Datasheet

Rev. J 06/13
5
LNK302/304-306
www.powerint.com
+
PI-3750-041509
C2
L1
L2
R1
R3
RF1 D3
D4
D2
D1
C1
C3C5C4
Optimize hatched copper areas ( ) for heatsinking and EMI.
D
S
S
FB
BP
S
S
LinkSwitch-TN
AC
INPUT
DC
OUTPUT
AC
INPUT
+
DC
OUTPUT
PI-4546-041509
Optimize hatched copper areas ( ) for heatsinking and EMI.
S
S
S
S
BP
FB
D1
C2
R3
RF1
D3
D4
D2
R1
C1
C4 C5
C3
LinkSwitch-TN
L2
L1
D
Figure 6a. Recommended Printed Circuit Layout for LinkSwitch-TN in a Buck Converter Configuration using P or G Package.
Key Application Considerations
LinkSwitch-TN Design Considerations
Output Current Table
Data sheet maximum output current table (Table 1) represents
the maximum practical continuous output current for both
mostly discontinuous conduction mode (MDCM) and continuous
conduction mode (CCM) of operation that can be delivered
from a given LinkSwitch-TN device under the following
assumed conditions:
1. Buck converter topology.
2. The minimum DC input voltage is ≥70 V. The value of input
capacitance should be large enough to meet this criterion.
3. For CCM operation a KRP* of 0.4.
4. Output voltage of 12 VDC.
5. Efficiency of 75%.
6. A catch/freewheeling diode with t
RR
≤75 ns is used for MDCM
operation and for CCM operation, a diode with t
RR
≤35 ns is
used.
7. The part is board mounted with SOURCE pins soldered to a
sufficient area of copper to keep the SOURCE pin tempera-
ture at or below 100 °C.
*KRP is the ratio of ripple to peak inductor current.
LinkSwitch-TN Selection and Selection Between
MDCM and CCM Operation
Select the LinkSwitch-TN device, freewheeling diode and
output inductor that gives the lowest overall cost. In general,
MDCM provides the lowest cost and highest efficiency converter.
CCM designs require a larger inductor and ultrafast (t
RR
≤35 ns)
freewheeling diode in all cases. It is lower cost to use a larger
LinkSwitch-TN in MDCM than a smaller LinkSwitch-TN in CCM
because of the additional external component costs of a CCM
design. However, if the highest output current is required, CCM
should be employed following the guidelines below.
Topology Options
LinkSwitch-TN can be used in all common topologies, with or
without an optocoupler and reference to improve output voltage
tolerance and regulation. Table 2 provide a summary of these
configurations. For more information see the Application Note
– LinkSwitch-TN Design Guide.
Figure 6b. Recommended Printed Circuit Layout for LinkSwitch-TN in a Buck Converter Configuration using D Package to Bottom Side of the Board.