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FPF2163 View Datasheet(PDF) - Fairchild Semiconductor

Part Name
Description
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FPF2163 Datasheet PDF : 13 Pages
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Application Information
Typical Application
Battery
1.8V-5.5V
OFF ON
C1 = 0.1µF
VIN FPF2163/4/5VOUT
FLAGB
ON
ISET
GND
LOAD
C2 = 0.1µF
RSET
R2 = 499
Setting Current Limit
The FPF2163, FPF2164, and FPF2165 have a current limit
which is set with an external resistor connected between ISET
and GND. This resistor is selected by using the following
equation,
RSET
=
2----7---5---.--6--
ILIM
(2)
RSET is in Ohms and that of ILIM is Amps
The table below can also be used to select RSET. A typical
application would be the 500mA current that is required by a
single USB port. Using the table below an appropriate selection
for the RSET resistor would be 394. This will ensure that the
port load could draw 525mA, but not more than 875mA.
Likewise for a dual port system, an RSET of 185would always
deliver at least 1125mA and never more than 1875mA
Current Limit Various RSET Values
RSET
[]
Min. Current Typ. Current Max. Current
Limit
Limit
Limit
[mA]
[mA]
[mA]
185
1125
1500
1875
220
938
1250
1562
275
750
1000
1250
306
675
900
1125
345
600
800
1000
394
525
700
875
460
450
600
750
550
375
500
625
610
338
450
563
690
300
400
500
790
263
350
438
920
225
300
375
1100
188
250
313
1380
150
200
250
1830
113
150
188
Input Capacitor
To limit the voltage drop on the input supply caused by transient
in-rush currents when the switch is turned on into a discharged
load capacitor or a short-circuit, a capacitor needs to be placed
between VIN and GND. A 0.1uF ceramic capacitor, CIN, placed
close to the pins is usually sufficient. Higher values of CIN can
be used to further reduce the voltage drop.
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. For the
FPF2163 and FPF2164, the total output capacitance needs to
be kept below a maximum value, COUT(max), to prevent the
part from registering an over-current condition and turning-off
the switch. The maximum output capacitance can be
determined from the following formula,
COUT(max)
=
I--L----I--M------(--m------a----x---)---×-----t--B-----L---A-----N-----K----(---m-----i--n----)
VIN
(1)
Power Dissipation
During normal operation as a switch, the power dissipated in the
part will depend upon the level at which the current limit is set.
The maximum allowed setting for the current limit is 1.5A and
this will result in a power dissipation of,
P = (ILIM)2 × RDS = (1.5)2 × 0.12 = 270mW (2)
If the part goes into current limit the maximum power dissipation
will occur when the output is shorted to ground. For the
FPF2163, the power dissipation will scale by the Auto-Restart
Time, tRSTRT, and the Over Current Blanking Time, tBLANK, so
that the maximum power dissipated is,
P(max)
=
----------------t--B----L----A----N-----K------------------
tBLANK + tRSTRT
×
VIN(m
ax
)
×
ILIM(
m
ax
)
=
---------3---0----------
30 + 450
×
5.5
×
1.5
=
515.6 m W
(3)
10
FPF2163/4/5 Rev. C3
www.fairchildsemi.com
 

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