Operation and Application Information
The FPF3003 is a low-RON, P-channel-based, input-
source-selection power management switch for dual-
battery systems. The FPF3003 input operating range is
from 2.3V to 5.5V on BATA and BATB, while ADPIN has
a range of 4.6V to 5.5V.
The FPF3003 controls the charging path from the
charger to the battery with up to 1.5A and the
discharging path from the battery to system load with up
to 2.5A. The system or PMIC selects one of two
batteries to provide power and enables one of the
batteries to be charged by the external battery charger.
The FPF3003 has 30µs slew-rate control to reduce
inrush current when engaged and thermal shutdown
protection for reliable system operation.
The internal circuit is powered from the highest voltage
source among BATA, BATB, and ADPIN.
Battery Presence Detection
The FPF3003 monitors whether or not a battery is
present via the BATAID and BATBID pins. If any of
these pins are LOW; FPF3003 recognizes the battery is
present. Each pin is connected with an internal LDO
output, so no pull-up resistor is required.
During battery source transition, voltage droop depends
on output capacitance and load current condition.
Advanced break-before-make operation minimizes the
droop with minimum capacitance. At least 10µF is a
good starting value in design.
Primary Battery Under-Voltage Set
FPF3003 monitors the primary battery of BATA for
under-voltage condition. Once under-voltage condition
is confirmed, the system power source changes from
BATA to valid BATB automatically.
The under-voltage threshold level can be programmed
with 0.8V of LOBAT and R divider (R1 and R2) as:
where BATA_LO = Low BATA threshold to set.
If 3.4V of BATA is desired, R1/R2=3.25. If R2 is chosen
1MΩ, R1 is 3.25MΩ. Higher R2 is recommended to
reduce leakage current from BATA.
The load path can be controlled by the BATSEL pin.
When BATSEL is LOW, the system is powered from
BATA. When BATSEL is HIGH, BATB powers the system.
Figure 36 is state diagram showing how the power path
from battery to system is determined.
from ADPIN, BATA, or BATB
RESETB = HIGH
Switch to the present battery
Either BATAID or
BATBID = HIGH
Both BATAID and
BATBID = LOW
LOBAT > 0.8V
BATSEL = LOW
Switch to BATB
Switch to BATA
Figure 36. Power Path from Battery to System
The open-drain STAT pin is used to determine which
battery powers the system. STAT becomes LOW if
BATB is connected to the system. STAT is HIGH (HI-Z)
if BATA is connected.
Figure 35. BATA Under-Voltage Level Setting
LOBAT has a 1.3ms of deglitch time to ensure BATA is
in true under-voltage rather than transient battery
voltage drop during GSM transmission operation.
© 2011 Fairchild Semiconductor Corporation
FPF3003 • Rev. 1.0.0