BQ2018TS-E1 Datasheet, PDF (5/25 Pages) Texas Instruments – Power Minder IC

bq2018
7f
73
72
User
RAM
00
7f Discharge count high byte
7e Discharge count low byte
7d Charge count high byte
7c Charge count low byte
7b Self-discharge high byte
7a Self-discharge low byte
79 Discharge time high byte
78 Discharge time low byte
77 Charge time high byte
76 Charge time low byte
75 Mode/wake output enable
74 Temperature/clear
73 Offset register
FG201801.eps
Figure 3. Address Map
During charge, the CCR and the Charge Time Counter
(CTC) are active. If V_SR1 is greater than V_SR2, indicating
a charge, the CCR counts at a rate equivalent to 12.5µV
every hour, and the CTC counts at a rate of 1
count/0.8789 seconds. For example, a +100mV signal pro-
duces 8000 CCR counts and 4096 CTC counts each hour.
The amount of charge added to the battery can easily be
calculated.
The DTC and the CTC are 16-bit registers, and roll over
beyond ffffh. If a rollover occurs, the corresponding bit in
the MODE/WOE register is set, and the counter will sub-
sequently increment at 1/256 of the normal rate (16
counts/hr.).
Whenever the signal between SR1 and SR2 is above the
Wakeup Output Enable (WOE) threshold and the HDQ
pin is high, the bq2018 is in its full operating state. In
this state, the DCR, CCR, DTC, CTC, and SCR are fully
operational, and the WAKE output is low. During this
mode, the internal RAM registers of the bq2018 may be
accessed over the HDQ pin, as described in the section
“Communicating With the 2018.”
If the signal between SR1 and SR2 is below the WOE
threshold (refer to the WAKE section for details) and
HDQ remains low for greater than 10 seconds, the
bq2018 enters a sleep mode where all register counting is
suspended. The bq2018 remains in this mode until HDQ
returns high.
For self-discharge calculation, the self-discharge count
register (SCR) counts at a rate equivalent to 1 count
every hour at a nominal 25°C and doubles approximately
every 10°C up to 60°C. The SCR count rate is halved
every 10 °C below 25°C down to 0°C. The value in SCR is
useful in determining an estimation of the battery self-
discharge based on capacity and storage temperature
conditions.
The bq2018 may be programmed to measure the voltage
offset between SR1 and SR2 during pack assembly or at
any time by invoking the Calibration mode. The Offset
Register (OFR) is used to store the bq2018 offset. The 8-
bit 2’s complement value stored in the OFR is scaled to
the same units as the DCR and CCR, representing the
amount of positive or negative offset in the bq2018. The
maximum offset for the bq2018 is specified as ± 500µV.
Care should be taken to ensure proper PCB layout. Us-
ing OFR, the system host can cancel most of the effects of
bq2018 offset for greater resolution and accuracy.
Figure 3 shows the bq2018 register address map. The
bq2018 uses the upper 13 locations. The remaining
memory can store user-specific information such as
chemistry, serial number, and manufacturing date.
WAKE Output
This output is used to inform the system that the voltage
difference between SR1 and SR2 is above or below the
Wake Output Enable (WOE) threshold programmed in
the MODE/WOE register. When the voltage difference
between SR1 and SR2 is below V_WOE, the WAKE output
goes into High Z and remains in this state until the dis-
charge or charge current increases above the specified
value. The MODE/WOE resets to 0eh after a power-on
reset. V_WOE is set by dividing 3.84mV by a value be-
tween 1 and 7 (1–7h) according to Table 3.
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