Hw Config: Battery Temperature And Disconnect Sensing; Hw Config: Shdn Pin Connections; Hw Config: Mode Pin - Current Conduction Mode - Analog Devices LINEAR LT8491 Manual

APPLICATIONS INFORMATION
bias currents of the C
SNOUT
sents a ~0.5% reduction in the maximum current limit
which typically occurs with ~50mV across R
C/10 threshold (typically when 5mV is measured across
C and C ) would also reduce to C/10.5 due to
SPOUT SNOUT
the 0.25mV drop across R
and R will show up in the telemetry as a small error.
S2
HW Config: Battery Temperature and Disconnect
Sensing
The LT8491 can measure the battery temperature using
an NTC (negative temperature coefficient) thermistor
thermally coupled to the battery pack. Connect a 10kΩ,
β = 3380 NTC thermistor from the TEMPSENSE pin to
ground and an 18.2k (1% tolerance or better) resistor
from AV to TEMPSENSE, as shown in Figure 18. If bat-
DD
tery temperature monitoring is not required, then use a
10k resistor in place of the thermistor. This will indicate
to the LT8491 that the battery is always at 25°C.
TO CHARGER OUTPUT
AT R
SENSE2
LT8491
AV
DD
18.2k
TEMPSENSE
GND
Figure 18. Battery Temperature and Disconnect Sensing Circuit
Using the thermally coupled thermistor, the LT8491 can
accurately measure battery temperatures from –40°C to
60°C which can be read from the TELE_TBAT register.
TELE_TBAT will report temperatures between ~ –45°C to
65°C, but with reduced accuracy outside of the –40°C to
60°C range.
The LT8491 can use the battery temperature information to
compensate the battery charging voltages as discussed in
the Configure Temperature Compensation section. High and
low temperature fault limits can also be configured as dis-
cussed in the Configure Temperature Fault Limits section.
and C pins. This repre-
SNIN
SENSE
. The voltage drop across R
S2
CABLE
TO/FROM
CHARGER
100nF
10k NTC THERMISTOR
THERMALLY COUPLED
WITH BATTERY PACK
8491 F18
For more information
The LT8491 detects if the battery has been disconnected
from the charger by monitoring the TEMPSENSE pin
. The voltage. When the connection to the battery is severed,
the connection to the thermistor is also severed and the
TEMPSENSE voltage rises to AV
resistor. A TEMPSENSE voltage greater than 96% of AV
S1
(typical) indicates that the thermistor has been discon-
nected and activates a fault condition. See the Charging
Faults section for details.

HW Config: SHDN Pin Connections

The LT8491 requires more than 1.234V (typical) on the
SHDN pin to start up. A minimum of 5V on V
required for proper start-up operation; therefore, a resis-
tor divider from V
threshold. Connect the SHDN pin as shown in Figure 19
(1% resistor tolerance or better required).
V
IN
Figure 19. SHDN Pin Resistor Divider
HW Config: MODE Pin – Current Conduction Mode
The LT8491 has two modes of switching behavior con-
trolled by the state of the MODE pin. Tying MODE to a volt-
age above 2.3V (i.e., V
for discontinuous conduction mode (DCM) which allows
only positive current flow to the battery. More information
about this mode of operation can be found in the LT8705
data sheet.
Tying the MODE pin below 0.4V (i.e. ground) changes the
switching behavior as follows:
1. Automatic CCM/DCM Mode Switching: Very large
inductor current ripple can lead the LT8491 to operate
with high peak inductor currents while still in DCM. In
this case, the M4 switch (highlighted in Figure 20) can
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through the 18.2k
DD
to the SHDN pin is used to set this
IN
LT8491
V
IN
110k
SHDN
35.7k
GND
8491 F19
or INTV ) configures the part
DD CC
LT8491
DD
is also
IN
Rev. 0
67