FPF2172 데이터 시트보기 (PDF) - Fairchild Semiconductor

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FPF2172

IntelliMAX™ Advanced Load Management Products

Fairchild Semiconductor 

Application Information

Typical Application

Battery

5.5V

VIN

OFF ON

ON

C1 = 4.7µF 5.5V MAX

VOUT

FPF2172

FLAGB

GND

R1 = 100KΩ

C2 = 0.1µF

R2 = 110Ω

Input Capacitor

To limit the voltage drop on the input supply caused by transient

in-rush currents when the switch turns-on into a discharged load

capacitor or a short-circuit, a capacitor needs to be placed

between VIN and GND. A 4.7µF ceramic capacitor, CIN, must be

placed close to the VIN pin. A higher value of CIN can be used to

further reduce the voltage drop experienced as the switch is

turned on into a large capacitive load.

Output Capacitor

A 0.1uF capacitor COUT, should be placed between VOUT and

GND. This capacitor will prevent parasitic board inductances

from forcing VOUT below GND when the switch turns-off.

Power Dissipation

During normal operation as a switch, the power dissipation is

small and has little effect on the operating temperature of the

part. The parts with the higher current limits will dissipate the

most power and that will only be typically,

P = ILIM × VDROP = 0.4 × 0.4 = 160mW

(1)

When using the part, attention must be given to the manual

resetting of the part. Continuously resetting the part at a high

duty cycle when a short on the output is present can cause the

temperature of the part to increase. The junction temperature

will only be allowed 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.

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.

FPF2172 Rev. I

9

www.fairchildsemi.com

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