LTC4011 Linear Technology, LTC4011 Datasheet - Page 20

• Manufacturer Part Number: LTC4011
• Description: High Efficiency Standalone Nickel Battery Charger
• Manufacturer: Linear Technology

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APPLICATIO S I FOR ATIO
LTC4011
shutdown when the DC adapter is removed, minimizing
current draw from the battery in the absence of an input
power source.
While not a part of the sample waveforms of Figure 10,
temperature qualification is an ongoing part of the charg-
ing process, if an external thermistor network is detected
by the LTC4011. Should prescribed temperature limits be
exceeded during any particular charging state, charging
would be suspended until the sensed temperature re-
turned to an acceptable range.
Battery-Controlled Charging
Because of the programming arrangement of the LTC4011,
it may be possible to configure it for battery-controlled
charging. In this case, the battery pack is designed to pro-
vide customized information to an LTC4011-based charger,
allowing a single design to service a wide range of appli-
cation batteries. Assume the charger is designed to pro-
vide a maximum charge current of 800mA (R
125mΩ). Figure 11 shows a 5V NiCd battery pack for which
20
4
(PAUSE)
U
READY
SHDN
TGATE
V
V
CHRG
V
DCIN
TEMP
CELL
CDIV
TOC
U
V
CC
= 4.25V
PRECHARGE
W
0.9V
Figure 10. Charging Waveforms Example
U
SENSE
FAST CHARGE
200mV
=
EXTERNAL
PAUSE
800mA represents a 0.75C rate. When connected to the
charger, this pack would provide battery temperature in-
formation and correctly configure both fast charge termi-
nation parameters and time limits for the internal NiCd cells.
A second possibility is to configure an LTC4011-based
charger to accept battery packs with varying numbers of
cells. By including R2 of the average cell voltage divider
network shown in Figure 3, battery-based programming
of the number of series-stacked cells could be realized
without defeating LTC4011 detection of battery insertion
or removal. Figure 12 shows a 2-cell NiMH battery pack
Figure 11. NiCd Battery Pack with Time Limit Control
TOP-OFF
TIMER
10
66.5k
CHEM
NC
4
RECHARGE
AUTO
V
TEMP
7
10k
NTC
4011 F10
+
–
SHDN
1200mAhr
NiCd CELLS
BATTERY
PACK
4011 F11
4011p