LTC4089-1
8
40891fa
GND (Pins 1, 2): Ground. Tie the GND pin to a local ground
plane below the LTC4089-1 and the circuit components.
HVOUT (Pins 3, 18): Voltage Output of the High Voltage
Regulator. When suffi cient voltage is present at HVOUT, the
low voltage power path from IN to OUT will be disconnected
and the HVPR pin will be pulled low to indicate that a high
voltage wall adapter has been detected. The LTC4089-1
high voltage regulator will provide a fi xed 5V output to
the battery charger MOSFET. HVOUT should be bypassed
with at least 10μF to GND. Connect pins 3 and 18 with a
resistance no greater than 1Ω.
V
C
(Pin 4): Leave the V
C
pin fl oating or bypass to ground
with a 10pF capacitor. This optional 10pF capacitor reduces
HVOUT ripple in discontinuous mode.
NTC (Pin 5): Input to the NTC Thermistor Monitoring
Circuits. The NTC pin connects to a negative temperature
coeffcient thermistor which is typically co-packaged with
the battery pack to determine if the battery is too hot or
too cold to charge. If the battery’s temperature is out of
range, charging is paused until the battery temperature re-
enters the valid range. A low drift bias resistor is required
from V
NTC
to NTC and a thermistor is required from NTC
to ground. If the NTC function is not desired, the NTC pin
should be grounded.
VNTC (Pin 6): Output Bias Voltage for NTC. A resistor from
this pin to the NTC pin will bias the NTC thermistor.
HVPR (Pin 7): High Voltage Present Output. Active low
open drain output pin. A low on this pin indicates that the
high voltage regulator has suffi cient voltage to charge the
battery. This feature is disabled if no power is present on
HVIN, IN or BAT (i.e., below UVLO thresholds).
CHRG (Pin 8): Open-Drain Charge Status Output. When the
battery is being charged, the CHRG pin is pulled low by an
internal N-channel MOSFET. When the timer runs out or
the charge current drops below 10% of the programmed
charge current or the input supply is removed, the CHRG
pin is forced to a high impedance state.
PROG (Pin 9): 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
CHG
PROG
()
,
=
50 000
GATE (Pin 10): External ideal diode gate pin. This pin can
be used to drive the gate of an optional external PFET
connected between BAT (drain) and OUT (source). By doing
so, the impedance of the ideal diode between BAT and OUT
can be reduced. When not in use, this pin should be left
fl oating. It is important to maintain a high impedance on
this pin and minimize all leakage paths.
BAT (Pin 11): Connect to a single cell Li-Ion battery. This
pin is 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 (charging) potential on
this pin. The internal resistor divider is disconnected when
IN and HVIN are in undervoltage lockout.
IN (Pin 12): Input Supply. Connect to USB supply, V
BUS
.
Input current to this pin 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 the BAT pin) supplied through the input is set to the
current programmed by the PROG pin but will be limited
by the input current limit if charge current is set greater
than the input current limit.
OUT (Pin 13): Voltage Output. This pin is used to provide
controlled power to a USB device from either USB V
BUS
(IN), an external high voltage supply (HVIN), or the battery
(BAT) when no other supply is present. The high voltage
supply is prioritized over the USB V
BUS
input. OUT should
be bypassed with at least 4.7μF to GND.
PIN FUNCTIONS
