LTC4060 Linear Integrated, LTC4060 Datasheet - Page 10

• Manufacturer Part Number: LTC4060
• Description: Standalone Linear NiMH/NiCd Fast Battery Charger
• Manufacturer: Linear Integrated

OPERATIO
LTC4060
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
a battery is assumed to be present. Should V
above 1.95V (V
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
(V
(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
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
drops below the undervoltage lockout threshold, sleep
mode is entered.
Table 1. LTC4060 Time Limit Programming Examples
10
CURRENT
CHARGE
BOV
400mA
400mA
400mA
400mA
FAST
2A
2A
2A
2A
– V
CELL
BOVH
(V
NDIS
3480Ω
3480Ω
3480Ω
3480Ω
R
698Ω
698Ω
698Ω
698Ω
) only by removing and replacing the battery
PROG
BAT
BOV
), the LTC4060 verifies that the ther-
U
/Number of Cells) is below 2.05V (V
) for a time greater than the battery
C
180pF
270pF
390pF
560pF
1.5nF
1.8nF
2.7nF
TIMER
1nF
CELL
TYPICAL
CHARGE
FAST
RATE
0.75
0.75
(C)
1.5
0.5
1.5
0.5
1
1
has fallen below 1.9V
STABILIZATION
12.6 to 15.4
12.6 to 15.4
(MINUTES)
8.4 to 10.3
HOLD OFF
VOLTAGE
BATTERY
4.6 to 5.7
6.9 to 8.4
4.2 to 5.2
6.3 to 7.7
8.9 to 11
CELL
BR
rise
CC
(HOURS)
CHARGE
),
LIMIT
(t
TIME
MAX
1.1
1.6
1.5
2.1
2
3
1
3
)
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
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
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
transitions from the precharge to the fast charge state and
FCQ
(SECONDS)
SAMPLING
INTERVAL
VOLTAGE
BATTERY
CELL
, the LTC4060 remains in precharge.
15
23
28
42
14
21
30
42
is below the 900mV (V
AUTOMATIC
(SECONDS)
RECHARGE
15 to 31
23 to 46
28 to 56
42 to 84
14 to 28
21 to 42
30 to 60
42 to 84
ENTRY
DELAY
INSERTION/REMOVAL/OVERVOLTAGE,
THERMISTOR EVENT DELAYS (ms)
FAST CHARGE ENTRY AND
FCQ
UVLO EXIT, BATTERY
) fast charge qualifica-
175 to 260
260 to 390
320 to 480
480 to 720
160 to 240
240 to 360
340 to 510
480 to 720
FCQ
, the LTC4060
4060f