LNK302/304-306
LinkSwitch-TN
RF1
D3
L2
D
FB
BP
S
D2
R1
+
C1
AC
INPUT
S
S
L1
C4
C5
C3
R3
DC
OUTPUT
C2
S
D1
D4
Optimize hatched copper areas (
) for heatsinking and EMI.
PI-3750-121106
Figure 6a. Recommended Printed Circuit Layout for LinkSwitch-TN in a Buck Converter Configuration using P or G Package.
D3
L2
RF1
D
S
S
S
S
L1
+
FB
BP
D1
AC
INPUT
C3
C4
C5
D2
C2
DC
OUTPUT
C1
R3
R1
D4
Optimize hatched copper areas (
) for heatsinking and EMI.
PI-4546-011807
Figure 6b. Recommended Printed Circuit Layout for LinkSwitch-TN in a Buck Converter Configuration using D Package
to Bottom Side of the Board.
cycles are skipped. To provide overload protection if no cycles
are skipped during a 50 ms period, LinkSwitch-TN will enter
auto-restart (LNK304-306), limiting the average output power
to approximately 6% of the maximum overload power. Due to
trackingerrorsbetweentheoutputvoltageandthevoltageacross
C3 at light load or no load, a small pre-load may be required
(R4). For the design in Figure 5, if regulation to zero load is
required, then this value should be reduced to 2.4 kΩ.
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 trr ≤75 ns is used for
MDCM operation and for CCM operation, a diode with
trr ≤35 ns is used.
Key Application Considerations
7) The part is board mounted with SOURCE pins soldered
to a sufficient area of copper to keep the SOURCE pin
temperature at or below 100 °C.
LinkSwitch-TN Design Considerations
Output Current Table
*KRP is the ratio of ripple to peak inductor current.
Data sheet maximum output current table (Table 1) represents
the maximum practical continuous output current for both
mostlydiscontinuousconductionmode(MDCM)andcontinuous
conductionmode(CCM)ofoperationthatcanbedeliveredfrom
a given LinkSwitch-TN device under the following assumed
conditions:
LinkSwitch-TN Selection and Selection Between
MDCM and CCM Operation
SelecttheLinkSwitch-TNdevice,freewheelingdiodeandoutput
inductor that gives the lowest overall cost. In general, MDCM
25-5
Rev. I 11/08
POWERINT [ Power Integrations ]
