LTC4090EDJC#PBF Linear Technology, LTC4090EDJC#PBF Datasheet - Page 17

• Manufacturer Part Number: LTC4090EDJC#PBF
• Description: IC USB POWER MANAGER 22-DFN
• Manufacturer: Linear Technology

Specifications of LTC4090EDJC#PBF

• Function: Power Management
• Battery Type: Lithium-Ion (Li-Ion), Lithium-Polymer (Li-Pol)
• Voltage - Supply: 4.35 V ~ 5.5 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 22-WFDFN Exposed Pad
• Supply Voltage Range: 4.35V To 5.5V
• Operating Temperature Range: -40°C To +85°C
• Digital Ic Case Style: DFN
• No. Of Pins: 22
• Msl: MSL 1 - Unlimited
• Termination Type: SMD
• Supply Voltage Min: 4.35V
• Rohs Compliant: Yes
• Filter Terminals: SMD
• Frequency: 2.7MHz
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

OPERATION
For example, if the full charge current is programmed
to 500mA with a 100k PROG resistor the CHRG pin will
change state at a battery charge current of 50mA.
Note: The end-of-charge (EOC) comparator that moni-
tors the charge current latches its decision. Therefore,
the fi rst time the charge current drops below 10% of the
programmed full charge current while in constant-volt-
age mode, it will toggle CHRG to a high impedance state.
If, for some reason the charge current rises back above
the threshold, the CHRG pin will not resume the strong
pull-down state. The EOC latch can be reset by a recharge
cycle (i.e., V
toggling the input power to the part.
Automatic Recharge
After the battery charger terminates, it will remain off
drawing only microamperes of current from the battery. If
the product remains in this state long enough, the battery
will eventually self discharge. To ensure that the battery is
always topped off, a charge cycle will automatically begin
when the battery voltage falls below V
4.1V). To prevent brief excursions below V
resetting the safety timer, the battery voltage must be
below V
charge cycle and safety timer will also restart if the IN
UVLO cycles low and then high (e.g., IN is removed and
then replaced).
Thermal Regulation
To prevent thermal damage to the IC or surrounding
components, an internal thermal feedback loop will
automatically decrease the programmed charge current
if the die temperature rises to approximately 105°C.
Thermal regulation protects the LTC4090/LTC4090-5
from excessive temperature due to high power operation
or high ambient thermal conditions and allows the user
to push the limits of the power handling capability with a
given circuit board design without risk of damaging the
LTC4090/LTC4090-5 or external components. The benefi t
RECHRG
BAT
drops below the recharge threshold) or
for more than a few milliseconds. The
RECHRG
RECHRG
(typically
from
of the LTC4090/LTC4090-5 thermal regulation loop is that
charge current can be set according to actual conditions
rather than worst-case conditions with the assurance that
the battery charger will automatically reduce the current
in worst-case conditions.
Undervoltage Lockout
An internal undervoltage lockout circuit monitors the input
voltage (IN) and the output voltage (OUT) and disables
either the input current limit or the battery charger circuits
or both. The input current limit circuitry is disabled until
V
exceeds V
abled until V
lockout comparators have built-in hysteresis.
NTC Thermistor
The battery temperature is measured by placing a nega-
tive temperature coeffi cient (NTC) thermistor close to
the battery pack. To use this feature connect the NTC
thermistor, R
bias resistor, R
1% resistor with a value equal to the value of the chosen
NTC thermistor at 25°C (denoted R
The LTC4090/LTC4090-5 will pause charging when the
resistance of the NTC thermistor drops to 0.41 times the
value of R
thermistor, this corresponds to approximately 50°C). The
safety timer also pauses until the thermistor indicates a
return to a valid temperature. As the temperature drops,
the resistance of the NTC thermistor rises. The LTC4090/
LTC4090-5 are also designed to pause charging (and timer)
when the value of the NTC thermistor increases to 2.82
times the value of R
this resistance, 28.2k, 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.
IN
rises above the undervoltage lockout threshold and V
OUT
25C
OUT
NTC
by 50mV. The battery charger circuits are dis-
or approximately 4.1k (for a Vishay curve 2
NOM
exceeds V
LTC4090/LTC4090-5
, between the NTC pin and ground and a
, from VNTC to NTC. R
25C
. For a Vishay curve 2 thermistor
BAT
by 50mV. Both undervoltage
25C
).
NOM
should be a
17
4090fc
IN