Datasheet

Temperature adapts the charge rate compensation fac
-
tors over three ranges between nominal, warm, and hot
temperatures. The compensation factors are shown below.
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 V
SR
.
The compensation factors during discharge are:
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 < V
SR
<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
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 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) = -125 ∗ V
SRD
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
bq2014
Approximate
V
SR
Threshold
Discharge
Compensa
-
tion Factor Efficiency
V
SR
> -150 mV 1.00 100%
V
SR
< -150 mV 1.05 95%
Charge
Temperature
Trickle Charge
Compensation
Fast Charge
Compensation
< 40°C 0.80 0.95
> 40°C 0.75 0.90
Temperature
Step
Typical Rate
PROG
5
= Z PROG
5
= L
< 10°C
NAC
256
NAC
188
10–20°C
NAC
128
NAC
94
20–30°C
NAC
64
NAC
47
30–40°C
NAC
32
NAC
23 5.
40–50°C
NAC
16
NAC
11 8.
50–60°C
NAC
8
NAC
588.
60–70°C
NAC
4
NAC
294.
> 70°C
NAC
2
NAC
147.
Table 3. Self-Discharge Compensation
DMF
DMF
Hex.
V
SRD
(mV)
V
SRQ
(mV)
75 4B -0.60 0.75
100 64 -0.45 0.56
150 (default) 96 -0.30 0.38
175 AF -0.26 0.32
200 C8 -0.23 0.28
Table 4. Typical Digital Filter Settings