LTC4160EUDC#PBF Linear Technology, LTC4160EUDC#PBF Datasheet - Page 18

• Manufacturer Part Number: LTC4160EUDC#PBF
• Description: IC, BATT CHRG, Li-Ion, Li-Polymer, 1.2A, QFN20
• Manufacturer: Linear Technology

Specifications of LTC4160EUDC#PBF

• Battery Type: Li-Ion, Li-Polymer
• Input Voltage: 5.5V
• Battery Charge Voltage: 4.2V
• Charge Current Max: 1.2A
• Battery Ic Case Style: QFN
• No. Of Pins: 20
• No. Of Series Cells: 1
• Rohs Compliant: Yes
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

OPERATION
LTC4160/LTC4160-1
the battery will eventually self discharge. To ensure that
the battery is always topped off, a charge cycle will auto-
matically begin when the battery voltage falls below the
recharge threshold which is typically 100mV less than
the charger’s float voltage. In the event that the safety
timer is running when the battery voltage falls below the
recharge threshold, it will reset back to zero. To prevent
brief excursions below the recharge threshold from reset-
ting the safety timer, the battery voltage must be below
the recharge threshold for more than 1ms. The charge
cycle and safety timer will also restart if the V
cycles low and then high (e.g., V
replaced), or if the battery charger is cycled on and off by
the ENCHARGER pin.
Charge Current
The charge current is programmed using a single resis-
tor from PROG to ground. 1/1030th of the battery charge
current is sent to PROG, which will attempt to servo to
1.000V. Thus, the battery charge current will try to reach
1030 times the current in the PROG pin. The program
resistor and the charge current are calculated using the
following equation:
In either the constant-current or constant-voltage charging
modes, the voltage at the PROG pin will be proportional to
the actual charge current delivered to the battery. There-
fore, the actual charge current can be determined at any
time by monitoring the PROG pin voltage and using the
following equation:
In many cases, the actual battery charge current, I
be lower than I
prioritization with the system load drawn from V
The Battery Charger Flow Chart on the next page illustrates
the battery charger’s algorithm.
18
I
I
CHG
BAT
=
=
R
R
V
V
PROG
PROG
PROG
PROG
CHG
•1030
• 1030
due to limited input power available and
BUS
is removed and then
BUS
OUT
BAT
UVLO
.
, will
Charge Status Indication
The CHRG and FAULT pins can be used to indicate the status
of the battery charger. Two possible states are represented
by CHRG: charging and not charging. An open-drain output,
the CHRG pin can drive an indicator LED through a current
limiting resistor for human interfacing or simply a pull-up
resistor for microprocessor interfacing.
When charging begins, CHRG is pulled low and remains
low for the duration of a normal charge cycle. When charg-
ing is complete, i.e., the BAT pin reaches the float and the
charge current has dropped to one tenth of the programmed
value, the CHRG pin goes high. The CHRG pin does not
respond to the C/10 threshold if the LTC4160/LTC4160-1
is in V
charge indications due to insufficient power available to
the battery charger.
Table 2 illustrates the possible states of the CHRG and
FAULT pins when the battery charger is active.
Table 2. Charge Status Readings Using the CHRG and FAULT Pins
An NTC fault pauses charging while the battery tempera-
ture is out of range but is not indicated using the CHRG
or FAULT pins.
If a battery is found to be unresponsive to charging (i.e.,
its voltage remains below 2.85V for 1/2 hour) the CHRG
pin goes high and the FAULT pin goes low to indicate a
bad battery fault.
Note that the LTC4160/LTC4160-1 are 3-terminal
PowerPath products where system load is always priori-
tized over battery charging. Due to excessive system load,
there may not be sufficient power to charge the battery
beyond the trickle charge threshold voltage within the bad
battery timeout period. In this case, the battery charger
will falsely indicate a bad battery. System software may
then reduce the load and reset the battery charger to try
again.
The FAULT pin is also used to indicate whether there is
a short circuit condition on V
Charging/NTC Fault
BUS
Not Charging
Bad Battery
STATUS
input current limit. This prevents false end-of-
CHRG
High
High
Low
BUS
when the bidirectional
FAULT
High
High
Low
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