BQ2014H Datasheet, PDF (13/22 Pages) Texas Instruments – Low-Cost NiCd/NiMH Gas Gauge IC

Preliminary bq2014H
The capacity inaccurate flag (CI) is used to warn the
user that the battery has been charged a substantial
number of times since LMD has been updated. The CI
flag is asserted on the 64th charge after the last LMD
update or when the bq2014H is reset. The flag is cleared
after an LMD update.
The CI values are
FLGS1 Bits
7
65
4
3
2
1
0
-
- - CI -
-
-
-
where CI is
0 When LMD is updated with a valid full dis-
charge
1 After the 64th valid charge action with no
LMD updates or the bq2014H is reset
The valid discharge flag (VDQ) is asserted when the
bq2014H is discharged from NAC = 0.94 ∗ LMD. The
flag remains set until either LMD is updated or one of
three actions that can clear VDQ occurs:
I When NAC has been reduced by more than 6.25%
because of self-discharge since VDQ was set.
I A valid charge action is sustained at V_SRO > V_SRQ
for at least 2 NAC updates.
I The EDV1 flag was set at a temperature below 0°C
The VDQ values are
FLGS1 Bits
7
65
4
3
2
1
0
-
--
- VDQ -
-
-
where VDQ is
0 Self-discharge of more than 6.25% of NAC,
valid charge action detected, EDV1 asserted
with the temperature less than 0°C, or reset
1 On first discharge after NAC ≥ 0.94 ∗ LMD
The first end-of-discharge warning flag (EDV1)
warns the user that the battery is almost empty. The
first segment pin, SEG₁, is modulated at a 4Hz rate if
the display is enabled once EDV1 is asserted, which
should warn the user that loss of battery power is immi-
nent. The EDV1 flag is latched until a valid charge has
been detected. The EDV1 threshold is externally con-
trolled via the VTS register (see Voltage Threshold Reg-
ister).
The EDV1 values are
FLGS1 Bits
7 65 4
3
2
1
0
-
--
-
-
- EDV1 -
where EDV1 is
0 Valid charge action detected, V_SB ≥ V_TS
1 V_SB < V_TS providing that the discharge rate
is < 2C (OVLD not set)
The final end-of-discharge warning flag (EDVF) flag
is used to warn that battery power is at a failure condi-
tion. All segment drivers are turned off. The EDVF flag
is latched until a valid charge has been detected. The
EDVF threshold is set 25mV below the EDV1 threshold.
The EDVF values are
FLGS1 Bits
7 65 4
3
2
-
--
-
-
-
1
0
- EDVF
where EDVF is
0 Valid charge action detected, V_SB ≥ (V_TS - 25mV)
1 V_SB < (V_TS -25mV) providing the discharge
rate is < 2C
Temperature Register (TMP)
The TMP register (address=02h) contains the battery
temperature.
The bq2014H 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 9.
TMP Temperature Bits
7
6
5
4
3
21 0
TMP3 TMP2 TMP1 TMP0 -
-
-
-
The bq2014H calculates the gas gauge bits, GG3-GG0 as a
function of CACT and LMD. The results of the calculation
give available capacity in ¹¹⁶ increments from 0 to ¹⁵¹⁶.
TMP Gas Gauge Bits
76
5
4
3
2
1
0
-
-
-
- GG3 GG2 GG1 GG0
13