BQ2092_15 Datasheet, PDF (6/30 Pages) Texas Instruments – Gas Gauge IC with SMBus-Like Interface

Obsolete Device
bq2092
Inputs
Charge
Current
Rate and
Temperature
Compensation
Discharge
Current
Rate and
Temperature
Compensation
Self-Discharge
Timer
Temperature
Compensation
Main Counters
and Capacity
Reference (FCC)
--
< + Remaining
Capacity
(RM)
Full
Charge
Capacity
(FCC)
++
Discharge
Count
Qualified _Register
Transfer _(DCR)
Temperature, Other Data
Outputs
Chip-Controlled Two-Wire
Available Charge Serial Interface
LED Display
Figure 2. Operational Overview
2. DesignCapacity (DC):
The DC is the user-specified battery capacity and is
programmed by using an external EEPROM. The
DC also provides the 100% reference for the abso-
lute display mode.
3. Remaining Capacity (RM):
n The temperature is ≥ 273°K (0°C) when the
EDV1 level is reached during discharge.
The valid discharge flag (VDQ) indicates whether
the present discharge is valid for FCC update. FCC
cannot be reduced by more than 256mAh during
any single cycle.
RM counts up during charge to a maximum value of ^{Charge Counting}
FCC and down during discharge and self-discharge to
0. RM is reset to 0000Ah when EDV1 = 1 and a valid
charge is detected. To prevent overstatement of
charge during periods of overcharge, RM stops in-
crementing when RM = FCC. RM may optionally
be written to a user-defined value when fully
charged when the battery pack is under bq2092
Charge activity is detected based on a positive voltage
on the VSR input. If charge activity is detected, the
bq2092 increments RM at a rate proportional to VSRO
and, if enabled, activates an LED display. Charge
actions increment the RM after compensation for charge
rate and temperature.
charge control. See the Charge Control section for _{The bq2092 determines charge activity sustained at a}
further details.
continuous rate equivalent to VSRO > |VSRD|. A valid
4. Discharge Count Register (DCR):
charge equates to sustained charge activity
greater than 10 mAh. Once a valid charge is detected,
The DCR counts up during discharge independent charge counting continues until VSRO falls below
of RM and can continue increasing after RM has |VSRD|. VSRD is a programmable threshold as
decremented to 0. Before RM = 0 (empty battery), described in the Digital Magnitude Filter section.
both discharge and self-discharge increment the
DCR. After RM = 0, only discharge increments Discharge Counting
the DCR. The DCR resets to 0 when RM = FCC.
The DCR does not roll over but stops counting
when it reaches FFFFh.
All discharge counts where VSRO < |VSRD| cause the
RM register to decrement and the DCR to increment.
VSRD is a programmable threshold as described in the
The DCR value becomes the new FCC value on the Digital Magnitude Filter section.
first charge after a valid discharge to VEDV1 if:
Self-Discharge Estimation
n No valid charge initiations (charges greater than
10mAh, where VSRO > |VSRD|) occurred during The bq2092 continuously decrements RM and incre-
the period between RM = FCC and EDV1 de- ments DCR for self-discharge based on time and
tected.
temperature. The self-discharge rate is dependent on
n The self-discharge count is not more than
256mAh.
the battery chemistry. The bq2092 self-discharge esti-
mation rate is externally programmed in EEPROM
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