BQ2014_15 Datasheet, PDF (7/27 Pages) Texas Instruments – Gas Gauge IC with External Charge Control

Not Recommended For New Designs
bq2014
The initial full battery capacity is 211mVh
(2110mAh) until the bq2014 “learns” a new capacity
with a qualified discharge from full to EDV1.
3. Nominal Available Charge (NAC):
NAC counts up during charge to a maximum value
of LMD and down during discharge and self-
discharge to 0. NAC is reset to 0 on initialization
and on the first valid charge after EDV = 1. To pre-
vent overstatement of charge during periods of over-
charge, NAC stops incrementing when NAC = LMD.
4. Discharge Count Register (DCR):
The DCR counts up during discharge independent
of NAC and could continue increasing after NAC
has decremented to 0 until VSB < EDV1. Prior to
NAC = 0 (empty battery), both discharge and self-
discharge increment the DCR. After NAC = 0, only
discharge increments the DCR. The DCR resets to
0 when NAC = LMD. The DCR does not roll over
but stops counting when it reaches FFFFh.
The DCR value becomes the new LMD value on the
first charge after a valid discharge to VEDV1 if:
n No valid charges have occurred during the peri-
od between NAC = LMD and EDV1 detected.
n The self-discharge count is not more than 4096
counts (8% to 18% of PFC, specific percentage
threshold determined by PFC).
n The temperature is ≥ 0°C when the EDV1 level
is reached during discharge.
The valid discharge flag (VDQ) indicates whether
the present discharge is valid for LMD update.
Charge Counting
Charge activity is detected based on a positive voltage
on the VSR input. The bq2014 determines charge activ-
ity sustained at a continuous rate equivalent to VSRO
(VSR + VOS) > VSRQ. Once a valid charge is detected,
charge counting continues until VSRO falls below VSRQ.
VSRQ is a programmable threshold (as described in the
Digital Magnitude Filter section) and has a default
value of 375µV. If charge activity is detected, the bq2014
increments the NAC at a rate proportional to VSRO. If
enabled, the bq2014 then activates an LED display.
Charge actions increment the NAC after compensation
for charge rate and temperature.
Charge Control
Charge control is provided by the CHG output. This out-
put is asserted continuously when NAC > 0.94 ∗ LMD.
CHG is also asserted when a valid charge is detected
(CHGS in the FLGS1 register is also set). CHG is low
when NAC < 0.94 ∗ LMD and there is no valid charge ac-
tivity.
DONE Input
When the bq2014 detects a valid charge complete with
an active-high signal on the DONE input, NAC is set to
LMD for
NAC
64
(NiCd)
self-discharge
setting.
NAC is set
to
94%
of
LMD
(if
NAC
is
below
94%)
for
NAC
47
(NiMH)
self-discharge setting. VDQ is set along with DONE.
Discharge Counting
All discharge counts where VSRO < VSRD cause the NAC
register to decrement and the DCR to increment if
EDV1 = 0. Exceeding the fast discharge threshold
(FDQ) if the rate is equivalent to VSRO < -4mV activates
the display, if enabled. The display becomes inactive af-
ter VSRO rises above -4mV. VSRD is a programmable
threshold as described in the Digital Magnitude Fil-
ter section. The default value for VSRD is -300µV.
Self-Discharge Estimation
The bq2014 continuously decrements NAC and incre-
ments DCR for self-discharge based on time and tempera-
ture. The self-discharge count rate is programmed to be a
nominal
1
64
*
NAC
or
1
47
∗
NAC
per
day
or
disabled
as
se-
lected by PROG5. This is the rate for a battery whose
temperature is between 20°C–30°C. The NAC register
cannot be decremented below 0.
Count Compensations
The bq2014 determines fast charge when the NAC up-
dates at a rate of ≥ 2 counts/sec. Charge and discharge
activity is compensated for temperature and charge/dis-
charge rate before updating the NAC and/or DCR. Self-
discharge estimation is compensated for temperature
before updating the NAC or DCR.
Charge Compensation
Two charge efficiency compensation factors are used for
trickle charge and fast charge. Fast charge is defined as
a rate of charge resulting in ≥ 2 NAC counts/sec (≥ 0.15C
to 0.32C depending on PFC selections; see Table 2). The
compensation defaults to the fast charge factor until the
actual charge rate is determined.
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