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LT8491
APPLICATIONS INFORMATION
The arrow in Figure 24 shows the proper disconnect point
if removing the battery from the charger in an in-situ bat-
tery charging application. This disconnect point removes
the load and the battery from the charger and is specified
because the LT8491 is not designed to provide power
directly to a load without the presence of a battery.
HOT-PLUGGING CONSIDERATIONS
When connecting a battery to an LT8491 charger, there
can be significant inrush current due to charge equaliza-
tion between the partially charged battery stack and the
charger output capacitors. To a lesser extent, a similar
effect can occur when connecting an illuminated panel
or powered DC supply to the input. The magnitude of the
inrush current depends on (1) the battery, panel or sup-
ply voltage, (2) ESR of the input or output capacitors, (3)
initial voltage of the capacitors, and (4) cable impedance.
Excessive inrush current can lead to sparking that can
compromise connector integrity and/or voltage overshoot
that can cause electrical overstress on LT8491 pins.
Excessive inrush current can be mitigated by first con-
necting the battery or supply to the charger through a
resistive path, followed quickly by a short-circuit. This
can be accomplished using staggered length pins in a
multi-pin connector. This can also be accomplished using
the optional circuit shown in Figure 34 by first connecting
the (+) and (–) battery remote sense connections, which
allow the charger output capacitors to charge through
resistors R2 and R3. Alternatively, consider the use of a
Hot Swap Controller such as the LT1641, LT4256, etc. to
make a current limited connection.
STATUS INDICATOR PIN
The LT8491 reports charger status through the STATUS
pin. To get visual user feedback this pin can be used to
drive a LED. Table 25 describes the LED behavior of this
pin in relationship to the charger status.
2.0s
0.5s
Figure 25. Example Waveform for STATUS Pin in STAGE 3
70
While the LT8491 is operating, the STATUS pin toggles on
a 2 Sec (typical) interval as shown in Figure 25. The three
pulses shown in Figure 25 represent the charger operation
in Stage 3. The STATUS pin will pull up to turn the LED on
and drive to ground to turn the LED off.
Table 25. Status LED Indicator
CHARGER STATUS
Stage 0
Stage 1
Stage 2 and (Stage 3
Enabled or Timer Limits
Enabled or I
OUT
Above C/5)
Stage 2 and (Stage 3
Disabled and Timer Limits
Disabled and I
Below C/10)
Stage 3
Done Charging
CTRL_CHRG_EN = 0
Battery Disconnect Fault
Invalid Battery
Temperature Fault
Timer Expiration Fault
Battery Undervoltage Fault
LITHIUM-ION BATTERY CHARGING
The LT8491 is well suited to charge lithium-ion batter-
ies. Table 26 shows a sample configuration that puts the
LT8491 into a typical setup for lithium-ion battery charging.
8491 F25
For more information
www.analog.com
STATUS LED
PULSES/2.0s,
APPROXIMATE
ON-TIME PER PULSE
1, 10ms
1, 250ms
2, 250ms
Rising
ON
Falling
OUT
3, 250ms
ON
OFF
OFF
OFF
OFF
OFF
FOR MORE
INFORMATION SEE
SECTION
Battery Charging
Algorithm
Battery Charging
Algorithm
Battery Charging
Algorithm, Configure
Stage Timeout Limits,
and Configure Misc.
Battery Charging
Algorithm, Configure
Stage Timeout Limits,
and Configure Misc.
Battery Charging
Algorithm
Configure Charge
Termination
Control Other
Functions
HW Config: Battery
Temperature and
Disconnect Sensing
HW Config: Battery
Temperature and
Disconnect Sensing
Configure Stage
Timeout Limits
Configure V
for
BAT
Stages 0, 1 and 3
Rev. 0
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