© 2013 Semiconductor Components Industries, LLC. www.fairchildsemi.com
FPF3042 • Rev. 1.0.1 12 www.onsemi.com
FPF3042 — IntelliMAX™ 18 V-Rated, Dual-Input, Single-Output, Power-Source-Selector Switch
Operation and Application Information
The FPF3042 is an 18 V, 2.7 A-rated, Dual-Input Single-
Output (DISO) N-channel MOSFET load switch with
slew-rate-controlled and low on resistance. The input
operating range is from 4 V to 12.4 V at VBUS and at VIN.
The internal circuitry is powered from the highest
voltage source among VIN, VBUS, and EN.
Input Power-Source Selection
The input power source can be selected by VIN_SEL and
DF_IN, respectively, depending on the 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 (greater than VUVLO(MAX)), the
source is selected automatically, regardless of DF_IN,
to make 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 EN 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)
The FPF3042 includes over-voltage protection at both VIN
and VBUS. If VIN or VBUS is higher than 14 V (typical), the
power switch is off until input voltage is lower than the
over-voltage trip level by a hysteresis voltage of 0.5 V.
Reverse Power Supply for OTG
The bidirectional switch allows reverse power for On-The-
Go (OTG) operation. Even if both VIN and VBUS are
unavailable, reverse power can be supported if internal
control circuitry is powered by EN.
Reverse-Current Blocking (RCB)
FPF3042 supports reverse-current blocking during EN
LOW and an unselected channel.
Thermal Shutdown
During thermal shutdown, the power switch is turned off
if junction temperature exceeds 150°C to avoid damage.
Wireless Charging System
FPF3042 can be used as 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 FPF3042 has a
100 ms transition delay. OTG Mode can be supported
without an additional power path, such as a MOSFET.
Travel Adaptor
Wireless Charging
FPF3042
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. Input Power Selector for Wireless Charging System