LTC4010CFEPBF LINER [Linear Technology], LTC4010CFEPBF Datasheet - Page 11

• Manufacturer Part Number: LTC4010CFEPBF
• Description: High Efficiency Standalone Nickel Battery Charger
• Manufacturer: LINER [Linear Technology]

operaTion
Charge Termination
Fast charge termination parameters are dependent upon
the battery chemistry selected with the CHEM pin. Volt-
age-based termination (–∆V) is always active after the
initial voltage stabilization period. If an external thermistor
network is present, chemistry-specific limits for ∆T/∆t (rate
of temperature rise) are also used in the termination algo-
rithm. Temperature-based termination, if enabled, becomes
active as soon as the fast charge state is entered.
Successful charge termination requires a charge rate
between C/2 and 2C. Lower rates may not produce the
battery voltage and temperature profile required for charge
termination.
Top-Off Charge State
If NiMH fast charge termination occurs because the
∆T/∆t limit is exceeded after an initial period of t
has expired, the LTC4010 enters the top-off charge state.
Top-off charge is implemented by sourcing one-tenth the
programmed charge current for t
that 100% charge has been delivered to the battery. The
CHRG status output is active during the top-off state. If
NiCd cells have been selected with the CHEM pin, the
LTC4010 never enters the top-off state.
Automatic Recharge State
Once charging is complete, the automatic recharge state
is entered to address the self-discharge characteristics of
nickel chemistry cells. The charge status output is inactive
during automatic recharge, but V
to GND to monitor the average cell voltage. If the V
voltage drops below 1.325V without falling below 350mV,
the charge timer is reset and a new fast charge cycle is
initiated.
The internal termination algorithms of the LTC4010 are
adjusted when a fast charge cycle is initiated from auto-
matic recharge, because the battery should be almost fully
charged. Voltage-based termination is enabled immediately
(Refer to Figure 1)
MAX
CDIV
/3 minutes to ensure
remains switched
MAX
CELL
/12
and the NiMH ∆T/∆t limit is fixed at a battery temperature
rise of 1°C/minute.
Fault State
As discussed previously, the LTC4010 enters the fault state
based on detection of invalid battery voltages during vari-
ous charging phases. The IC also monitors the regulation
of the PWM control loop and will enter the fault state if
this is not within acceptable limits. Once in the fault state,
the battery must be removed or DC input power must be
cycled in order to initiate further charging. In the fault
state, the FAULT output is active, the READY output is
inactive, charging stops and the charge indicator output
is inactive. The V
to allow detection of battery removal.
Note that the LTC4010 also uses the FAULT output to indi-
cate that charging is suspended due to invalid battery or
internal die temperatures. However, the IC does not enter
the fault state in these cases and normal operation will
resume when all temperatures return to acceptable levels.
Refer to the Status Outputs section for more detail.
Insertion and Removal of Batteries
The LTC4010 automatically senses the insertion or removal
of a battery by monitoring the V
this voltage fall below 350mV, the IC considers the bat-
tery to be absent. Removing and then inserting a battery
causes the LTC4010 to initiate a completely new charge
cycle beginning with charge qualification.
External Pause Control
After charging is initiated, the V
pause operation at any time. When the voltage between
V
pauses, fast charge termination algorithms are inhibited
and the PWM outputs are disabled. The status and V
outputs all remain active. Normal function is fully restored
from the previous state when pause ends.
TEMP
and GND drops below 200mV, the charge timer
CDIV
output remains connected to GND
TEMP
CELL
pin voltage. Should
pin may be used to
LTC4010

CDIV
4010fb