TI BQ2011SN-D118

bq2011
Gas Gauge IC for
High Discharge Rates
Features
General Description
➤ Conservative and repeatable
measurement of available charge
in rechargeable batteries
The bq2011 Gas Gauge IC is intended
for battery-pack installation to maintain an accurate record of available
battery charge. The IC monitors a
voltage drop across a sense resistor
connected in series between the negative battery terminal and ground to
determine charge and discharge activity of the battery. The bq2011 is
designed for systems such as power
tools with very high discharge rates.
➤ Designed for portable equipment
such as power tools with high discharge rates
➤ Designed for battery pack integration
-
120µA typical standby current
(self-discharge estimation mode)
-
Small size enables implementations in as little as 1 2
square inch of PCB
➤ Direct drive of LEDs for capacity
display
➤ Self-discharge compensation using internal temperature sensor
➤ Simple single-wire serial communications port for subassembly
testing
➤ 16-pin narrow SOIC
Pin Connections
1
16
VCC
SEG1
2
15
REF
SEG2
3
14
NC
4
The bq2011 supports a simple singleline bidirectional serial link to an external processor (common ground). The
bq2011 outputs battery information in
response to external commands over the
serial link. To support subassembly
testing, the outputs may also be controlled by command. The external processor may also overwrite some of the
bq2011 gas gauge data registers.
The bq2011 may operate directly
from four cells. With the REF output
and an external transistor, a simple,
inexpensive regulator can be built to
provide VCC from a greater number
of cells.
Internal registers include available
charge, temperature, capacity, battery
ID, and battery status.
Pin Names
MODE
SEG3
Battery self-discharge is estimated
based on an internal timer and temperature sensor. Compensations for
battery temperature and rate of
charge or discharge are applied to
the charge, discharge, and
selfdischarge calculations to provide
available charge information across
a wide range of operating conditions.
Initial battery capacity is set using
the PFC and MODE pins. Actual
battery capacity is automatically
“learned” in the course of a discharge cycle from full to empty and
may be displayed depending on the
display mode.
Nominal available charge may be directly indicated using a five-segment LED display. These segments
are used to indicate graphically the
nominal available charge.
13
DQ
MODE
Display mode output
NC
No connect
SEG1
LED segment 1
DQ
Serial communications
input/output
SEG2
LED segment 2
RBI
Register backup input
SEG3
LED segment 3
SB
Battery sense input
SEG4
LED segment 4
DISP
Display control input
SEG4
5
12
RBI
SEG5
6
11
SB
SEG5
LED segment 5
SR
Sense resistor input
PFC
7
10
DISP
PFC
Programmed full count
selection input
VCC
3.0–6.5V
VSS
8
9
Voltage reference output
VSS
Negative battery terminal
SR
REF
16-Pin Narrow SOIC
PN201101.eps
2/96 E
1
bq2011
DISP
Pin Descriptions
MODE
DISP floating allows the LED display to
be active during charge and discharge if
VSRO < -1mV (charge) or VSRO > 2mV (discharge). Transitioning DISP low activates
the display for 4 ± 0.5 seconds.
Display mode output
When left floating, this output selects relative mode for capacity display. If connected
to the anode of the LEDs to source current,
absolute mode is selected for capacity display. See Table 1.
SEG1–
SEG5
SB
RBI
Programmed full count selection input
DQ
Sense resistor input
Serial I/O pin
This is an open-drain bidirectional pin.
The voltage drop (VSR) across the sense resistor RS is monitored and integrated over
time to interpret charge and discharge activity. The SR input is tied to the low side of
the sense resistor. VSR > VSS indicates discharge, and VSR < VSS indicates charge. The
effective voltage drop, VSRO, as seen by the
bq2011 is VSR + VOS (see Table 3).
NC
Register backup input
This input is used to provide backup potential
to the bq2011 registers during periods when
VCC ≤ 3V. A storage capacitor should be connected to RBI.
This three-level input pin defines the programmed full count (PFC) thresholds and
scale selections described in Table 1. The
state of the PFC pin is only read immediately after a reset condition.
SR
Secondary battery input
This input monitors the single-cell voltage
potential through a high-impedance resistive divider network for the end-of-discharge
voltage (EDV) threshold and maximum cell
voltage (MCV).
LED display segment outputs
Each output may activate an LED to sink
the current sourced from MODE, the battery, or VCC.
PFC
Display control input
REF
Voltage reference output for regulator
REF provides a voltage reference output for
an optional micro-regulator.
No connect
2
VCC
Supply voltage input
VSS
Ground
bq2011
Figure 1 shows a typical battery pack application of the
bq2011 using the LED display with absolute mode as a
charge-state indicator. The bq2011 can be configured to
display capacity in either a relative or an absolute display mode. The relative display mode uses the last
measured discharge capacity of the battery as the battery “full” reference. The absolute display mode uses the
programmed full count (PFC) as the full reference, forcing each segment of the display to represent a fixed
amount of charge. A push-button display feature is
available for momentarily enabling the LED display.
Functional Description
General Operation
The bq2011 determines battery capacity by monitoring
the amount of charge input to or removed from a rechargeable battery. The bq2011 measures discharge and
charge currents, estimates self-discharge, monitors the
battery for low-battery voltage thresholds, and compensates for temperature and charge/discharge rates. The
charge measurement is made by monitoring the voltage
across a small-value series sense resistor between the
negative battery terminal and ground. The available
battery charge is determined by monitoring this voltage
over time and correcting the measurement for the environmental and operating conditions.
The bq2011 monitors the charge and discharge currents
as a voltage across a sense resistor (see RS in Figure 1).
A filter between the negative battery terminal and the
SR pin may be required if the rate of change of the battery current is too great.
