LinkSwitch-HP
Layout Considerations for eDIP-12B package
Quick Design Checklist
The schematic extract in Figure 13 is an example of LinkSwitch-HP
used in a dual output LCD monitor supply using eDIP-12B
package. In this design the exposed metal tab on the topside
of package is left open (no heat sink). The SOURCE pins of
LinkSwitch-HP provide heat sinking through connection to the
source copper pad of PCB. This technique is adequate for
device dissipation up to 0.85 W (1/2 square inch of copper area
required). The layout guidelines described for eSIP-7C are the
same for eDIP-12B with an added consideration about sensitive
component layout. The return referenced components C4, C8,
C16, R9, R7 must be placed directly under the LinkSwitch-HP
package as shown in Figure 14. This requires that these
particular components be SMD type as this allows an ideal
noise-immune layout.
All LinkSwitch-HP designs should be verified on the bench
particularly for specified worst-case stress conditions. The
following set of tests are strongly recommended:
1. Maximum drain voltage – Verify that VDS does not exceed
675 V for LNK677X series and 600 V for LNK6X6X series.
This gives a 50 V margin for design variations.
2. Under all conditions, the maximum Drain current should be
below the specified absolute maximum ratings.
3. Thermal check – At rated maximum output power, minimum
input voltage and maximum ambient temperature, verify that
the maximum allowed temperature is not exceeded for any
component in the design. Of particular importance is
checking the temperature rise of the major power conversion
components such as transformer, output diodes, input
bridge, primary clamp circuit and LinkSwitch-HP. Under the
stated conditions above, LinkSwitch-HP tab temperature
should not exceed 110 °C.
Output Power Table Assumptions
• 12 V output.
• Schottky rectification.
• 82% efficiency.
• VOR = 135 V.
D
S
BP
• KP = 0.4 for 85-265 VAC input and KP = 0.6 for 195-265 VAC
input.
• VMIN = 100 V for 85-265 VAC input and VMIN = 250 V for
195-265 VAC input.
LinkSwitch-HP
U1
LNK6774V
CONTROL
FB
C5
PD CP
4.7 µF
10 V
C16
10 pF
50 V
R9
R7
10.5 kΩ
1%
• 0.85 W device dissipation for open frame designs with PCB
heat sink.
100 kΩ
1%
R6
1/16 W
1/16 W
23.2 kΩ
1%
C8
100 pF
50 V
C4*
C7
100 nF
25 V
1/16 W
PI-6860-120312
*Optional
Figure 13. 17 W LCD Monitor Supply (+18 V, +5 V).
Figure 14. Layout for LCD Monitor Supply Using eDIP-12B Package.
11
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Rev. C 03/14
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