BQ2014H_15 Datasheet, PDF (8/28 Pages) Texas Instruments – Low-Cost NiCd/NiMH Gas Gauge IC

bq2014H
Count Compensations
Charge Compensation
Two charge efficiency compensation factors are used for
trickle and fast charge. Trickle charge is defined as a rate
of charge < C/3. The compensation defaults to the fast-
charge factor until the actual charge rate is determined.
Temperature adapts the charge rate compensation fac-
tors over two ranges between nominal and hot tempera-
tures. The compensation factors are shown below.
Charge
Temperature
< 40°C
> 40°C
Trickle-Charge
Compensation
0.81
0.75
Fast-Charge
Compensation
0.94
0.88
Compensated Available Capacity
NAC is adjusted for rate of discharge and temperature
to derive the CACD and CACT values.
Corrections for the rate of discharge are made by adjust-
ing an internal discharge compensation factor. The dis-
charge factor is based on the discharge rate. This com-
pensation is applied to NAC to derive the value in the
CACD register.
The compensation factors during discharge are:
Approximate
Discharge Rate
< 2C
> 2C
Rate Efficiency
Factor
100%
95%
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
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
with each higher temperature step (10°C). See Table 3.
Digital Magnitude Filter
The bq2014H has a digital filter to eliminate charge and
discharge counting below a set threshold. The threshold
for both V_SRD and V_SRQ is 250µV_.
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. This compensation is applied to CACD to derive
the value in the CACT register. The temperature com-
pensation factor follows the equation
Temperature Efficiency Factor = 1.00 - (0.05 ∗ N)
where N = number of 10°C steps below 10°C.
For example,
T > 10°C: Nominal compensation, N = 0
0°C < T < 10°C: N = 1 (temperature efficiency = 95%)
-10°C < T < 0°C: N = 2 (temperature efficiency = 90%)
-20°C < T < -10°C: N = 3 (temperature efficiency = 85%)
-20°C < T < -30°C: N = 4 (temperature efficiency = 80%)
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