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LT8491
2
I
C REGISTER DESCRIPTIONS
CONFIGURE TEMPERATURE COMPENSATION
Table 19. Summary of Temperature Compensation Configuration Registers
REGISTER NAME
SIZE
CFG_CHRG_MISC
BYTE
CFG_TC3
LONG-WORD
CFG_TC2
LONG-WORD
CFG_TC1
LONG-WORD
Some battery chemistries charge best when the charging voltages are adjusted with battery temperature (T
acid batteries experience a significant change in their ideal charging voltage as temperature changes. The LT8491 can
automatically adjust the V
temperature compensation is enabled in the CFG_CHRG_MISC register. See the HW Config: Battery Temperature and
Disconnect Sensing section for more information about the thermistor connection.
When Stage 2 temperature compensation is enabled (CFG_CHRG_MISC→TC_ENABLE bit=1), the PWM duty cycle of
the FBOW pin is automatically adjusted with temperature. This adjusts V
V
stage voltages listed in the Configure V
BAT
V
is automatically adjusted with temperature as follows:
S2
V
(T
) = V
(25°C) • TFACTOR(T
S2
BAT
S2
V
(T
) = V
(25°C) • TFACTOR(T
S3
BAT
S3
Where:
V
(25°C) = Stage 2 V
S2
V
(25°C) = Stage 3 V
S3
TFACTOR(T
) = (1 + ΔT • TC1 + ΔT
BAT
ΔT = (T
in °C) – 25°C
BAT
Using the default TCx coefficients, listed in the I
58
2
2
I
C REGISTER
I
C BOOT READ
ADDRESS
ADDRESS
0x4D
0xAD
0x4E
0xAE
0x52
0xB2
0x56
0xB6
and V
voltages when a temperature sensing thermistor is coupled to the battery. The
S2
S3
for Stages 0, 1 and 3 section, since they are all percentages of V
BAT
)
BAT
)
BAT
at 25°C (see HW Config: V
BAT
at 25°C (see Configure V
BAT
2
• TC2 + ΔT
2
C Register Map, V
140
V
S2
1.30
1.20
1.10
1.00
0.90
0.80
V
S2
0.70
–40
–30
–20
BATTERY TEMPERATURE (°C)
Figure 10. Default Battery Voltage Temperature Compensation in Stage 2
For more information
DESCRIPTION
Contains bit to enable temperature compensation.
3rd order coefficient for Stage 2 and 3 temperature compensation.
2nd order coefficient for Stage 2 and 3 temperature compensation.
1st order coefficient for Stage 2 and 3 temperature compensation.
as T
S2
in Stage 2 (V
) section)
BAT
S2
for Stages 0, 1, and 3)
BAT
3
• TC3)
and V
S2
OR V
> 123.5% OF V
(25°C)
S3
S2
NOT SUPPORTED
OR V
< 82% OF V
(25°C)
S3
S2
NOT SUPPORTED
–10
0
10
20
30
40
50
60
8491 F10
www.analog.com
changes. This also changes all the
BAT
adjust with T
as shown:
S3
BAT
REF
PAGE
57
59
). Lead-
BAT
.
S2
Rev. 0
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