BQ2010_15 Datasheet, PDF (4/26 Pages) Texas Instruments – Gas Gauge IC

Not Recommended For New Designs
bq2010
Voltage Thresholds
In conjunction with monitoring V_SR for charge/discharge
currents, the bq2010 monitors the single-cell battery
potential through the SB pin. The single-cell voltage
potential is determined through a resistor/divider net-
work according to the following equation:
RB_{1 = N − 1}
RB₂
where N is the number of cells, RB₁ is connected to the
positive battery terminal, and RB₂ is connected to the
negative battery terminal. The single-cell battery volt-
age is monitored for the end-of-discharge voltage (EDV)
and for maximum cell voltage (MCV). EDV threshold
levels are used to determine when the battery has
reached an “empty” state, and the MCV threshold is used
for fault detection during charging.
Two EDV thresholds for the bq2010 are fixed at:
V_EDV1 (early warning) = 1.05V
V_EDVF (empty) = 0.95V
If V_SB is below either of the two EDV thresholds, the as-
sociated flag is latched and remains latched, indepen-
dent of V_SB, until the next valid charge. EDV
monitoring may be disabled under certain conditions as
described in the next paragraph.
During discharge and charge, the bq2010 monitors V_SR
for various thresholds. These thresholds are used to
compensate the charge and discharge rates. Refer to the
count compensation section for details. EDV monitoring
is
disabled
if
V_SR
≤
-250mV
typical
and
resumes
1
2
second
after V_SR > -250mV.
EMPTY Output
The EMPTY output switches to high impedance when
V_SB < V_EDVF and remains latched until a valid charge
occurs. The bq2010 also monitors V_SB relative to V_MCV,
2.25V. V_SB falling from above V_MCV resets the device.
Reset
The bq2010 recognizes a valid battery whenever V_SB is
greater than 0.1V typical. V_SB rising from below 0.25V
or falling from above 2.25V resets the device. Reset can
also be accomplished with a command over the serial
port as described in the Reset Register section.
Temperature
The bq2010 internally determines the temperature in
10°C steps centered from -35°C to +85°C. The tempera-
ture steps are used to adapt charge and discharge rate
compensations, self-discharge counting, and available
charge display translation. The temperature range is
available over the serial port in 10°C increments as
shown below:
TMPGG (hex)
0x
1x
2x
3x
4x
5x
6x
7x
8x
9x
Ax
Bx
Cx
Temperature Range
< -30°C
-30°C to -20°C
-20°C to -10°C
-10°C to 0°C
0°C to 10°C
10°C to 20°C
20°C to 30°C
30°C to 40°C
40°C to 50°C
50°C to 60°C
60°C to 70°C
70°C to 80°C
> 80°C
Layout Considerations
The bq2010 measures the voltage differential between
the SR and V_SS pins. V_OS (the offset voltage at the SR
pin) is greatly affected by PC board layout. For optimal
results, the PC board layout should follow the strict rule
of a single-point ground return. Sharing high-current
ground with small signal ground causes undesirable
noise on the small signal nodes. Additionally:
n _{The capacitors (SB and VCC) should be placed as}
close as possible to the SB and V_CC pins, respectively,
and their paths to V_SS should be as short as possible.
A high-quality ceramic capacitor of 0.1µf is
recommended for V_CC.
n _{The sense resistor capacitor should be placed as close}
as possible to the SR pin.
n _{The sense resistor (RSNS) should be as close as}
possible to the bq2010.
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