Datasheet

LTC3553
13
3553fb
PIN FUNCTIONS
BAT (Pin 17): Single-Cell Li-Ion Battery Pin. Depending
on available power and load, a Li-Ion battery on BAT will
either deliver system power to V
OUT
through the ideal
diode or be charged from the battery charger.
V
OUT
(Pin 18): Output Voltage of the PowerPath Controller
and Input Voltage of the Battery Charger. The majority of
the portable products should be powered from V
OUT
. The
LTC3553 will partition the available power between the
external load on V
OUT
and the internal battery charger.
Priority is given to the external load and any extra power
is used to charge the battery. An ideal diode from BAT to
V
OUT
ensures that V
OUT
i s p o w e r e d e v e n i f t h e l o a d e x c e e d s
the allotted input current from V
BUS
or if the V
BUS
power
source is removed. V
OUT
should be bypassed with a low
impedance multilayer ceramic capacitor.
SUSP (Pin 19): Suspend Mode Logic Input. If this pin
is driven high the input current limit path is disabled.
In this state the circuit draws negligible power from the
V
BUS
pin. Any load at the V
OUT
pin is provided by the
battery through the internal ideal diode. When this input
is grounded, the input current limit will be set to desired
value as determined by the state of the HPWR pin. This
pin has a conditional internal pull-down resistor when
power is applied to the V
BUS
pin.
V
BUS
(Pin 20): USB Input Voltage. V
BUS
will usually be
connected to the USB port of a computer or a DC output
wall adapter. V
BUS
should be bypassed with a low imped-
ance multilayer ceramic capacitor.
GND (Exposed Pad Pin 21): Ground. The exposed pack-
age pad is ground and must be soldered to the PC board
for proper functionality and for maximum heat transfer.