LTC4055/LTC4055-1
8
4055fb
PIN FUNCTIONS
BAT (Pin 2): Connect to a single-cell Li-Ion battery. Used
as an output when charging the battery and as an input
when supplying power to OUT. When the OUT pin potential
drops below the BAT pin potential, an ideal diode function
connects BAT to OUT and prevents V
OUT
from dropping
more than 100mV below V
BAT
. A precision internal resistor
divider sets the fi nal fl oat potential on this pin. The internal
resistor divider is disconnected when IN1/IN2 and OUT
are in UVLO.
OUT (Pin 3): Voltage Output. Used to provide controlled
power to a USB device from either USB V
BUS
(IN1/IN2) or
the battery (BAT) when the USB is not present. Can also
be used as an input for battery charging when the USB
is not present and a wall adaptor is applied to this pin.
Should be bypassed with at least 10μF to GND.
IN1/IN2 (Pin 4/Pin 1): Input Supply. Connect to USB supply,
V
BUS
. Used as main supply while connected to USB V
BUS
for power control to a USB device. Input current is limited
to either 20% or 100% of the current programmed by the
CLPROG pin as determined by the state of the HPWR pin.
Charge current (to BAT pin) supplied through the inputs is
set to the current programmed by the PROG pin but will
be limited by the input current limit if set greater than the
input current limit.
Connect IN2 to IN1 with a resistance no greater than
0.05Ω.
WALL (Pin 5): Wall Adapter Present Input. Pulling this pin
above 1V will disable charging from IN1/IN2 and disconnect
the power path from IN1/IN2 to OUT. The ACPR pin will
also be pulled low to indicate that a wall adapter has
been detected. Requires the voltage on IN1/IN2 or OUT
to be 100mV greater than V
BAT
and greater than V
UVLO
to
activate this function.
SHDN (Pin 6): Shutdown Input. Pulling this pin greater
than 1.2V will disable the entire part and place it in a low
supply current mode of operation. All power paths will be
disabled. A weak pull-down current is internally applied
to this pin to ensure it is low at power-up when the input
is not being driven externally.
SUSP (Pin 7): Suspend Mode Input. Pulling this pin above
1.2V will disable charging from IN1/IN2 and disconnect
the power path from IN1/IN2 to OUT. The supply current
will be reduced to comply with the USB specifi cation for
Suspend mode. The BAT to OUT ideal diode function will
remain active as well as the ability to charge the battery
from OUT. Suspend mode will reset the charge timer if
V
OUT
is less than V
BAT
while in suspend mode. If V
OUT
is
kept greater than V
BAT
, such as when a wall adapter is
present, the charge timer will not be reset when the part
is put in suspend. A weak pull-down current is internally
applied to this pin to ensure it is low at power-up when
the input is not being driven externally.
HPWR (Pin 8): High Power Select. Used to control the
amount of current drawn from the USB port. A voltage
greater than 1.2V on the pin will set the current limit to
100% of the current programmed by the CLPROG pin
and 100% of the charge current programmed by the
PROG pin. A voltage less than 0.4V on the pin will set
the current limit to 20% of the current programmed by
the CLPROG pin and decrease battery charge current to
16% of the current programmed by the CLPROG pin. A
weak pull-down current is internally applied to this pin to
ensure it is low at power-up when the input is not being
driven externally.
CLPROG (Pin 9): Current Limit Program. Connecting
a resistor, R
CLPROG
to ground, programs the input to
output current limit. The current limit is programmed as
follows:
IA
V
R
V
R
CL
CLPROG
CLPROG CLPROG
() • ,
,
==49 000
49 000
In USB applications the resistor R
CLPROG
should be set
to no less than 105k.
GND (Pin 10): Ground.
PROG (Pin 11): Charge Current Program. Connecting a
resistor, R
PROG
, to ground programs the battery charge
current. The battery charge current is programmed as
follows:
IA
V
R
V
R
CHG
PROG
PROG PROG
() • ,
,
==48 500
48 500
