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bq27441 Data Memory Parameter Descriptions
6.4.4.2
CC Cal Subclass
6.4.4.2.1 Coulomb Counter Sense Resistor (CC) Offset, Gain, Delta
Subclass
Subclass
Offset
Type
Name
Value
Unit
ID
Min
Max
Default
CC Cal
105
0
I2
CC Offset
–32768
32767
0
Counts
4
F4
CC Gain
1.00E–01
4.00E+01
0.672785
Num
8
F4
CC Delta
3.00E+04
3.00E+06
799341.14
Num
CC Offset
,
CC Gain
, and
CC Delta
are internal calibration parameters that require no customer changes
and are provided for debug purposes only.
Two offsets are used for calibrating the offset of the internal coulomb counter, board layout, sense
resistor, copper traces, and other offsets from the coulomb counter readings.
CC Offset
is the calibration
value that primarily corrects for the offset error of the fuel gauge coulomb counter circuitry. The other
offset calibration is
Board Offset
and is described separately.
CC Offset
is a correction for small noise or
errors; therefore, to maximize accuracy, it takes about 16 seconds to calibrate the offset. Because it is
impractical to do 16-second offset during IC production, the fuel gauge will periodically perform an
CC
Offset
automatic calibration in SLEEP mode. During the automatic calibration, the fuel gauge will set the
CONTROL_STATUS [CCA]
bit.
CC Gain
is the gain factor for calibrating sense resistor, trace, and internal coulomb counter errors. It is
used in the algorithm that reports
AverageCurrent()
.
CC Delta
is a fixed constant based on
CC Gain
used
to cancel out the time base error.
6.4.4.2.2 CC Cal Temp
Subclass
Subclass
Offset
Type
Name
Value
Unit
ID
Min
Max
Default
CC Cal
105
2
I2
CC Cal Temp
0
32767
2982
0.1°K
CC Cal Temp
is the temperature at the time of current calibration. It is also used for RDL temperature
compensation.
6.4.4.3
Current Subclass
6.4.4.3.1 Deadband
Subclass
Subclass
Offset
Type
Name
Value
Unit
ID
Min
Max
Default
Current
107
1
U1
Deadband
0
255
5
mA
The
Deadband
creates a filter window to the reported
AverageCurrent()
register where the current is
reported as 0. Any negative current above this value or any positive current below this value is displayed
as 0.
Only a few reasons may require changing the default value:
1. If the PCB layout has issues that cause inconsistent board offsets from board to board.
2. An extra noisy environment.
50
Data Memory
SLUUAC9A – December 2013 – Revised May 2015
Copyright © 2013–2015, Texas Instruments Incorporated