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MAX4063ETE  MAX4063EUD  MAX4063_11  MAX4063  
BQ2011SN Gas Gauge IC for High Discharge Rates
Prototype PCB
Part No.:   BQ2011SN
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Description:   Gas Gauge IC for High Discharge Rates
File Size :   195 K    
Page : 21 Pages
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Maker   TI [ TEXAS INSTRUMENTS ]http://www.ti.com
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bq2011
Gas Gauge Operation
The operational overview diagram in Figure 2 illustrates
the operation of the bq2011. The bq2011 accumulates a
measure of charge and discharge currents, as well as an
estimation of self-discharge. Charge and discharge cur-
rents are temperature and rate compensated, whereas
self-discharge is only temperature compensated.
The main counter, Nominal Available Charge (NAC),
represents the available battery capacity at any given
time. Battery charging increments the NAC register,
while battery discharging and self-discharge decrement
the NAC register and increment the DCR (Discharge
Count Register).
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
bq2011 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 1. 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. A qualified discharge is necessary for a ca-
pacity transfer from the DCR to the LMD register.
The LMD also serves as the 100% reference thresh-
old used by the relative display mode.
2.
Programmed Full Count (PFC) or initial
battery 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
bq2011 is configured for a given application by se-
lecting a PFC value from Table 1. 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.
Inputs
Charge
Current
Rate and
Temperature
Compensation
Discharge
Current
Rate and
Temperature
Compensation
Self-Discharge
Timer
Temperature
Compensation
-
+
Main Counters
and Capacity
Reference (LMD)
-
Measured
<
Discharged
(LMD)
Last
+
+
Nominal
Available
Charge
(NAC)
Discharge
Count
Qualified Register
(DCR)
Transfer
Temperature
Translation
Temperature Step,
Other Data
Outputs
Chip-Controlled
Available Charge
LED Display
Serial
Port
FG201104.eps
Figure 2. Operational Overview
5
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