Datasheet

perature. Discharge current is load compensated based
on the value stored in location LCOMP (address = 0eh).
LCOMP allows the bq2013H to automatically adjust for
continuous small discharge currents. The bq2013H com
-
pensates self discharge for the load value as well as tem-
perature.
The main counter, Nominal Available Capacity (NAC),
represents the available battery capacity at any given
time. Battery charging increments the NAC register,
while battery discharging, self-discharge decrement the
NAC register and increment the DCR (Discharge Count
Register). NAC is also corrected automatically for offset
error based on the value in the offset location OFFSET
(address = 0bh.)
The Discharge Count Register (DCR) is used to update
the Last Measured Discharge (LMD) register only if a
complete battery discharge from full to empty occurs
without any partial battery charges. Therefore, the
bq2013H adapts its capacity determination based on the
actual conditions of discharge.
The battery’s initial capacity is equal to the Pro-
grammed Full Count (PFC) shown in Table 2. Until
LMD is updated, NAC counts up to but not beyond this
threshold during subsequent charges. This approach al-
lows the gas gauge to be charger-independent and com-
patible with any type of charge regime.
1. Last Measured Discharge (LMD) or learned
battery capacity:
LMD is the last measured discharge capacity of the
battery. On initialization (application of V
CC
or bat-
tery replacement), LMD = PFC. During subsequent
discharges, the LMD is updated with the latest
measured capacity in the Discharge Count Register
(DCR) representing a discharge from full to below
EDV. The maximum decrease in LMD because of a
DCR update is 25% of LMD. A qualified discharge
is necessary for a capacity transfer from the DCR
to the LMD register. The LMD also serves as the
100% reference threshold used by the relative dis-
play mode.
2. Programmed Full Count (PFC) or initial bat-
tery capacity:
The initial LMD and gas gauge rate values are pro-
grammed by using PFC. The PFC also provides the
100% reference for the absolute display mode. The
bq2013H is configured for a given application by se-
lecting a PFC value from Table 2. The correct PFC
may be determined by multiplying the rated bat-
tery capacity in mAh by the sense resistor value:
Battery capacity (mAh)
*
sense resistor (
Ω
) =
PFC (mVh)
Selecting a PFC slightly less than the rated capac-
ity for absolute mode provides capacity above the
full reference for much of the battery’s life.
5
bq2013H
FG2013H2.eps
Load and
Temperature
Compensation
Charge
Current
Discharge
Current
Self-Discharge
Timer
Temperature
Translation
Nominal
Available
Charge
(NAC)
(offset corrected)
Last
Measured
Discharged
(LMD)
Discharge
Count
Register
(DCR)
<
Qualified
Transfer
+
Rate and
Temperature
Compensation
Rate and
Temperature
Compensation
Temperature Step,
Other Data
+
-
Inputs
Main Counters
and Capacity
Reference (LMD)
Outputs
Serial
Port
Chip-Controlled
Available Charge
LED Display
-
+
Load
Compensation
Figure 2. Operational Overview