Datasheet

10
LTC4060
4060f
Table 1. LTC4060 Time Limit Programming Examples
TYPICAL BATTERY CHARGE BATTERY AUTOMATIC
FAST VOLTAGE TIME VOLTAGE RECHARGE UVLO EXIT, BATTERY
FAST CHARGE STABILIZATION LIMIT SAMPLING ENTRY INSERTION/REMOVAL/OVERVOLTAGE,
CHARGE RATE HOLD OFF (t
MAX
) INTERVAL DELAY FAST CHARGE ENTRY AND
CURRENT R
PROG
C
TIMER
(C) (MINUTES) (HOURS) (SECONDS) (SECONDS) THERMISTOR EVENT DELAYS (ms)
2A 698Ω 1nF 1.5 4.6 to 5.7 1.1 15 15 to 31 175 to 260
2A 698Ω 1.5nF 1 6.9 to 8.4 1.6 23 23 to 46 260 to 390
2A 698Ω 1.8nF 0.75 8.4 to 10.3 2 28 28 to 56 320 to 480
2A 698Ω 2.7nF 0.5 12.6 to 15.4 3 42 42 to 84 480 to 720
400mA 3480Ω 180pF 1.5 4.2 to 5.2 1 14 14 to 28 160 to 240
400mA 3480Ω 270pF 1 6.3 to 7.7 1.5 21 21 to 42 240 to 360
400mA 3480Ω 390pF 0.75 8.9 to 11 2.1 30 30 to 60 340 to 510
400mA 3480Ω 560pF 0.5 12.6 to 15.4 3 42 42 to 84 480 to 720
OPERATIO
U
applied to the SHDN pin, shutdown ends and charge quali-
fication is entered.
Charge Qualification
After exiting the sleep or shutdown modes the LTC4060
will check for the presence of a battery and for proper
battery temperature (if a thermistor is used) before initiat-
ing charging.
When V
CELL
(V
BAT
/Number of Cells) is below 2.05V (V
BR
),
a battery is assumed to be present. Should V
CELL
rise
above 1.95V (V
BOV
) for a time greater than the battery
overvoltage event delay shown in the far right column of
Table 1, then a battery overvoltage condition is detected
and charging stops. Once stopped in this way, qualifica-
tion can be reinitiated after V
CELL
has fallen below 1.9V
(V
BOV
– V
BOVH
) only by removing and replacing the battery
(or replacing the battery if the overvoltage condition is a
result of battery removal), toggling the SHDN pin low to
high or removing and reapplying power to the charger.
If the NTC pin voltage is above the temperature disable
threshold (V
NDIS
), the LTC4060 verifies that the ther-
mistor temperature is between 5°C and 45°C. Charging
will not initiate until these temperature limits are met.
The LTC4060 continues to qualify important voltage and
temperature parameters during all charging states. If V
CC
drops below the undervoltage lockout threshold, sleep
mode is entered.
If the internal die temperature becomes excessive, charg-
ing stops and the part enters the shutdown state. Once in
the shutdown state charge qualification can be reinitiated
only when the die temperature drops to normal and then
by removing and replacing the battery or toggling the
SHDN pin low to high or removing and reapplying power
to the charger.
Precharge
The state that is entered when qualified charging begins is
precharge. The CHRG status output is set low and remains
low during both precharge and fast charge. If the voltage
on V
CELL
is below the 900mV (V
FCQ
) fast charge qualifica-
tion voltage, the LTC4060 charges using one-fifth the
maximum programmed charge current. The cell voltage is
continuously checked to determine when the battery is
ready to accept a fast charge. Until this voltage reaches
V
FCQ
, the LTC4060 remains in precharge.
If an external thermistor indicates that the sensed tem-
perature is beyond a range of 5°C to 45°C charging is
suspended, the charge timer is paused and the CHRG
status output remains low. Normal charging resumes
from the previous state when the sensed temperature
rises above 5°C or falls below 45°C.
Fast Charge
When the average cell voltage exceeds V
FCQ
, the LTC4060
transitions from the precharge to the fast charge state and