R1
bq2011
Gas Gauge IC
Q1
ZVNL110A
REF
MODE
SEG1
C1
0.1 F
VCC
RB1
VCC
SB
SEG2
RB2
SEG3
DISP
SEG4
VSS
SEG5
SR
RS
PFC
RBI
DQ
Charger
Indicates optional.
Directly connect to VCC across 4 cells (4.8V nominal and should not
exceed 6.5V) with a resistor and a Zener diode to limit voltage during charge.
Otherwise, R1, C1, and Q1 are needed for regulation of >4 cells.
Load
Programming resistors and ESD-protection diodes are not shown.
R-C on SR may be required, (application-specific), where the maximum
R should not exceed 20K.
FG201101.eps
Figure 1. Battery Pack Application Diagram—LED Display,
Absolute Mode
3
bq2011
charge display translation. The temperature range is
available over the serial port in 10°C increments as
shown below:
Register Backup
The bq2011 RBI input pin is intended to be used with a
storage capacitor to provide backup potential to the internal bq2011 registers when VCC momentarily drops below
3.0V. VCC is output on RBI when VCC is above 3.0V.
TMPGG (hex)
Temperature Range
After VCC rises above 3.0V, the bq2011 checks the internal registers for data loss or corruption. If data has
changed, then the NAC and FULCNT registers are
cleared, and the LMD register is loaded with the initial
PFC.
0x
< -30°C
1x
-30°C to -20°C
2x
-20°C to -10°C
Voltage Thresholds
3x
-10°C to 0°C
In conjunction with monitoring VSR for charge/discharge
currents, the bq2011 monitors the single-cell battery potential through the SB pin. The single-cell voltage potential is determined through a resistor-divider network
per the following equation:
4x
0°C to 10°C
5x
10°C to 20°C
6x
20°C to 30°C
7x
30°C to 40°C
8x
40°C to 50°C
9x
50°C to 60°C
Ax
60°C to 70°C
Bx
70°C to 80°C
Cx
> 80°C
RB1
= 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 voltage is monitored for the end-of-discharge voltage (EDV)
and for maximum cell voltage (MCV). The EDV threshold level is used to determine when the battery has
reached an “empty” state, and the MCV threshold is used
for fault detection during charging. The EDV and MCV
thresholds for the bq2011 are fixed at:
VEDV = 0.90V
VMCV = 2.00V
Layout Considerations
The bq2011 measures the voltage differential between
the SR and VSS pins. VOS (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:
During discharge and charge, the bq2011 monitors VSR
for various thresholds, VSR1–VSR4. These thresholds are
used to compensate the charge and discharge rates. Refer to the discharge compensation section for details.
EDV monitoring is disabled if VSR > VSR1 (50mV typical)
and resumes 1 second after VSR drops back below VSR1.
Reset
n
The bq2011 recognizes a valid battery whenever VSB is
greater than 0.1V typical. VSB rising from below 0.25V
resets the device. Reset can also be accomplished with a
command over the serial port as described in the Reset
Register section.
The capacitors (SB and VCC) should be placed as close
as possible to the SB and VCC pins, respectively, and
their paths to VSS should be as short as possible. A
high-quality ceramic capacitor of 0.1µf is recommended
for VCC.
n
The sense resistor (RS) should be as close as possible
to the bq2011.
n
The R-C on the SR pin should be located as close as
possible to the SR pin. The maximum R should not
exceed 20K.
Temperature
The bq2011 internally determines the temperature in
10°C steps centered from -35°C to +85°C. The temperature steps are used to adapt charge and discharge rate
compensations, self-discharge counting, and available
4
bq2011
1.
Gas Gauge Operation
Last Measured Discharge (LMD) or
learned battery capacity:
The operational overview diagram in Figure 2 illustrates
the operation of the bq2011. The bq2011 accumulates a
measure of charge and discharge currents, as well as an
estimation of self-discharge. Charge and discharge currents are temperature and rate compensated, whereas
self-discharge is only temperature compensated.
LMD is the last measured discharge capacity of the
battery. On initialization (application of VCC or battery replacement), LMD = PFC. During subsequent
discharges, the LMD is updated with the latest
measured capacity in the Discharge Count Register
(DCR) representing a discharge from full to below
EDV. A qualified discharge is necessary for a capacity transfer from the DCR to the LMD register.
The LMD also serves as the 100% reference threshold used by the relative display mode.
The main counter, Nominal Available Charge (NAC),
represents the available battery capacity at any given
time. Battery charging increments the NAC register,
while battery discharging and self-discharge decrement
the NAC register and increment the DCR (Discharge
Count Register).
2.
Programmed Full Count (PFC) or initial
battery capacity:
The Discharge Count Register (DCR) is used to update
the Last Measured Discharge (LMD) register only if a
complete battery discharge from full to empty occurs
without any partial battery charges. Therefore, the
bq2011 adapts its capacity determination based on the
actual conditions of discharge.
The initial LMD and gas gauge rate values are programmed by using PFC. The PFC also provides the
100% reference for the absolute display mode. The
bq2011 is configured for a given application by selecting a PFC value from Table 1. The correct PFC
may be determined by multiplying the rated battery capacity in mAh by the sense resistor value:
The battery's initial capacity is equal to the Programmed Full Count (PFC) shown in Table 1. Until
LMD is updated, NAC counts up to but not beyond this
threshold during subsequent charges. This approach allows the gas gauge to be charger-independent and compatible with any type of charge regime.
Inputs
PFC (mVh)
Selecting a PFC slightly less than the rated capacity for absolute mode provides capacity above the
full reference for much of the battery's life.
