LNK362-364
TOP VIEW
Y1-
Capacitor
Input Filter
Capacitor
D
S
S
T
r
a
n
s
f
FB
S
S
BP
o
r
m
e
r
-
+
HV DC
INPUT
CBP
Opto-
coupler
Maximize hatched copper
areas (
) for optimum
heatsinking
Output Filter
Capacitor
DC
OUT
-
+
PI-4585-021607
Figure 7. Recommended Printed Circuit Layout for LinkSwitch-XT using D Package in a Flyback Converter Configuration.
capacitor should be minimized. In addition, sufficient copper
area should be provided at the anode and cathode terminals
of the diode for heat sinking. A larger area is preferred at the
quiet cathode terminal. A large anode area can increase high
frequency radiated EMI.
saturationandexcessiveleading-edgecurrentspikesatstartup.
Repeatundersteadystateconditionsandverifythattheleading-
edge current spike event is below ILIMIT(MIN) at the end of the
tLEB(MIN). Under all conditions, the maximum drain 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-XT, transformer, output diode and output
capacitors. Enough thermal margin should be allowed for
part-to-part variation of the RDS(ON) of LinkSwitch-XT as
specifiedinthedatasheet.Underlowline,maximumpower,
a maximum LinkSwitch-XT SOURCE pin temperature of
105 °C is recommended to allow for these variations.
Quick Design Checklist
As with any power supply design, all LinkSwitch-XT 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
650Vatthehighestinputvoltageandpeak(overload)output
power. The 50 V margin to the 700 V BVDSS specification
gives margin for design variation, especially in Clampless
designs.
2. Maximumdraincurrent–Atmaximumambienttemperature,
maximum input voltage and peak output (overload) power,
verify drain current waveforms for any signs of transformer
Design Tools
Up-to-date information on design tools can be found at the
Power Integrations web site: www.powerint.com.
2-7
7
Rev. E 11/08
POWERINT [ Power Integrations ]
