© 2012 Fairchild Semiconductor Corporation www.fairchildsemi.com
FPF3040 • Rev. 2.4.3 11
FPF3040 — IntelliMAX™ 18 V-Rated Dual Input Single Output Power-Source-Selector Switch
Operation and Application Information
The FPF3040 is a 18 V, 2 A-rated, Dual-Input Single-
Output (DISO) load switch with slew-rate-controlled,
low-on-resistance, based-on-N-channel MOSFET. The
input operating range is from 4 V to 6.5 V at VBUS and
from 4 V to 10.5 V at VIN. The internal circuitry is
powered from the highest voltage source among VIN,
VBUS, and VEN.
Input Power Source Selection
Input power source can be selected by VIN_SEL and
DF_IN, respectively, depending on EN state. When EN
is HIGH, the input source is selected by VIN_SEL
regardless of DF_IN. If VIN_SEL is LOW, VBUS is selected.
If VIN_SEL is HIGH, VIN is selected.
Table 2. Input Power Selection by VIN_SEL
When EN is LOW, the input source is selected by
DF_IN and the number of valid input sources. If only
one input source is valid, or more than UVLO, the
source is selected automatically, regardless of DF_IN,
to make a charging path in case the battery is depleted.
If both VBUS and VIN have valid input sources, the input
source is selected by DF_IN. If DF_IN is LOW, VIN is
selected. If DF_IN is HIGH or floating, VBUS is selected.
DF_IN is biased HIGH with an internal 1 µA pull-up
current source.
Table 3. Input Power Selection by DF_IN
VIN_SEL can be the status output to indicate which input
power source is used during EN is LOW. If VIN is used,
VIN_SEL shows high. If VBUS is used, VIN_SEL shows LOW.
The voltage level of HIGH signal is 5.3 V if any one of
VIN, VBUS or EN is higher than 5.3 V. The signal is
highest voltage among VIN, VBUS, and VEN if none of
them is higher than 5.3 V.
EN Voltage for Control Logic Power
Supply
Internal control logic is powered from the highest
voltage among VIN, VBUS, and VEN. If valid VIN or VBUS
higher than UVLO is applied, ON/OFF control by EN
should be accomplished with VIH/VIL. If EN powers the
internal control block without valid VIN and VBUS, more
than 2.5 V is required on the EN pin to operate properly.
Over-Voltage Protection (OVP)
FPF3040 has over-voltage protection at both VIN and
VBUS. If VIN or VBUS is higher than 12 V or 7.5 V,
respectively, the power switch is off until input voltage is
lower than the over-voltage trip level by hysteresis
voltage of 0.5 V.
Reverse Power Supply for OTG
FPF3040 has a bi-directional switch so reverse power is
allowed for On-The-Go (OTG) operation. Even if both VIN
and VBUS are not available, reverse power can be also
supported if internal control circuitry is powered by EN.
Reverse-Current Blocking
FPF3040 supports reverse-current blocking during EN
LOW and an unselected channel.
Thermal Shutdown
During FPF3040 thermal shutdown, the power switch is
turned off if junction temperature reaches over 150°C to
avoid damage.
Wireless Charging System
FPF3040 can be used for an input power selector
supporting Travel Adaptor (TA) and Wireless Charging
(WC) with a single-input-based battery charger or Power
Management IC (PMIC), including a charging block as
shown in Figure 31. The system can recognize an input
power source change between 5 V TA and 5 V WC
without detection circuitry because FPF3040 has a
100 ms transition delay. OTG Mode can be supported
without an additional power path, such as a MOSFET.
Travel Adaptor
(5V)
Wireless Charging
(5V)
FPF3040
Li-Pol
BAT
System
PMIC
with
BAT Charger &
OTG Boost &
Power Path
VBUS
VIN
VOUT
EN, VIN_SEL, DF_IN
VIN_SEL, Other_VIN_Ava
Figure 31. Block Diagram of Input Power Selector for Wireless Charging System