Charge
Current
Discharge
Current
Self-Discharge
Timer
Rate and
Temperature
Compensation
Rate and
Temperature
Compensation
Temperature
Compensation
+
Main Counters
and Capacity
Reference (LMD)
Battery capacity (mAh) * sense resistor (Ω) =
+
-
Nominal
Available
Charge
(NAC)
<
Last
Measured
Discharged
(LMD)
Temperature Step,
Other Data
Temperature
Translation
Outputs
Chip-Controlled
Available Charge
LED Display
+
Discharge
Count
Qualified Register
(DCR)
Transfer
Serial
Port
FG201104.eps
Figure 2. Operational Overview
5
bq2011
Select:
Example: Selecting a PFC Value
PFC = 34304 counts or 6.5mVh
PFC = Z (float)
MODE = not connected
Given:
Sense resistor = 0.005Ω
Number of cells = 6
Capacity = 1300mAh, NiCd cells
Current range = 1A to 80A
Relative display mode
Self-discharge = C 64
Voltage drop over sense resistor = 5mV to 400mV
The initial full battery capacity is 6.5mVh
(1300mAh) until the bq2011 “learns” a new capacity with a qualified discharge from full to EDV.
Therefore:
1300mAh * 0.005Ω = 6.5mVh
Table 1. bq2011 Programmed Full Count mVh Selections
PFC
Programmed
Full Count (PFC)
mVh
H
27648
10.5
1
Z
34304
6.5
1
L
44800
8.5
1
H
42240
8.0
1
Z
31744
6.0
1
L
23808
4.5
1
Scale
MODE Pin
Display Mode
Floating
Relative
Connected to LEDs
Absolute
2640
5280
5280
5280
5280
5280
6
bq2011
3.
Nominal Available Charge (NAC):
Discharge Counting
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 following discharge to EDV.
To prevent overstatement of charge during periods
of overcharge, NAC stops incrementing when NAC
= LMD.
All discharge counts where VSRO > 500µV cause the
NAC register to decrement and the DCR to increment.
Exceeding the fast discharge threshold (FDQ) if the rate
is equivalent to VSRO > 2mV activates the display, if enabled. The display becomes inactive after VSRO falls below 2mV.
Self-Discharge Estimation
Note: NAC is set to the value in LMD when SEG5
is pulled low during a reset.
4.
The bq2011 continuously decrements NAC and increments DCR for self-discharge based on time and temperature. The self-discharge count rate is programmed to be a
nominal 1 80 * NAC rate per day. This is the rate for a battery whose temperature is between 20°–30°C. The NAC
register cannot be decremented below 0.
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 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.
Count Compensations
The bq2011 determines fast charge when the NAC updates at a rate of ≥2 counts/sec. Charge and discharge
activity is compensated for temperature and charge/discharge rate before updating the NAC and/or DCR. Selfdischarge estimation is compensated for temperature
before updating the NAC or DCR.
The DCR value becomes the new LMD value on the
first charge after a valid discharge to VEDV if:
n
n
n
No valid charge initiations (charges greater than
256 NAC counts; or 0.006 – 0.01C) occurred during the period between NAC = LMD and EDV
detected.
Charge Compensation
Two charge efficiency 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.
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 EDV level is
reached during discharge.
Temperature adapts the charge rate compensation factors over three ranges between nominal, warm, and hot
temperatures. The compensation factors are shown below.
The valid discharge flag (VDQ) indicates whether
the present discharge is valid for LMD update.
Charge Counting
Charge activity is detected based on a negative voltage
on the VSR input. If charge activity is detected, the
bq2011 increments NAC at a rate proportional to VSRO
(VSR + VOS) and, if enabled, activates an LED display
if VSRO < -1mV. Charge actions increment the NAC after compensation for charge rate and temperature.
The bq2011 determines a valid charge activity sustained
at a continuous rate equivalent to VSRO < -400µV. A
valid charge equates to a sustained charge activity
greater than 256 NAC counts. Once a valid charge is detected, charge counting continues until V SRO rises
above -400µV.
7
Charge
Temperature
Trickle Charge
Compensation
Fast Charge
Compensation
<40°C
0.80
0.95
≥ 40°C
0.75
0.90
bq2011
Discharge Compensation
Table 2. Self-Discharge Compensation
Corrections for the rate of discharge are made by adjusting an internal discharge compensation factor. The discharge factor is based on the dynamically measured VSR.
The compensation factors during discharge are:
NAC
10–20°C
NAC
20–30°C
NAC
30–40°C
NAC
40–50°C
NAC
75%
50–60°C
NAC
75%
60–70°C
NAC
Approximate
VSR Threshold
Efficiency
VSR < 50 mV
1.00
100%
VSR1 > 50 mV
1.05
95%
VSR2 > 100 mV
1.15
VSR4 > 253 mV
85%
1.25
1.25
Self-Discharge Compensation
Typical Rate/Day
< 10°C
Discharge
Compensation
Factor
VSR3 > 150 mV
Temperature
Range
> 70°C
Temperature compensation during discharge also takes place.
At lower temperatures, the compensation factor increases by
0.05 for each 10°C temperature step below 10°C.
NAC
320
160
80
40
20
10
5
2 .5
Error Summary
Comp. factor = 1.00 + (0.05 * N)
Capacity Inaccurate
Where N = number of 10°C steps below 10°C and
V SR < 50mV.
The LMD is susceptible to error on initialization or if no updates occur. On initialization, the LMD value includes the
error between the programmed full capacity and the actual
capacity. This error is present until a valid discharge occurs and LMD is updated (see the DCR description on page
7). The other cause of LMD error is battery wear-out. As
the battery ages, the measured capacity must be adjusted
to account for changes in actual battery capacity.
For example:
T > 10°C: Nominal compensation, N = 0
0°C < T < 10°C: N = 1 (i.e., 1.00 becomes 1.05)
-10°C < T < 0°C: N = 2 (i.e., 1.00 becomes 1.10)
A Capacity Inaccurate counter (CPI) is maintained and
incremented each time a valid charge occurs and is reset
whenever LMD is updated from the DCR. The counter
does not wrap around but stops counting at 255. The capacity inaccurate flag (CI) is set if LMD has not been
updated following 64 valid charges.
