Datasheet
21
LTC4011
4011fa
APPLICATIO S I FOR ATIO
WUUU
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
that programs the correct number of series cells when it
is connected to the charger, along with indicating chem-
istry and providing temperature information.
Any of these battery pack charge control concepts could
be combined in a variety of ways to service custom
application needs.
PCB Layout Considerations
To prevent magnetic and electrical field radiation and high
frequency resonant problems, proper layout of the com-
ponents connected to the LTC4011 is essential. Refer to
Figure 13. For maximum efficiency, the switch node rise
and fall times should be minimized. The following PCB
design priority list will help ensure proper topology. Lay-
out the PCB using this specific order.
1. Input capacitors should be placed as close as possible
to switching FET supply and ground connections with
the shortest copper traces possible. The switching
Figure 11. NiCd Battery Pack with Time Limit Control
Figure 10. Charging Waveforms Example
7
1200mAhr
NiCd CELLS
BATTERY
PACK
V
TEMP
4
CHEM
10
TIMER
NC
66.5k
4011 F11
+
–
10k
NTC
Figure 12. NiMH Battery Pack Indicating Number of Cells
7
1500mAhr
NiMH CELLS
BATTERY
PACK
V
TEMP
8
V
CELL
R2
4
CHEM
4011 F12
+
–
10k
NTC