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FPF2100-FPF2107 Rev. D2
F
Application Information
Typical Application
OFF ON
ON
V
IN
GND
FPF2100 - FPF2107
FLAGB
V
OUT
LOAD
Battery
1.8V-5.5V
C1 = 10
μ
F
R1 = 100K
C2 = 0.1
μ
F
R2 = 499
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 V
IN
and GND. A 0.1uF ceramic capacitor, C
IN
, placed
close to the pins is usually sufficient. Higher values of C
IN
can
be used to further reduce the voltage drop.
Output Capacitor
A 0.1uF capacitor C
OUT
, should be placed between V
OUT
and
GND. This capacitor will prevent parasitic board inductances
from forcing V
OUT
below GND when the switch turns-off. For
the FPF2100-FPF2102 and the FPF2104-FPF2106, the total
output capacitance needs to be kept below a maximum value,
C
OUT
(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,
Due to the integral body diode in the PMOS switch, a C
IN
greater than C
OUT
is highly recommended. A C
OUT
greater
than C
IN
can cause V
OUT
to exceed V
IN
when the system
supply is removed. This could result in current flow through the
body diode from V
OUT
to V
IN
.
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 typically be,
If the part goes into current limit the maximum power dissipation
will occur when the output is shorted to ground. For the
FPF2100, FPF2101, FPF2104 and FPF2105, the power
dissipation will scale by the Auto-Restart Time, t
RSTRT
, and the
Over Current Blanking Time, t
BLANK
, so that the maximum
power dissipated is typically,
When using the FPF2102 and FPF2106 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. For the FPF2103 and FPF2107, a short on
the output will cause the part to operate in a constant current
state dissipating a worst case power as calculated in (3) until
the thermal shutdown activates. It will then 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 V
IN
, V
OUT
and GND will help
minimize parasitic electrical effects along with minimizing the
case to ambient thermal impedance.
IN
BLANK
LIM
OUT
V
(min)
t
(max)
I
(max)
C
=
80mW
0.125
(0.8)
R
)
(I
=
2
2
DS
LIM
=
=
(max)
I
(max)
V
t
t
t
P(max)
LIM
IN
BLANK
RETRY
BLANK
+
10
+
=
260mW
0.8
5.5
160
10
=
=
(1)
(2)
(3)