does not exceed
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
Design Tools
Up-to-date information on design tools can be found at the
Power Integrations website: www.powerint.com.
Input Filter
Capacitor
TOP VIEW
Y1-
Capacitor
+
T
r
a
n
s
f
HV DC
Input
+
DC
Out
-
-
o
r
m
e
r
Output Filter
Capacitor
PRI
SEC
D
S
S
LinkSwitch-HF
Opto-
coupler
Maximize hatched copper
S
S
BP
FB
areas (
) for optimum
heatsinking
PI-3890-102704
CBP
Figure 6. Recommended Printed Circuit Layout for LinkSwitch-HF in a Flyback Converter Configuration.
F
2/05
6
POWERINT [ Power Integrations ]
