BQ2014_15 Datasheet, PDF (13/27 Pages) Texas Instruments – Gas Gauge IC with External Charge Control

Not Recommended For New Designs
bq2014
Temperature and Gas Gauge Register
(TMPGG)
The read-only TMPGG register (address=02h) contains
two data fields. The first field contains the battery tem-
perature. The second field contains the available charge
from the battery.
TMPGG Temperature Bits
7
6
5
4
3210
TMP3 TMP2 TMP1 TMP0 - - -
The bq2014 contains an internal temperature sensor.
The temperature is used to set charge and discharge ef-
ficiency factors as well as to adjust the self-discharge co-
efficient. The temperature register contents may be
translated as shown in Table 7.
The bq2014 calculates the available charge as a function
of NAC, temperature, and LMD. The results of the cal-
culation are available via the display port or the gas
gauge field of the TMPGG register. The register is used
to
give
available
capacity
in
1
16
increments
from
0
to
1516_.
TMPGG Gas Gauge Bits
7 65 4
3
2
1
0
-
--
- GG3 GG2 GG1 GG0
Table 7. Temperature Register Translation
TMP3
0
0
0
0
0
0
0
0
1
1
1
1
1
TMP2
0
0
0
0
1
1
1
1
0
0
0
0
1
TMP1
0
0
1
1
0
0
1
1
0
0
1
1
0
TMP0
0
1
0
1
0
1
0
1
0
1
0
1
0
Temperature
T < -30°C
-30°C < T < -20°C
-20°C < T < -10°C
-10°C < T < 0°C
0°C < T < 10°C
10°C < T < 20°C
20°C < T < 30°C
30°C < T < 40°C
40°C < T < 50°C
50°C < T < 60°C
60°C < T < 70°C
70°C < T < 80°C
T > 80°C
On reset, NACH and NACL are cleared to 0. When the
bq2014 detects a charge, NACL resets to 0. NACH and
NACL are reset to 0 on the first valid charge after VSB =
EDV1. Writing to the NAC registers affects the available
charge counts and, therefore, affects the bq2014 gas
gauge operation. Do not write the NAC registers to a
value greater than LMD.
The gas gauge display and the gas gauge portion of the
TMPGG register are adjusted for cold temperature de-
pendencies. A piece-wise correction is performed as fol-
lows:
Temperature
> 0°C
Available Capacity Calculation
NAC / “Full Reference”
-20°C < T < 0°C
< -20°C
0.75 _* NAC / “Full Reference”
0.5 _* NAC / “Full Reference”
The adjustment between > 0°C and -20°C < T < 0°C has a
10°C hysteresis.
Nominal Available Charge Register
(NACH/NACL)
The read/write NACH register (address=03h) and the
read-only NACL low-byte register (address=17h) are the
main gas gauging registers for the bq2014. The NAC
registers are incremented during charge actions and
decremented during discharge and self-discharge ac-
tions. The correction factors for charge/discharge effi-
ciency are applied automatically to NAC.
Battery Identification Register (BATID)
The read/write BATID register (address=04h) is avail-
able for use by the system to determine the type of bat-
tery pack. The BATID contents are retained as long as
VCC is greater than 2V. The contents of BATID have no
effect on the operation of the bq2014. There is no de-
fault setting for this register.
Last Measured Discharge Register (LMD)
LMD is a read/write register (address=05h) that the
bq2014 uses as a measured full reference. The bq2014
adjusts LMD based on the measured discharge capacity
of the battery from full to empty. In this way the bq2014
updates the capacity of the battery. LMD is set to PFC
during a bq2014 reset.
Secondary Status Flags Register (FLGS2)
The read-only FLGS2 register (address=06h) contains
the secondary bq2014 flags.
The charge rate flag (CR) is used to denote the fast
charge regime. Fast charge is assumed whenever a
charge action is initiated. The CR flag remains asserted
if the charge rate does not fall below 2 counts/sec.
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