FPF2123 데이터 시트보기 (PDF) - Fairchild Semiconductor

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FPF2123

IntelliMAX™ Advanced Load Management Products

Fairchild Semiconductor 

P(max)=

------------------------t--B---L--A----N---K---(---m-----a----x---)------------------------

tRESTART(min) + tBLANK(max)

×

VI

N

(

m

a

x

)

×

IL

I

M

(

m

a

x

)

(4)

=

-------2---0---------

80 + 20

× 5.5 × 1.5

=

1.65 W

This is more power than the package can dissipate, but the

thermal shutdown of the part will activate to protect the part

from damage due to excessive heating. When using the

FPF2124, attention must be given to the manual resetting of the

part. Continuously resetting the part when a short on the output

is present will cause the temperature of the part to increase.

The junction temperature will only be able to increase to the

thermal shutdown threshold. Once this temperature has been

reached, toggling ON will not turn-on the switch until the

junction temperature drops. For the FPF2125, a short on the

output will cause the part to operate in a constant current state

dissipating a worst case power of,

P(max) = VIN· (max) × ILIM(max)

(5)

= 5.5 × 1.5 = 8.25W

This large amount of power will activate the thermal shutdown

and the part will cycle in and out of thermal shutdown so long as

the ON pin is active and the short is present.

Board Layout

For best performance, all traces should be as short as possible.

To be most effective, the input and output capacitors should be

placed close to the device to minimize the effects that parasitic

trace inductances may have on normal and short-circuit

operation. Using wide traces for VIN, VOUT and GND will help

minimize parasitic electrical effects along with minimizing the

case to ambient thermal impedance.

11

FPF2123-FPF2125 Rev. C4

www.fairchildsemi.com

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