BQ2012_15 Datasheet, PDF (7/26 Pages) Texas Instruments – Gas Gauge IC With Slow-Charge Control

Not Recommended For New Designs
bq2012
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 initializa-
tion (PROG₆ = Z or low) and on reaching EDV1. NAC
is set to PFC on initialization if PROG₆ = high. To
prevent overstatement of charge during periods of
overcharge, 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. DCR stops counting when
EDV1 is reached. 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 V_EDV1 if:
No valid charge initiations (charges greater than
256 NAC counts; where VSRO > VSRQ) occurred dur-
ing the period between NAC = LMD and EDV1 de-
tected.
The self-discharge count is not more than 4096
counts (8% to 18% of PFC, specific percentage
threshold determined by PFC).
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. If charge activity is detected, the
bq2012 increments NAC at a rate proportional to VSRO
(VSR + VOS) and, if enabled, activates the LED display if
the rate is equivalent to VSRO > 4mV. Charge actions in-
crement the NAC after compensation for charge rate
and temperature.
The bq2012 determines charge activity sustained at a
continuous rate equivalent to VSRO > VSRQ. A valid
charge equates to sustained charge activity greater than
256 NAC counts. 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. The default value for VSRQ is
375µV.
Charge Control
Charge control is provided by the CHG output. This
output is asserted continuously when:
NAC < 0.94 _* LMD and
0.95V < VSB < 2.25V and
0°C < Temp < 50°C and
BRM = 0
This
output
is
asserted
at
a
1
16
duty
cycle
(low
for
0.5
sec
and high for 7.5 sec) when the above conditions are not
met and:
NAC < LMD and
0.95V < VSB < 2.25V and
Temp < 50°C and
BRM = 0
This output is also asserted at a ¹¹⁶ duty cycle (low for 0.5 sec
and high for 7.5 sec) for a 2-hour top-off period after:
NAC = LMD and
Temp < 50°C and
0.95V < VSB < 2.25V and
BRM = 0
This output is inactive when:
NAC = LMD (after a 2-hour top-off period) or
Temp > 50°C or
VSB < 0.95V or
VSB > 2.25V or
BRM = 1
The top-off timer (2 hours) is reset to allow another top-
off after the battery is discharged to 0.8 _* LMD (PROG6
= L) or 0.8 _* PFC (PROG6 = Z or H).
Caution: The charge control output (CHG) should
be used with other forms of charge termination
such as ∆T/∆t and -∆V.
If charge terminates due to maximum temperature, the
battery temperature must fall typically 10°C below 50°C
before the charge output becomes active again.
Discharge Counting
All discharge counts where VSRO < VSRD cause the NAC
register to decrement and the DCR to increment. Ex-
ceeding the fast discharge threshold (FDQ) if the rate is
equivalent to VSRO < -4mV activates the display, if en-
abled. The display becomes inactive after VSRO rises
above -4mV. VSRD is a programmable threshold as
described in the Digital Magnitude Filter section. The
default value for VSRD is -300µV.
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