LTC4098/LTC4098-1
9
40981fc
OVSENS (Pin 1): Overvoltage Protection Sense Input.
OVSENS should be connected through a 6.04k resistor
to the input power connector and the drain of an external
N-channel MOS pass transistor. When the voltage on this
pin exceeds a preset level, the OVGATE pin will be pulled
to GND to disable the pass transistor and protect down-
stream circuitry. If overvoltage protection is not desired,
connect OVSENS to GND.
OVGATE (Pin 2): Overvoltage Protection Gate Output.
Connect OVGATE to the gate pin of an external N-channel
MOS pass transistor. The source of the transistor should
be connected to V
BUS
and the drain should be connected
to the product’s DC input connector. This pin is connected
to an internal charge pump capable of creating sufficient
overdrive to fully enhance the pass transistor. If an over-
voltage condition is detected, OVGATE is brought rapidly
to GND to prevent damage to downstream circuitry. OV-
GATE works in conjunction with OVSENS to provide this
protection. If overvoltage protection is not desired, leave
OVGATE open.
CLPROG (Pin 3): USB Current Limit Program and Monitor
Pin. A 1% resistor from CLPROG to ground determines
the upper limit of the current drawn from the V
BUS
pin.
A precise fraction of the input current, h
CLPROG
, is sent
to the CLPROG pin when the high side switch is on. The
switching regulator delivers power until the CLPROG
pin reaches 1.188V. Therefore, the current drawn from
V
BUS
will be limited to an amount given by h
CLPROG
and
R
CLPROG
. There are several ratios for h
CLPROG
available,
two of which correspond to the 500mA and 100mA USB
specifications. A multilayer ceramic averaging capacitor
is also required at CLPROG for filtering.
NTCBIAS (Pin 4): NTC Thermistor Bias Output. If NTC
operation is desired, connect a bias resistor between
NTCBIAS and NTC, and an NTC thermistor between NTC
and GND. To disable NTC operation, connect NTC to GND
and leave NTCBIAS open.
NTC (Pin 5): Input to the NTC Thermistor Monitoring
Circuits. The NTC pin connects to a negative temperature
coefficient 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
NTCBIAS to NTC and a thermistor is required from NTC
to ground. If the NTC function is not desired, the NTC pin
should be grounded.
BATSENS (Pin 6): Battery Voltage Sense Input. For proper
operation, this pin must always be connected to BAT. For
best performance, connect BATSENS to BAT physically
close to the Li-Ion cell.
PROG (Pin 7): Charge Current Program and Charge Cur-
rent Monitor Pin. Connecting a 1% resistor from PROG
to ground programs the charge current. If sufficient input
power is available in constant-current mode, this pin servos
to 1V. The voltage on this pin always represents the actual
charge current by using the following formula:
I
BAT
=
V
PROG
R
PROG
•1030
CHRG (Pin 8): Open-Drain Charge Status Output. The
CHRG pin indicates the status of the battery charger. Four
possible states are represented by CHRG: charging, not
charging, unresponsive battery and battery temperature
out of range. CHRG is modulated at 35kHz and switches
between a low and a high duty cycle for easy recognition
by either humans or microprocessors. CHRG requires a
pull-up resistor and/or LED to provide indication.
GND (Pin 9, 21): Exposed Pad and pin must be soldered
to the PCB to provide a low electrical and thermal imped-
ance connection to ground.
IDGATE (Pin 10): Ideal Diode Amplifier Output. This pin
controls the gate of an external P-channel MOSFET transis-
tor used to supplement the internal ideal diode. The source
of the P-channel MOSFET should be connected to V
OUT
and the drain should be connected to BAT.
BAT (Pin 11): 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. The LTC4098 will
charge to a maximum voltage of 4.200V. The LTC4098-1
will charge to a maximum voltage of 4.100V.
PIN FUNCTIONS
