LTC4232 datasheet(16/20 Pages) LINER

16 / 20 page

LTC4234

4234fa

For more information www.linear.com/LTC4234

APPLICATIONS INFORMATION

Figure 6. The second layer is 1oz copper connected to

the vias to the SENSE pad on the top layer. Two versions

of the second layer are considered. One uses a minimum

sized SENSE pad that only covers the vias for the top

layer while the remainder of the second layer is empty

(see Figure 7). The other version fills the second layer

with SENSE connected copper (see Figure 8). The third

layer is 1oz copper tied to ground while the bottom layer

is 2oz copper tied to ground except for a few signal traces.

The curves demonstrate that the heat from the MOSFET

can be effectively transferred out of the package through

the OUT pins and only requires a minimum sized SENSE

pad under the package. However for small boards the

larger SENSE area does reduce the junction temperature

when sourcing higher currents.

Additional Applications

TheLTC4234hasawideoperatingrangefrom2.9Vto15V.

The UV, OV and PG thresholds are set with few resistors.

All other functions are independent of supply voltage.

In addition to Hot Swap applications, the LTC4234 also

functions as a backplane resident switch for removable

load cards (see Figure 9).

Figure 10 shows a 3.3V application with a UV threshold

of 2.87V, an OV threshold of 3.77V and a PG threshold

of 3.05V.

The last page shows a 40A parallel application where the

two LTC4234 parts each provide 20A to the load. The

PNPs prevent one LTC4234 from faulting off in current

limit until both parts hit the 22.5A limit. The PNPs are

disconnected when power good is false via the series

MOSFETs M1 and M2

Figure 7. Temperature Rise for Small SENSE Pad

Figure 8. Temperature Rise for Large SENSE Pad

∆TJB

100

120

10A

15A

20A

4234 F07

100

4234 F07

SMALL SENSE PAD (2ND LAYER)

∆TJB

100

120

10A 15A

100

20A

4234 F08

LARGE SENSE PAD (2ND LAYER)

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