Datasheet

LTC4155
14
4155fc
PIN FUNCTIONS
PROG (Pin 18): Charge Current Program and Monitor Pin. A
resistor from PROG to GND programs the maximum battery
charge rate. The LTC4155 features I
2
C programmability
enabling software selection of fifteen charge currents
that are inversely proportional to a single user-supplied
programming resistor.
CHGSNS (Pins 19, 20): Battery Charger Current Sense
Pin. An internal current sense resistor between V
OUT
and CHGSNS monitors battery charge current. CHGSNS
should be connected to the source of an external P-channel
MOSFET transistor.
V
OUT
(Pins 21, 22): Output Voltage of the Switching
PowerPath Controller and Input Voltage of the Battery
Charging System. The majority of the portable product
should be powered from V
OUT
. The LTC4155 will partition
the available power between the external load on V
OUT
and
the battery charger. Priority is given to the external load
and any extra power is used to charge the battery. An
ideal diode control function from BATSNS to V
OUT
ensures
that V
OUT
is powered even if the load exceeds the allotted
power from V
BUS
or if the V
BUS
power source is removed.
V
OUT
should be bypassed with a low impedance multilayer
ceramic capacitor of at least 22µF.
V
BUS
(Pins 23, 24, 25): Input Voltage for the PowerPath
Step-Down Switching Regulator and Output Voltage for
the USB On-The-Go Step-Up Switching Regulator. V
BUS
may be connected to the USB port of a computer or a DC
output wall adapter or to one or both optional overvolt-
age protection/multiplexer compound transistors. V
BUS
should be bypassed with a low impedance multilayer
ceramic capacitor.
SW (Pins 26, 27): Switching Regulator Power Transmis-
sion Pin. The SW pin delivers power from V
BUS
to V
OUT
via the step-down switching regulator and from V
OUT
to
V
BUS
via the step-up switching regulator. A 1H inductor
should be connected from SW to V
OUT
. See the Applica-
tions Information section for a discussion of current rating.
SCL (Pin 28): Clock Input for the I
2
C Serial Port. The
I
2
C input levels are scaled with respect to DVCC for I
2
C
compliance.
GND (Exposed Pad Pin 29): Exposed pad must be soldered
to the PCB to provide a low electrical and thermal imped-
ance connection to the printed circuit board’s ground. A
continuous ground plane on the second layer of a multilayer
printed circuit board is strongly recommended.