Datasheet

8
LNK302/304-306
G
3/05
be included for better EMI performance and higher line surge
withstand capability.
Quick Design Checklist
As with any power supply design, all
LinkSwitch-TN designs
should be verified for proper functionality on the bench. The
following minimum tests are recommended:
1) Adequate DC rail voltage – check that the minimum DC
input voltage does not fall below 70 VDC at maximum load,
minimum input voltage.
2) Correct Diode Selection – UF400x series diodes are
recommended only for designs that operate in MDCM at
an ambient of 70 °C or below. For designs operating in
continuous conduction mode (CCM) and/or higher ambients,
then a diode with a reverse recovery time of 35 ns or better,
such as the BYV26C, is recommended.
3) Maximum drain current – verify that the peak drain current
is below the data sheet peak drain specification under
worst-case conditions of highest line voltage, maximum
overload (just prior to auto-restart) and highest ambient
temperature.
4) Thermal check – at maximum output power, minimum
input voltage and maximum ambient temperature, verify
that the LinkSwitch-TN SOURCE pin temperature is
100 °C or below. This figure ensures adequate margin due
to variations in R
DS(ON)
from part to part. A battery powered
thermocouple meter is recommended to make measurements
when the SOURCE pins are a switching node. Alternatively,
the ambient temperature may be raised to indicate margin
to thermal shutdown.
In a LinkSwitch-TN design using a buck or buck boost converter
topology, the SOURCE pin is a switching node. Oscilloscope
measurements should therefore be made with probe grounded
to a DC voltage, such as primary return or DC input rail, and
not to the SOURCE pins. The power supply input must always
be supplied from an isolated source (e.g. via an isolation
transformer).