LNK306 データシートの表示（PDF） - Unspecified

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LNK306

Lowest Component Count, Energy-Efficient Off-Line Switcher IC

Unspecified 

LNK302/304-306

AC

INPUT

RF1

D3

L2

C4

C5

D4

LinkSwitch-TN

D

FB

R1

BP

S

S

C1

R3

C3

S

S

D1

D2

+

L1

DC

OUTPUT

C2

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.

AC

INPUT

RF1

D3

C4

D4

L2

C5

D

S

S

L1

+

FB

S

BP

S

D1

C1

C3

R3

R1

D2

C2

DC

OUTPUT

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

tracking errors between the output voltage and the voltage across

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.

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 trr ≤75 ns is used for

MDCM operation and for CCM operation, a diode with

trr ≤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

temperature 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

25-5

Rev. H 12/06

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