BQ2050_15 Datasheet, PDF (5/27 Pages) Texas Instruments – Lithium Ion Power Gauge™ IC

Not Recommended For New Designs
bq2050
Gas Gauge Operation
The operational overview diagram in Figure 2 illustrates
the operation of the bq2050. The bq2050 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 Capacity (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
bq2050 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 VCC 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
EDV1. A qualified discharge is necessary for a capac-
ity transfer from the DCR to the LMD register. The
LMD also serves as the 100% reference threshold
used by the relative display mode.
Inputs
Charge
Current
Rate and
Temperature
Compensation
Discharge
Current
Rate and
Temperature
Compensation
Self-Discharge
Timer
Temperature
Compensation
Main Counters
and Capacity
Reference (LMD)
--
++
< ⁺
Nominal
Available
Last
Measured
Discharge
Count
Charge
Discharged Qualified Register
(NAC)
(LMD) Transfer (DCR)
Temperature
Translation
Temperature Step,
Other Data
Outputs
Compensated
Available Charge
LED Display, etc.
Serial
Port
Figure 2. Operational Overview
FG205002.eps
5