LTC1730EGN-4 Linear Technology, LTC1730EGN-4 Datasheet - Page 7

• Manufacturer Part Number: LTC1730EGN-4
• Description: IC BATT PULSE CHRGR LI-ION16SSOP
• Manufacturer: Linear Technology

Specifications of LTC1730EGN-4

• Function: Charge Management
• Battery Type: Lithium-Ion (Li-Ion)
• Voltage - Supply: 4.5 V ~ 12 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 16-SSOP (0.150", 3.90mm Width)
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

OPERATIO
The LTC1730 is a complete lithium-ion battery pulse
charger with an internal 0.35 N-MOSFET switch driven
by an internal charge pump. The charge current is set by
the current limit of the input supply (wall adapter). An
external R
current (I
with the wrong current limit from damaging the battery. If
the current limit of the input supply is above I
charging will be immediately terminated and will retry after
400ms (C
while in fast charge mode, the N-channel MOSFET turns
off when the voltage at the BAT pin rises above 4.7V, and
turns back on when the voltage drops below the float
voltage.
A charge cycle begins when the voltage at the V
above the BAT pin by 40mV and the voltage at the NTC/
SHDN pin is in between 0.5 • V
charger will go into trickle charge mode if the battery
voltage is below 2.45V. The trickle charge current is preset
to 35mA and is provided by an internal current source. In
trickle mode, the charge pump and pass transistor are off.
When the battery voltage exceeds 2.45V, the charger goes
into the fast charge mode. In this mode, the charge pump
turns on and ramps up the gate voltage of the pass
transistor turning it on. The voltage at the V
ramps down to V
transistor and R
tion in the pass transistor. The charge current is deter-
mined by the current limit of the input supply.
MAX
SENSE
TIMER
= 0.1V/R
sets the maximum allowable charge over
SENSE
= 0.1 F). If the battery is disconnected
BAT
U
plus the voltage drop across the pass
, thus reducing the power dissipa-
SENSE
) and prevents a wall adapter
CC
and 0.875 • V
CC
CC
MAX
pin rises
pin then
CC
. The
, the
When the battery voltage reaches the final float voltage,
the pass transistor turns off for 100ms (minimum off-
time). It remains off as long as the battery voltage stays
above the float voltage after the 100ms off-time. After the
minimum off-time, if the battery voltage drops below the
float voltage, the pass transistor turns back on for at least
380ms (minimum on-time). As the battery approaches full
charge, the off-time will get longer and the on-time will
stay at 380ms. The voltage at the BAT pin will be slightly
higher than the final float voltage due to the ESR associ-
ated with the battery pack. This voltage level should not
turn on the overvoltage protection circuitry often located
in the battery pack. When the duty cycle at the GATE pin
drops below 10%, a comparator turns off the N-FET at the
CHRG pin and connects a weak current source (40 A) to
ground to indicate a near end-of-charge (C/10) condition.
The pulse charging will continue until the timer stops.
An external capacitor at the TIMER pin sets the total charge
time, the minimum on- and off-time and the overcurrent
retry period. After a time-out has occurred, the charge
cycle is terminated and the CHRG pin is forced high
impedance. To restart the charge cycle, momentarily pull
the NTC/SHDN pin below 50mV or remove and reapply the
input voltage. After the charging stops, if the battery
voltage drops 150mV below the final float voltage, due to
external loading or internal leakage, a new charge cycle
will automatically begins.
The charger can be shut down by pulling the NTC/SHDN
pin to ground. When the input voltage is not present, the
charger goes into a sleep mode, dropping battery drain
current to less than 1 A.
LTC1730-4/LTC1730-4.2
sn1730 1730fs
7