-20°C < T < -10°C: N = 3 (i.e., 1.00 becomes 1.15)
-20°C < T < -30°C: N = 4 (i.e., 1.00 becomes 1.20)
Self-Discharge Compensation
The self-discharge compensation is programmed for a
nominal rate of 1 80 * NAC per day. This is the rate for a
battery within the 20–30°C temperature range (TMPGG
= 6x). This rate varies across 8 ranges from <10°C to
>70°C, doubling with each higher temperature step
(10°C). See Table 2
Current-Sensing Error
Table 3 illustrates the current-sensing error as a function of V SR . A digital filter eliminates charge and
discharge counts to the NAC register when VSRO (VSR +
VOS) is between -400µV and 500µV.
Table 3. bq2011 Current-Sensing Errors
Symbol
INL
INR
Parameter
Integrated non-linearity
error
Integrated nonrepeatability error
Typical
Maximum
Units
±2
±4
%
±1
±2
%
8
Notes
Add 0.1% per °C above or below 25°C
and 1% per volt above or below 4.25V.
Measurement repeatability given
similar operating conditions.
bq2011
logic-low state for a period, tSTRH,B. The next section is the
actual data transmission, where the data should be valid by
a period, tDSU, after the negative edge used to start communication. The data should be held for a period, tDV, to allow
the host or bq2011 to sample the data bit.
Communicating with the bq2011
The bq2011 includes a simple single-pin (DQ plus return) serial data interface. A host processor uses the interface to access various bq2011 registers. Battery characteristics may be easily monitored by adding a single
contact to the battery pack. The open-drain DQ pin on
the bq2011 should be pulled up by the host system, or may
be left floating if the serial interface is not used.
The final section is used to stop the transmission by returning the DQ pin to a logic-high state by at least a period,
tSSU, after the negative edge used to start communication.
The final logic-high state should be held until a period, tSV,
to allow time to ensure that the bit transmission was
stopped properly. The timings for data and break communication are given in the serial communication timing
specification and illustration sections.
The interface uses a command-based protocol, where the
host processor sends a command byte to the bq2011.
The command directs the bq2011 to either store the next
eight bits of data received to a register specified by the
command byte or output the eight bits of data specified
by the command byte.
Communication with the bq2011 is always performed
with the least-significant bit being transmitted first.
Figure 3 shows an example of a communication sequence to read the bq2011 NAC register.
The communication protocol is asynchronous return-toone. Command and data bytes consist of a stream of eight
bits that have a maximum transmission rate of 333
bits/sec. The least-significant bit of a command or data
byte is transmitted first. The protocol is simple enough
that it can be implemented by most host processors using
either polled or interrupt processing. Data input from the
bq2011 may be sampled using the pulse-width capture
timers available on some microcontrollers.
bq2011 Registers
The bq2011 command and status registers are listed in
Table 4 and described below.
Command Register (CMDR)
Communication is normally initiated by the host processor sending a BREAK command to the bq2011. A
BREAK is detected when the DQ pin is driven to a
logic-low state for a time, tB or greater. The DQ pin
should then be returned to its normal ready-high logic
state for a time, tBR. The bq2011 is now ready to receive
a command from the host processor.
The write-only CMDR register is accessed when eight
valid command bits have been received by the bq2011.
The CMDR register contains two fields:
W/R bit
n
Command address
The W/R bit of the command register is used to select
whether the received command is for a read or a write
function.
The return-to-one data bit frame consists of three distinct
sections. The first section is used to start the transmission
by either the host or the bq2011 taking the DQ pin to a
Written by Host to bq2011
CMDR = 03h
LSB
n
Received by Host to bq2011
NAC = 65h
MSB
Break 1 1 0 0 0 0 0 0
LSB
MSB
1 0 1 0 011 0
DQ
TD201101.eps
Figure 3. Typical Communication with the bq2011
9
bq2011
Table 4. bq2011 Command and Status Registers
Symbol
Register
Name
Control Field
Loc.
(hex)
Read/
Write
7(MSB)
6
5
4
3
2
1
0(LSB)
CMDR
Command
register
00h
Write
W/R
AD6
AD5
AD4
AD3
AD2
AD1
AD0
FLGS1
Primary
status flags
register
01h
Read
CHGS
BRP
MCV
CI
VDQ
n/u
EDV
n/u
Temperature
TMPGG and gas gauge 02h
register
Read
TMP3
TMP2
TMP1
TMP0
GG3
GG2
GG1
GG0
NACH
Nominal
available
charge high
byte register
03h
R/W
NACH7 NACH6 NACH5 NACH4 NACH3 NACH2 NACH1 NACH0
NACL
Nominal
available
charge low
byte register
17h
Read
NACL7 NACL6
BATID
Battery
identification
register
04h
R/W
BATID7 BATID6 BATID5 BATID4 BATID3 BATID2 BATID1 BATID0
LMD
Last measured discharge register
05h
R/W
LMD7
LMD6
LMD5
LMD4
LMD3
LMD2
LMD1
LMD0
FLGS2
Secondary
status flags
register
06h
Read
CR
DR2
DR1
DR0
n/u
n/u
n/u
OVLD
CPI
Capacity
inaccurate
count register
09h
Read
CPI7
CPI6
CPI5
CPI4
CPI3
CPI2
CPI1
CPI0
OCTL
Output control register
0ah
Write
1
OC5
OC4
OC3
OC2
OC1
n/u
OCE
FULCNT
Full count
register
0bh
Read
FUL7
FUL6
FUL5
FUL4
FUL3
FUL2
FUL1
FUL0
RST
Reset register
39h
Write
RST
0
0
0
0
0
0
0
Note:
n/u = not used
10
NACL5
NACL4 NACL3 NACL2 NACL1 NACL0
bq2011
The BRP values are:
The W/R values are:
CMDR Bits
FLGS1 Bits
7
6
5
4
3
2
1
0
7
6
5
4
3
2
1
0
W/R
-
-
-
-
-
-
-
-
BRP
-
-
-
-
-
-
Where BRP is:
Where W/R is:
0
The bq2011 outputs the requested register
contents specified by the address portion of
CMDR.
