Datasheet

The compensation factors during discharge are:
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.
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
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
bq2010
Temperature
Range
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
5.88
60–70°C
NAC
4
NAC
2.94
> 70°C
NAC
2
NAC
1.47
Table 3. Self-Discharge Compensation
Approximate
V
SR
Threshold
Discharge
Compensation
Factor Efficiency
V
SR
> -150 mV 1.00 100%
V
SR
< -150 mV 1.05 95%
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