LTC4110EUHF LINER [Linear Technology], LTC4110EUHF Datasheet - Page 40

• Manufacturer Part Number: LTC4110EUHF
• Description: Battery Backup System Manager
• Manufacturer: LINER [Linear Technology]

LTC4110
APPLICATIONS INFORMATION
where
V
V
V
The resistor divider connected to V
See the Programming Charge Time with TIMER and V
Pins section for more details.
PROGRAMMING CHARGE TIME WITH TIMER AND
V
Charge time limits for Li-Ion batteries can be programmed
by selection of capacitance on the TIMER pin, but is
dependent upon resistance on the V
grammed bulk charge times range from 2 to 12 hours
and is set as follows:
As an example if R
time limit is fi ve hours then C
which directly affects the 944 constant in the Electrical
Characteristics Table for the tolerance.
Avoid capacitors with high leakage currents. The V
pin load resistor range is 49k to 125k or 10μA to 25μA of
load current. At 125k the maximum capacitance on V
is limited to a maximum of 50pF to maintain suffi cient AC
stability for the internal amplifi er. At 49k the maximum is
125pF . The maximum capacitance is inversely proportional
to the resistance.
The voltage (V
precision voltage for other uses with some limitations.
The total V
capacitance must be limited as discussed above. Load
current fl uctuations will modulate the programmed charge
time. In shutdown mode V
In some applications a divided down V
to program the SELA, SELC, TYPE, V
pins. This is easily implemented by use of a resistor divider
connected from V
instead of a single resistor.
40
CUTOFF
CAL
BGR
REF
C
/V
TIMER
PINS
=1.220V
DIS
= adjusted cutoff threshold voltage
= voltage on V
REF
(F) =
pin current must not exceed 25μA and the
REF
(944 • R
REF
VREF
) on the V
to GND that sets the V
T(Hrs)
= 113k and the desired bulk charge
CAL
VREF
REF
or V
REF
(Ω))
will drop to 0V.
TIMER
DIS
pin can be used as a
REF
REF
REF
pin
CHG
pin will affect timer.
= 47nF . See F
voltage is needed
pin. Typical pro-
, V
REF
CAL
pin current
and V
TMR
REF
REF
REF
DIS
If the TYPE pin is set for SLA/LEAD ACID or any nickel
based smart battery, the TIMER pin is not used. You can
ground the TIMER pin. Furthermore, if there is no need
of any timer function and there is no need of any voltage
divider from V
the V
you place a 49.9k load resistor from V
CHARGING BATTERIES OVER 12 HOURS
In situations where required bulk charge time cycle will
exceed the 12 hour time limit imposed by the charge TIMER
pin, you have two options. You can have an SMBus host
clear the CHG_FLT bit and force start another charge cycle
or you can switch to a smart version of the same battery.
If you chose the former, reduce the TIMER pin time to
about 2/3 of the actual time required. This will result in
faster termination in the second cycle and with autorestart
cycles when V
tery option, the smart battery itself safely controls charge
termination. Bulk charge can last as long as necessary
to charge the battery to 100%. No host is required to do
anything, as the battery will maintain its full charge state
using its SMBus charge commands.
PROGRAMMING AC PRESENT INDICATION DELAY
TIME WITH ACPDLY AND V
When the main supply, DCIN, returns after a power failure
the ACPb pin is driven low to indicate presence of main
power. This transition can be delayed to allow time for the
system to stabilize before actions are taken by the system
based on this pin status. The high to low transition only
delay on the ACPb pin can be programmed by selection
of capacitance on the ACPDLY pin, but is dependent upon
resistance on the V
range from 10ms to 200ms and is set as follows:
As an example if R
is 105ms then C
Characteristics Table for the tolerance.
C
ACPDLY
REF
pin between 10μA and 25μA. It is recommended
(F) =
REF
AR
TIMER
is tripped. If you choose the smart bat-
to ground, you must still keep a load on
REF
2 • R
VREF
pin. Typical programmed delay times
T(s)
VREF
= 113k and the desired delay time
= 470nF . See t
REF
(Ω)
PINS
AC
REF
in the Electrical
to ground.
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