1
The following eight bits should be written
to the register specified by the address portion of CMDR.
0
bq2011 is charged until NAC = LMD or discharged until the EDV flag is asserted
1
SB rising from below 0.1V, or a serial port
initiated reset has occurred
The maximum cell voltage flag (MCV) is asserted
whenever the potential on the SB pin (relative to VSS) is
above 2.0V. The MCV flag is asserted until the condition causing MCV is removed.
The lower seven-bit field of CMDR contains the address
portion of the register to be accessed. Attempts to write
to invalid addresses are ignored.
The MCV values are:
CMDR Bits
7
-
6
5
AD6 AD5
FLGS1 Bits
4
3
2
1
0
AD4
AD3
AD2
AD1
AD0
(LSB)
7
6
5
4
3
2
1
0
-
-
MCV
-
-
-
-
-
Where MCV is:
Primary Status Flags Register (FLGS1)
The read-only FLGS1 register (address=01h) contains
the primary bq2011 flags.
0
VSB < 2.0V
1
VSB > 2.0V
The capacity inaccurate flag (CI) is used to warn the
user that the battery has been charged a substantial
number of times since LMD has been updated. The CI
flag is asserted on the 64th charge after the last LMD
update or when the bq2011 is reset. The flag is cleared
after an LMD update.
The charge status flag (CHGS) is asserted when a
valid charge rate is detected. Charge rate is deemed
valid when VSRO < -400µV. A VSRO of greater than400µV or discharge activity clears CHGS.
The CHGS values are:
The CI values are:
FLGS1 Bits
7
6
5
4
3
2
1
0
CHGS
-
-
-
-
-
-
-
FLGS1 Bits
Where CHGS is:
0
Either discharge activity detected or VSRO >
-400µV
1
VSRO < -400µV
7
6
5
4
3
2
1
0
-
-
-
CI
-
-
-
-
Where CI is:
The battery replaced flag (BRP) is asserted whenever
the potential on the SB pin (relative to VSS), VSB, rises
above 0.1V and determines the internal registers have
been corrupted. The BRP flag is also set when the
bq2011 is reset (see the RST register description). BRP
is latched until either the bq2011 is charged until NAC
= LMD or discharged until EDV is reached. BRP = 1
signifies that the device has been reset.
11
0
When LMD is updated with a valid full discharge or the bq2011 is reset
1
After the 64th valid charge action with no
LMD updates
bq2011
The valid discharge flag (VDQ) is asserted when the
bq2011 is discharged from NAC=LMD. The flag remains
set until either LMD is updated or one of three actions
that can clear VDQ occurs:
n
TMPGG Temperature Bits
7
The self-discharge count register (SDCR) has
exceeded the maximum acceptable value (4096
counts) for an LMD update.
n
A valid charge action equal to 256 NAC counts with
VSRO < -400µV.
n
The EDV flag was set at a temperature below 0°C
5
4
3
2
1
0
-
-
-
-
VDQ
-
-
-
SDCR ≥ 4096, subsequent valid charge action detected, or EDV is asserted with the
temperature less than 0°C
1
On first discharge after NAC = LMD
4
3
2
1
0
-
-
-
-
-
-
EDV
-
-
0
Temperature
0
0
0
0
T < -30°C
0
0
0
1
-30°C < T < -20°C
0
0
1
0
-20°C < T < -10°C
0
0
1
1
-10°C < T < 0°C
0
1
0
0
0°C < T < 10°C
0
1
0
1
10°C < T < 20°C
0
1
1
0
20°C < T < 30°C
0
1
1
1
30°C < T < 40°C
1
0
0
0
40°C < T < 50°C
1
0
0
1
50°C < T < 60°C
1
0
1
0
60°C < T < 70°C
1
0
1
1
70°C < T < 80°C
1
1
0
0
T > 80°C
FLGS1 Bits
5
1
-
TMP0
The EDV values are:
6
2
-
TMP1
The end-of-discharge warning flag (EDV) warns the
user that the battery is empty. SEG1 blinks at a 4Hz
rate. EDV detection is disabled if VSR > VSR1. The EDV
flag is latched until a valid charge has been detected.
7
3
TMP2
Where VDQ is:
0
4
TMP3
FLGS1 Bits
6
5
TMP1 TMP0
The bq2011 contains an internal temperature sensor.
The temperature is used to set charge and discharge efficiency factors as well as to adjust the self-discharge coefficient. The temperature register contents may be
translated as shown below.
The VDQ values are:
7
6
TMP3 TMP2
Where EDV is:
0
Valid charge action detected and VSB ≥
0.90V
1
VSB < 0.90V providing that VSR < VSR1
The bq2011 calculates the available charge as a function
of NAC, temperature, and a full reference, either LMD
or PFC. The results of the calculation are available via
the display port or the gas gauge field of the TMPGG
register. The register is used to give available capacity
in 116 increments from 0 to 1516.
Temperature and Gas Gauge Register
(TMPGG)
TMPGG Gas Gauge Bits
The read-only TMPGG register (address=02h) contains
two data fields. The first field contains the battery temperature. The second field contains the available charge
from the battery.
