BQ2014_15 Datasheet, PDF (8/27 Pages) Texas Instruments – Gas Gauge IC with External Charge Control

Not Recommended For New Designs
bq2014
Temperature adapts the charge rate compensation fac-
tors over three ranges between nominal, warm, and hot
temperatures. The compensation factors are shown below.
Charge
Temperature
< 40°C
> 40°C
Trickle Charge
Compensation
0.80
0.75
Fast Charge
Compensation
0.95
0.90
Discharge Compensation
Corrections for the rate of discharge are made by adjust-
ing an internal discharge compensation factor. The dis-
charge factor is based on the dynamically measured VSR.
The compensation factors during discharge are:
Approximate
VSR Threshold
VSR > -150 mV
VSR < -150 mV
Discharge
Compensa-
tion Factor
1.00
1.05
Efficiency
100%
95%
Temperature compensation during discharge also takes place.
At lower temperatures, the compensation factor increases by
0.05 for each 10°C temperature range below 10°C.
Comp. factor = 1.00 + (0.05 _* N)
Where N = number of 10°C steps below 10°C and
-150mV < VSR < 0.
For example:
T > 10°C: Nominal compensation, N = 0
0°C < T < 10°C: N = 1 (i.e., 1.00 becomes 1.05)
-10°C < T < 0°C: N = 2 (i.e., 1.00 becomes 1.10)
-20°C < T < -10°C: N = 3 (i.e., 1.00 becomes 1.15)
-20°C < T < -30°C: N = 4 (i.e., 1.00 becomes 1.20)
Self-Discharge Compensation
The self-discharge compensation is programmed for a
nominal
rate
of
1
64
*
NAC
per
day,
1
47
∗
NAC
per
day,
or
disabled. This is the rate for a battery within the
20°C–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
Step
< 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
PROG5 = L
NAC
256
NAC
128
NAC
64
NAC
32
NAC
16
NAC
8
NAC
4
NAC
2
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 bq2014 has a programmable digital filter to elimi-
nate charge and discharge counting below a set thresh-
old. The default setting is -0.30mV for VSRD and
+0.38mV for VSRQ. The proper digital filter setting can
be calculated using the following equation. Table 4
shows typical digital filter settings.
VSRD (mV) = ^−45
DMF
VSRQ (MV) = -125 ∗ VSRD
Table 4. Typical Digital Filter Settings
DMF
75
100
150 (default)
175
200
DMF
Hex.
4B
64
96
AF
C8
VSRD
(mV)
-0.60
-0.45
-0.30
-0.26
-0.23
VSRQ
(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 up-
dates occur. On initialization, the LMD value includes the
error between the programmed full capacity and the actual
capacity. This error is present until a valid discharge oc-
curs and LMD is updated (see the DCR description on page
7). The other cause of LMD error is battery wear-out. As
the battery ages, the measured 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
8