Datasheet

© 2007 Fairchild Semiconductor Corporation www.fairchildsemi.com
FPF1003A / FPF1004 • Rev. 1.0.6 9
FPF1003A / FPF1004 — IntelliMAX™ Advanced Load Management Products
Description of Operation
Input Capacitor
FPF1003A and FPF1004 are low-RDS(ON) P-channel
load switches with controlled turn-on. The core of each
device is a 30 mΩ P-Channel MOSFET and a controller
capable of functioning over an input operating range of
1.2 to 5.5 V. Switch control is accomplished with a logic
input (ON) capable of interfacing directly with low-
voltage control signal. In FPF1004, a 120 Ω on-chip load
resistor is added for output quick discharge when the
switch is turned off.
Application Information
Figure 24. Typical Application
Input Capacitor
To limit the voltage drop on the input supply caused by
transient inrush currents when the switch turns on into a
discharged load capacitor or short-circuit, a capacitor
needs to be placed between V
IN
and GND. A 0.1 μF
ceramic capacitor, C
IN
, must be placed close to the V
IN
pin. A higher value of C
IN
can be used to further reduce
the voltage drop experienced as the switch is turned on
into a large capacitive load.
Output Capacitor
A 0.1 μF capacitor, C
OUT
, should be placed between
VOUT and GND. This capacitor prevents parasitic board
inductance from forcing V
OUT
below GND when the
switch turns off. Due to the integral body diode in the
PMOS switch, a C
IN
greater than C
OUT
is 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
.
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 minimizes the
parasitic electrical effects and case-to-ambient thermal
impedance.