LTC4071
6
4071fc
pin FuncTions
NTCBIAS (Pin 1): NTC Bias Pin. Connect a resistor from
NTCBIAS to NTC, and a thermistor from NTC to GND. Float
NTCBIAS when not in use. Minimize parasitic capacitance
on this pin.
NTC (Pin 2): Input to the Negative Temperature Coefficient
Thermistor Monitoring Circuit. The NTC pin connects to
a negative temperature coefficient thermistor which is
typically co-packaged with the battery to determine the
temperature of the battery. If the battery temperature is too
high, the float voltage is reduced. Connect a low drift bias
resistor from NTCBIAS to NTC and a thermistor from NTC
to GND. When not in use, connect NTC to V
CC
. Minimize
parasitic capacitance on this pin.
ADJ (Pin 3): Float Voltage Adjust Pin. Connect ADJ to GND
to program 4.0V float voltage. Disconnect ADJ to program
4.1V float voltage. Connect ADJ to V
CC
to program 4.2V
float voltage. The float voltage is also adjusted by the NTC
thermistor.
HBO (Pin 4): High Battery Monitor Output (Active High).
HBO is a CMOS output that indicates that the battery is
almost fully charged and current is being shunted away
from V
CC
. This pin is driven high when V
CC
rises to within
V
HBTH
of the effective float voltage, V
FLOAT_EFF
. The absolute
value of this threshold depends on ADJ and NTC both of
which affect the float voltage. HBO is driven low when V
CC
falls by more than (V
HBTH
+ V
HBHY
) below the effective
float voltage. Refer to Table 1 for the effective float voltage.
LBSEL (Pin 5): Low Battery Disconnect Select Pin. Con-
nect LBSEL to GND to select a low battery disconnect
level of 3.2V, connect LBSEL to V
CC
to select a low battery
disconnect level of 2.7V. Do not float.
GND (Pin 6, Exposed Pad Pin 9): Ground. The exposed
package pad has no internal electrical connection but must
be connected to PCB ground for maximum heat transfer.
BAT (Pin 7): Battery Pin. Battery charge current is sourced
from V
CC
through this pin when an external supply is
present. BAT supplies current to V
CC
from this pin when
no other source of power is available. If BAT falls below
V
LBD
this pin disconnects the battery from V
CC
protecting
the battery from discharge by the load when no external
power supply is present.
V
CC
(Pin 8): Input Supply Pin. Attach system load to this
pin. The input supply voltage is regulated to 4.0V, 4.1V,
or 4.2V depending on the ADJ pin state (see the ADJ pin
description for more detail). This pin can sink up to 50mA
in order to keep the voltage regulation within accuracy
limits. Decouple to GND with a capacitor, C
IN
, of at least
0.1µF, use a larger decoupling cap to handle high peak
load currents.
