LTC4097EDDB#PBF Linear Technology, LTC4097EDDB#PBF Datasheet - Page 13

• Manufacturer Part Number: LTC4097EDDB#PBF
• Manufacturer: Linear Technology
• Type: Battery Chargerr

Specifications of LTC4097EDDB#PBF

• Battery Type: Li-Ion/Li-Pol
• Output Voltage: 4.2V
• Operating Supply Voltage (min): 4.25V
• Operating Supply Voltage (max): 5.5V
• Operating Temp Range: -40C to 85C
• Mounting: Surface Mount
• Pin Count: 12
• Operating Temperature Classification: Industrial
• Lead Free Status / RoHS Status: Compliant

Manual Shutdown
The SUSP pin has a 3.4MΩ pulldown resistor to GND. A
logic low enables the charger and a logic high disables it
(the pulldown defaults the charger to the charging state).
The DCIN input draws 20µA when the charger is in shut-
down. The USBIN input draws 20µA during shutdown if
no power is applied to DCIN, but draws only 10µA when
V
NTC Thermistor
The battery temperature is measured by placing a nega-
tive temperature coeffi cient (NTC) thermistor close to
the battery pack. The NTC circuitry is shown in the Block
Diagram of Figure 4. To use this feature, connect the NTC
thermistor, R
bias resistor, R
a 1% resistor with a value equal to the value of the chosen
NTC thermistor at 25°C (R25).
The LTC4097 will pause charging when the resistance of
the 100k NTC thermistor drops to 0.54 times the value of
R25 or approximately 54k (for a Vishay “Curve 1” therm-
istor, this corresponds to approximately 40°C). As the
temperature drops, the resistance of the NTC thermistor
OPERATION
DCIN
> V
USBIN
NTC
.
NOM
, between the NTC pin and ground and a
, from VNTC to NTC. R
NOM
should be
rises. The LTC4097 is also designed to pause charging
when the value of the NTC thermistor increases to 3.25
times the value of R25. For a Vishay “Curve 1” thermistor
this resistance, 325k, corresponds to approximately 0°C.
The hot and cold comparators each have approximately
3°C of hysteresis to prevent oscillation about the trip point.
Grounding the NTC pin disables all NTC functionality.
Thermal Limiting
An internal thermal feedback loop reduces the programmed
charge current if the die temperature attempts to rise
above a preset value of approximately 115°C. This feature
protects the LTC4097 from excessive temperature and
allows the user to push the limits of the power handling
capability of a given circuit board without risk of damag-
ing the device. The charge current can be set according
to typical (not worst case) ambient temperature with the
assurance that the charger will automatically reduce the
current in worst case conditions. A safety thermal shut
down circuit will turn off the charger if the die temperature
rises above a value of approximately 150°C. DFN power
considerations are discussed further in the Applications
Information section.
LTC4097
13
4097f