12
7
6
5
4
3
2
1
0
-
-
-
-
GG3
GG2
GG1
GG0
bq2011
The CR values are:
The gas gauge display and the gas gauge portion of the
TMPGG register are adjusted for cold temperature dependencies. A piece-wise correction is performed as follows:
Temperature
FLGS2 Bits
7
6
5
4
3
2
1
0
CR
-
-
-
-
-
-
-
Available Capacity Calculation
> 0°C
NAC / “Full Reference”
-20°C < T < 0°C
0.75 * NAC / “Full Reference”
0
When charge rate falls below 2 counts/sec
< -20°C
0.5 * NAC / “Full Reference”
1
When charge rate is above 2 counts/sec
Where CR is:
The fast charge regime efficiency factors are used when
CR = 1. When CR = 0, the trickle charge efficiency factors are used. The time to change CR varies due to the
user-selectable count rates.
The adjustment between > 0°C and -20°C < T < 0°C has a
4°C hysteresis.
Nominal Available Charge Register (NAC)
The discharge rate flags, DR2–0, are bits 6–4.
The read/write NACH register (address=03h) and the
read-only NACL register (address=17h) are the main
gas gauging registers for the bq2011. The NAC registers
are incremented during charge actions and decremented
during discharge and self-discharge actions. The correction factors for charge/discharge efficiency are applied
automatically to NAC.
FLGS2 Bits
7
6
5
4
3
2
1
-
DR2
DR1
DR0
-
-
-
0
They are used to determine the present discharge regime as follows:
On reset, the NACH and NACL registers are cleared to
zero. NACL stops counting when NACH reaches zero.
When the bq2011 detects a valid charge, NACL resets to
zero; writing to the NAC register affects the available
charge counts and, therefore, affects the bq2011 gas
gauge operation.
DR2
DR1
DR0
VSR (V)
0
0
0
VSR < 50mV
0
0
1
50mV < VSR < 100mV
(overload, OVLD=1)
Battery Identification Register (BATID)
0
1
0
100mV < VSR < 150mV
The read/write BATID register (address=04h) is available for use by the system to determine the type of battery pack. The BATID contents are retained as long as
VCC is greater than 2V. The contents of BATID have no
effect on the operation of the bq2011. There is no default setting for this register.
0
1
1
150mV < VSR < 253mV
1
0
0
VSRD > 253mV
The overload flag (OVLD) is asserted when a discharge
overload is detected, VSRD > 50mV. OVLD remains asserted as long as the condition persists and is cleared
when VSRD < 50mV.
Last Measured Discharge Register (LMD)
LMD is a read/write register (address=05h) that the
bq2011 uses as a measured full reference. The bq2011
adjusts LMD based on the measured discharge capacity
of the battery from full to empty. In this way the bq2011
updates the capacity of the battery. LMD is set to PFC
during a bq2011 reset.
FLGS2 Bits
7
6
5
4
3
2
1
0
-
-
-
-
-
-
-
OVLD
DR2–0 and OVLD are set based on the measurement of the
voltage at the SR pin relative to VSS. The rate at which
this measurement is made varies with device activity.
Secondary Status Flags Register (FLGS2)
The read-only FLGS2 register (address=06h) contains
the secondary bq2011 flags.
The charge rate flag (CR) is used to denote the fast
charge regime. Fast charge is assumed whenever a
charge action is initiated. The CR flag remains asserted
if the charge rate does not fall below 2 counts/sec.
13
bq2011
Full Count Register (FULCNT)
Resetting the bq2011 sets the following:
The read-only FULCNT register (address=0bh) provides
the system with a diagnostic of the number of times the
battery has been fully charged (NAC = LMD). The
number of full occurrences can be determined by multiplying the value in the FULCNT register by 16. Any discharge action other than self-discharge allows detection of
another full occurrence during the next valid charge action.
n
LMD = PFC
n
CPI, VDQ, NAC, and OCE = 0 or
NAC = LMD when SEG5 = L
n
CI and BRP = 1
Display
The bq2011 can directly display capacity information
using low-power LEDs. If LEDs are used, the segment
pins should be tied to VCC, the battery, or the MODE pin
for programming the bq2011.
Capacity Inaccurate Count Register (CPI)
The read-only CPI register (address=09h) is used to indicate the number of times a battery has been charged
without an LMD update. Because the capacity of a rechargeable battery varies with age and operating conditions, the bq2011 adapts to the changing capacity over
time. A complete discharge from full (NAC=LMD) to
empty (EDV=1) is required to perform an LMD update
assuming there have been no intervening valid charges,
the temperature is greater than or equal to 0°C, and the
self-discharge counter is less than 4096 counts.
The bq2011 displays the battery charge state in either
absolute or relative mode. In relative mode, the battery
charge is represented as a percentage of the LMD. Each
LED segment represents 20% of the LMD.
In absolute mode, each segment represents a fixed
amount of charge, based on the initial PFC. In absolute
mode, each segment represents 20% of the PFC. As the
battery wears out over time, it is possible for the LMD
to be below the initial PFC. In this case, all of the LEDs
may not turn on, representing the reduction in the actual battery capacity.
The CPI register is incremented every time a valid
charge is detected. The register increments to 255 without rolling over. When the contents of CPI are incremented to 64, the capacity inaccurate flag, CI, is asserted in the FLGS1 register. CPI is reset whenever an
update of the LMD register is performed, and the CI flag
is also cleared.
The capacity display is also adjusted for the present battery temperature. The temperature adjustment reflects
the available capacity at a given temperature but does
not affect the NAC register. The temperature adjustments are detailed in the TMPGG register description.
Output Control Register (OCTL)
When DISP is tied to VCC, the SEG1–5 outputs are inactive. When DISP is left floating, the display becomes active during charge if the NAC registers are counting at a
rate equivalent to VSRO < -1mV or fast discharge if the
NAC registers are counting at a rate equivalent to VSRO
> 2mV. When pulled low, the segment output becomes
active for 4 seconds, ± 0.5 seconds.
