Datasheet

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 (PROG
6
= Z or low) and on the first valid charge
following discharge to EDV1. NAC is set to PFC on
initialization if PROG
6
= high. To prevent over
-
statement 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. Prior to NAC = 0 (empty
battery), both discharge and self-discharge in
-
crement 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 V
SRO
>V
SRQ
) occurred
during the period between NAC = LMD and EDV1
detected.
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 V
SR
input. If charge activity is detected, the bq2010
increments NAC at a rate proportional to V
SRO
and, if en
-
abled, activates an LED display if the rate is equivalent to
V
SRO
> 4mV. Charge actions increment the NAC after
compensation for charge rate and temperature.
The bq2010 determines charge activity sustained at a
continuous rate equivalent to V
SRO
>V
SRQ
. A valid
charge equates to sustained charge activity greater than
256 NAC counts. Once a valid charge is detected, charge
counting continues until V
SRO
(V
SR
+V
OS
) falls below
V
SRQ
.V
SRQ
is a programmable threshold as described in
the Digital Magnitude Filter section. The default value
for V
SRQ
is 375
µ
V.
Discharge Counting
All discharge counts where V
SRO
<V
SRD
cause the NAC
register to decrement and the DCR to increment. Ex
-
ceeding the fast discharge threshold (FDQ) if the rate is
equivalent to V
SRO
< -4mV activates the display, if en
-
abled. The display becomes inactive after V
SRO
rises
above -4mV. V
SRD
is a programmable threshold as
described in the Digital Magnitude Filter section. The
default value for V
SRD
is -300
µ
V.
Self-Discharge Estimation
The bq2010 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,
1
47
*
NAC per day, or disabled as se
-
lected by PROG
5
. This is the rate for a battery whose
temperature is between 20°–30°C. The NAC register can
-
not be decremented below 0.
Count Compensations
The bq2010 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.
Temperature adapts the charge rate compensation factors
over three ranges between nominal, warm, and hot tem
-
peratures. The compensation factors are shown below.
Discharge Compensation
Corrections for the rate of discharge are made by adjust
-
ing an internal discharge compensation factor. The dis
-
charge compensation factor is based on the namically
measured V
SR
.
7
bq2010
Charge
Temperature
Trickle Charge
Compensation
Fast Charge
Compensation
<30°C 0.80 0.95
30–40°C 0.75 0.90
> 40°C 0.65 0.80