BQ2010_15 Datasheet, PDF (8/26 Pages) Texas Instruments – Gas Gauge IC

Not Recommended For New Designs
bq2010
The compensation factors during discharge are:
Approximate
V_SR Threshold
V_SR > -150 mV
V_SR < -150 mV
Discharge
Compensation
Factor
1.00
1.05
Efficiency
100%
95%
Temperature compensation during discharge also takes
place. At lower temperatures, the compensation factor in-
creases by 0.05 for each 10°C temperature step below 10°C.
Comp. factor = 1.0 + (0.05 _* N)
Where N = Number of 10°C steps below 10°C and
-150mV < V_SR < 0.
For example:
T > 10°C : Nominal compensation, N = 0
0°C < T < 10°C: N = 1 (i.e., 1.0 becomes 1.05)
-10°C < T < 0°C: N = 2 (i.e., 1.0 becomes 1.10)
-20°C < T < -10°C: N = 3 (i.e., 1.0 becomes 1.15)
-20°C < T < -30°C: N = 4 (i.e., 1.0 becomes 1.20)
Self-Discharge Compensation
The self-discharge compensation is programmed for a nomi-
nal
rate
of
1
64
*
NAC,
1
47
*
NAC
per
day,
or
disabled.
This is
the rate for a battery within the 20–30°C temperature
range (TMPGG = 6x). This rate varies across 8 ranges from
<10°C to >70°C, doubling with each higher temperature
step (10°C). See Table 3.
Table 3. Self-Discharge Compensation
Temperature
Range
< 10°C
10–20°C
20–30°C
30–40°C
40–50°C
50–60°C
60–70°C
> 70°C
Typical Rate
PROG₅ = Z
NAC
256
NAC
128
NAC
64
NAC
32
NAC
16
NAC
8
NAC
4
NAC
2
PROG₅ = L
NAC
188
NAC
94
NAC
47
NAC
23.5
NAC
11.8
NAC
5.88
NAC
2.94
NAC
1.47
Digital Magnitude Filter
The bq2010 has a programmable digital filter to elimi-
nate charge and discharge counting below a set thresh-
old. The default setting is -0.30mV for V_SRD and
+0.38mV for V_SRQ. The proper digital filter setting can
be calculated using the following equation. Table 4
shows typical digital filter settings.
V_SRD (mV) = -45 / DMF
V_SRQ (mV) = -1.25 _* V_SRD
Table 4. Typical Digital Filter Settings
DMF
75
100
150 (default)
175
200
DMF
Hex.
4B
64
96
AF
C8
V_SRD
(mV)
-0.60
-0.45
-0.30
-0.26
-0.23
V_SRQ
(mV)
0.75
0.56
0.38
0.32
0.28
Error Summary
Capacity Inaccurate
The LMD is susceptible to error on initialization or if no
updates occur. On initialization, the LMD value in-
cludes the error between the programmed full capacity
and the actual capacity. This error is present until a
valid discharge occurs and LMD is updated (see the
DCR description on page 7). The other cause of LMD er-
ror is battery wear-out. As the battery ages, the meas-
ured capacity must be adjusted to account for changes in
actual battery capacity.
A Capacity Inaccurate counter (CPI) is maintained and
incremented each time a valid charge occurs (qualified
by NAC; see the CPI register description) and is reset
whenever LMD is updated from the DCR. The counter
does not wrap around but stops counting at 255. The ca-
pacity inaccurate flag (CI) is set if LMD has not been
updated following 64 valid charges.
Current-Sensing Error
Table 5 illustrates the current-sensing error as a func-
tion of V_SR. A digital filter eliminates charge and dis-
charge counts to the NAC register when V_SRO (V_SR +
V_OS) is between V_SRQ and V_SRD.
Communicating With the bq2010
The bq2010 includes a simple single-pin (DQ plus re-
turn) serial data interface. A host processor uses the in-
terface to access various bq2010 registers. Battery char-
acteristics may be easily monitored by adding a single
contact to the battery pack. The open-drain DQ pin on
8