The write-only OCTL register (address=0ah) provides
the system with a means to check the display connections for the bq2011. The segment drivers may be overwritten by data from OCTL when the least-significant
bit of OCTL, OCE, is set. The data in bits OC5–1 of the
OCTL register (see Table 4 on page 10 for details) is output onto the segment pins, SEG 5–1 , respectively if
OCE=1. Whenever OCE is written to 1, the MSB of
OCTL should be set to a 1. The OCE register location
must be cleared to return the bq2011 to normal operation. OCE may be cleared by either writing the bit to a
logic zero via the serial port or by resetting the bq2011
as explained below. Note: Whenever the OCTL register is
written, the MSB of OCTL should be written to a logic one.
The segment outputs are modulated as two banks, with
segments 1, 3, and 5 alternating with segments 2 and 4.
The segment outputs are modulated at approximately
320Hz, with each bank active for 30% of the period.
SEG1 blinks at a 4Hz rate whenever VSB has been detected to be below VEDV to indicate a low-battery condition or NAC is less than 10% of the LMD or PFC, depending on the display mode.
Reset Register (RST)
The reset register (address=39h) provides the means to
perform a software-controlled reset of the device. A full
device reset may be accomplished by first writing LMD
(address = 05h) to 00h and then writing the RST register contents from 00h to 80h. Setting any bit other than
the most-significant bit of the RST register is not allowed, and results in improper operation of the bq2011.
Microregulator
The bq2011 can operate directly from 4 cells. To facilitate
the power supply requirements of the bq2011, an REF output is provided to regulate an external low-threshold nFET. A micropower source for the bq2011 can be inexpensively built using the FET and an external resistor.
14
bq2011
Absolute Maximum Ratings
Symbol
Parameter
Minimum
Maximum
Unit
VCC
Relative to VSS
-0.3
+7.0
V
All other pins
Relative to VSS
-0.3
+7.0
V
VSR
Relative to VSS
TOPR
Operating temperature
Note:
Notes
-0.3
+7.0
V
Minimum 100Ω series resistor
should be used to protect SR in case
of a shorted battery (see the bq2011
application note for details).
0
+70
°C
Commercial
Permanent device damage may occur if Absolute Maximum Ratings are exceeded. Functional operation should be limited to the Recommended DC Operating Conditions detailed in this data sheet. Exposure to conditions beyond the operational limits for extended periods of time may affect device reliability.
DC Voltage Thresholds (TA = TOPR; V = 3.0 to 6.5V)
Symbol
Parameter
Minimum
Typical
Maximum
Unit
0.87
0.90
0.93
V
Notes
VEDV
End-of-discharge warning
VSR1
Discharge compensation threshold
20
50
75
mV
SR (see note)
VSR2
Discharge compensation threshold
70
100
125
mV
SR (see note)
VSR3
Discharge compensation threshold
120
150
175
mV
SR (see note)
VSR4
Discharge compensation threshold
220
253
275
mV
SR (see note)
VSRQ
Valid charge
-
-
-400
µV
VSR + VOS
VSRD
Valid discharge
500
-
-
µV
VSR + VOS
VMCV
Maximum single-cell voltage
1.95
2.0
2.05
V
SB
VBR
Battery removed/replaced
-
0.1
0.25
V
SB
Note:
SB
For proper operation of the threshold detection circuit, VCC must be at least 1.5V greater than the voltage being measured.
15
bq2011
DC Electrical Characteristics (TA = TOPR)
Symbol
Parameter
VCC
Supply voltage
VOS
Offset referred to VSR
VREF
RREF
Minimum
Typical
Maximum
Unit
Notes
3.0
4.25
6.5
V
VCC excursion from < 2.0V to ≥
3.0V initializes the unit.
-
±50
±150
µV
DISP = VCC
Reference at 25°C
5.7
6.0
6.3
V
IREF = 5µA
Reference at -40°C to +85°C
4.5
-
7.5
V
IREF = 5µA
Reference input impedance
2.0
5.0
-
MΩ
VREF = 3V
-
90
135
µA
VCC = 3.0V, DQ = 0
180
µA
VCC = 4.25V, DQ = 0
VCC = 6.5V, DQ = 0
ICC
Normal operation
-
120
-
170
250
µA
VSB
Battery input
0
-
VCC
V
RSBmax
SB input impedance
10
-
-
MΩ
0 < VSB < VCC
IDISP
DISP input leakage
-
-
5
µA
VDISP = VSS
IMODE
MODE input leakage
-0.2
-
0.2
µA
DISP = VCC
IRBI
RBI data-retention current
-
-
100
nA
VRBI > VCC < 3V
RDQ
Internal pulldown
500
-
-
KΩ
VSR
Sense resistor input
-0.3
-
2.0
V
RSR
SR input impedance
10
-
-
MΩ
VIHPFC
PFC logic input high
VCC - 0.2
-
-
V
VILPFC
PFC logic input low
VIZPFC
PFC logic input Z
IIHPFC
IILPFC
VSR > VSS = discharge;
VSR < VSS = charge
-200mV < VSR < VCC
PFC
-
-
VSS + 0.2
V
PFC
float
-
float
V
PFC
PFC input high current
-
1.2
-
µA
VPFC = VCC/2
PFC input low current
-
1.2
-
µA
VPFC = VCC/2
VOLSL
SEGX output low, low VCC
-
0.1
-
V
VCC = 3V, IOLS ≤ 1.75mA
SEG1–SEG5
VOLSH
SEGX output low, high VCC
-
0.4
-
V
VCC = 6.5V, IOLS ≤ 11.0mA
SEG1–SEG5
VOHML
MODE output high, low VCC
VCC - 0.3
-
-
V
VCC = 3V, IOHMODE = -5.25mA
VOHMH
MODE output high, high VCC
VCC - 0.6
-
-
V
VCC = 6.5V, IOHMODE = -33.0mA
IOHMODE MODE source current
-33
-
-
mA
At VOHMODE = VCC - 0.6V
IOLS
SEGX sink current
11.0
-
-
mA
At VOLSH = 0.4V, VCC = 6.5V
IOL
Open-drain sink current
5.0
-
-
mA
At VOL = VSS + 0.3V, DQ
VOL
Open-drain output low
-
-
0.5
V
IOL ≤ 5mA, DQ
VIHDQ
DQ input high
2.5
-
-
V
DQ
VILDQ
DQ input low
-
-
0.8
V
DQ
RFLOAT
Float state external impedance
-
5
-
MΩ
PFC
Note:
All voltages relative to VSS.
