LTC4060
U
OPERATIO
appliedtotheSHDNpin, shutdownendsandchargequali-
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.
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.
Precharge
When VCELL (VBAT/Number of Cells) is below 2.05V (VBR),
a battery is assumed to be present. Should VCELL rise
above 1.95V (VBOV) 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 VCELL has fallen below 1.9V
(VBOV –VBOVH)onlybyremovingandreplacingthebattery
(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.
The state that is entered when qualified charging begins is
precharge. TheCHRGstatusoutputissetlowandremains
low during both precharge and fast charge. If the voltage
on VCELL is below the 900mV (VFCQ) fast charge qualifica-
tion voltage, the LTC4060 charges using one-fifth the
maximumprogrammedchargecurrent. Thecellvoltageis
continuously checked to determine when the battery is
ready to accept a fast charge. Until this voltage reaches
VFCQ, 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.
If the NTC pin voltage is above the temperature disable
threshold (VNDIS), 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 VCC
drops below the undervoltage lockout threshold, sleep
mode is entered.
Fast Charge
WhentheaveragecellvoltageexceedsVFCQ, theLTC4060
transitionsfromtheprechargetothefastchargestateand
Table 1. LTC4060 Time Limit Programming Examples
TYPICAL
FAST
CHARGE
RATE
BATTERY
VOLTAGE
STABILIZATION
HOLD OFF
CHARGE
TIME
LIMIT
BATTERY AUTOMATIC
VOLTAGE
SAMPLING
INTERVAL
RECHARGE
ENTRY
DELAY
UVLO EXIT, BATTERY
INSERTION/REMOVAL/OVERVOLTAGE,
FAST CHARGE ENTRY AND
FAST
CHARGE
CURRENT
(t
MAX
)
R
PROG
C
TIMER
(C)
(MINUTES)
(HOURS) (SECONDS) (SECONDS)
THERMISTOR EVENT DELAYS (ms)
2A
2A
698Ω
698Ω
1nF
1.5
1
4.6 to 5.7
6.9 to 8.4
8.4 to 10.3
12.6 to 15.4
4.2 to 5.2
6.3 to 7.7
8.9 to 11
1.1
1.6
2
15
23
28
42
14
21
30
42
15 to 31
23 to 46
28 to 56
42 to 84
14 to 28
21 to 42
30 to 60
42 to 84
175 to 260
260 to 390
320 to 480
480 to 720
160 to 240
240 to 360
340 to 510
480 to 720
1.5nF
1.8nF
2.7nF
180pF
270pF
390pF
560pF
2A
698Ω
0.75
0.5
1.5
1
2A
698Ω
3
400mA
400mA
400mA
400mA
3480Ω
3480Ω
3480Ω
3480Ω
1
1.5
2.1
3
0.75
0.5
12.6 to 15.4
4060f
10
Linear Systems [ Linear Systems ]