16
bq2011
Serial Communication Timing Specification (TA = TOPR)
Symbol
Parameter
Minimum
Typical
Maximum
Unit
tCYCH
Cycle time, host to bq2011
3
-
-
ms
tCYCB
Cycle time, bq2011 to host
3
-
6
ms
tSTRH
Start hold, host to bq2011
5
-
-
ns
tSTRB
Start hold, bq2011 to host
500
-
-
µs
tDSU
Data setup
-
-
750
µs
tDH
Data hold
750
-
-
µs
tDV
Data valid
1.50
-
-
ms
tSSU
Stop setup
-
-
2.25
ms
tSH
Stop hold
700
-
-
µs
tSV
Stop valid
2.95
-
-
ms
tB
Break
3
-
-
ms
tBR
Break recovery
1
-
-
ms
Note:
Notes
See note
The open-drain DQ pin should be pulled to at least VCC by the host system for proper DQ operation.
DQ may be left floating if the serial interface is not used.
Serial Communication Timing Illustration
DQ
(R/W "1")
DQ
(R/W "0")
tSTRH
tSTRB
tDH
tDSU
tDV
tSH
tSSU
DQ
(BREAK)
tSV
tCYCH, tCYCB, tB
17
tBR
bq2011
16-Pin SOIC Narrow (SN)
16-Pin SN (SOIC Narrow)
D
e
Dimension
Minimum
A
0.060
A1
0.004
B
0.013
C
0.007
D
0.385
E
0.150
e
0.045
H
0.225
L
0.015
All dimensions are in inches.
B
E
H
A
C
A1
.004
L
18
Maximum
0.070
0.010
0.020
0.010
0.400
0.160
0.055
0.245
0.035
bq2011
Data Sheet Revision History
Change No. Page No.
3
7
Description
Nature of Change
Self-discharge count rate
Was:
Is:
1
1
64
80
* NAC rate per day
* NAC rate per day
3
7
Compensation factor 30–40°C
Was:
Is:
0.90
0.95
3
7
Compensation factor >40°C
Was:
Is:
0.80
0.90
4
7
Charge compensation
Changed compensation factor variation with temperature
4
8
Self-discharge compensation
Changed self-discharge compensation rate variation with
temperature
Notes:
Changes 1 and 2 = See the 1995 Data Book.
Change 3 = Jan. 1996 D changes from July 1994 C.
Change 4 = Feb. 1996 E changes from Jan. 1996 D.
Ordering Information
bq2011
Temperature Range:
blank = Commercial (0 to +70°C)
Package Option:
SN = 16-pin narrow SOIC
Device:
bq2011 Gas Gauge IC
19
PACKAGE OPTION ADDENDUM
www.ti.com
8-Mar-2005
PACKAGING INFORMATION
Orderable Device
Status (1)
Package
Type
Package
Drawing
Pins Package Eco Plan (2)
Qty
Lead/Ball Finish
BQ2011SN-D118
ACTIVE
SOIC
D
16
48
None
CU NIPDAU
BQ2011SN-D118G4
PREVIEW
SOIC
D
16
48
None
Call TI
BQ2011SN-D118TR
ACTIVE
SOIC
D
16
2500
None
CU NIPDAU
MSL Peak Temp (3)
Level-1-220C-UNLIM
Call TI
Level-1-220C-UNLIM
(1)
The marketing status values are defined as follows:
ACTIVE: Product device recommended for new designs.
LIFEBUY: TI has announced that the device will be discontinued, and a lifetime-buy period is in effect.
NRND: Not recommended for new designs. Device is in production to support existing customers, but TI does not recommend using this part in
a new design.
PREVIEW: Device has been announced but is not in production. Samples may or may not be available.
OBSOLETE: TI has discontinued the production of the device.
(2)
Eco Plan - May not be currently available - please check http://www.ti.com/productcontent for the latest availability information and additional
product content details.
None: Not yet available Lead (Pb-Free).
Pb-Free (RoHS): TI's terms "Lead-Free" or "Pb-Free" mean semiconductor products that are compatible with the current RoHS requirements
for all 6 substances, including the requirement that lead not exceed 0.1% by weight in homogeneous materials. Where designed to be soldered
at high temperatures, TI Pb-Free products are suitable for use in specified lead-free processes.
Green (RoHS & no Sb/Br): TI defines "Green" to mean "Pb-Free" and in addition, uses package materials that do not contain halogens,
including bromine (Br) or antimony (Sb) above 0.1% of total product weight.
(3)
MSL, Peak Temp. -- The Moisture Sensitivity Level rating according to the JEDECindustry standard classifications, and peak solder
temperature.
Important Information and Disclaimer:The information provided on this page represents TI's knowledge and belief as of the date that it is
provided. TI bases its knowledge and belief on information provided by third parties, and makes no representation or warranty as to the
accuracy of such information. Efforts are underway to better integrate information from third parties. TI has taken and continues to take
reasonable steps to provide representative and accurate information but may not have conducted destructive testing or chemical analysis on
incoming materials and chemicals. TI and TI suppliers consider certain information to be proprietary, and thus CAS numbers and other limited
information may not be available for release.
In no event shall TI's liability arising out of such information exceed the total purchase price of the TI part(s) at issue in this document sold by TI
to Customer on an annual basis.
Addendum-Page 1
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