TI bq27541DRZT-G1

bq27541-G1
www.ti.com
SLUSAL6B – NOVEMBER 2011 – REVISED JUNE 2012
Single Cell Li-Ion Battery Fuel Gauge for Battery Pack Integration
: bq27541-G1
FEATURES
APPLICATIONS
•
•
•
•
•
•
1
23
•
•
•
•
•
Battery Fuel Gauge for 1-Series (1sXp) Li-Ion
Applications up to 32Ahr capacity
Microcontroller Peripheral Provides:
– Accurate Battery Fuel Gauging supports up
to 32Ahr
– Internal or External Temperature Sensor for
Battery Temperature Reporting
– SHA-1/HMAC Authentication
– Lifetime Data Logging
– 64 Bytes of Non-Volatile Scratch Pad
FLASH
Battery Fuel Gauging Based on Patented
Impedance Track™ Technology
– Models Battery Discharge Curve for
Accurate Time-To-Empty Predictions
– Automatically Adjusts for Battery Aging,
Battery Self-Discharge, and
Temperature/Rate Inefficiencies
– Low-Value Sense Resistor (5mΩ to 20mΩ)
Advanced Fuel Gauging Features
– Internal Short Detection
– Tab Disconnection Detection
HDQ and I2C™ Interface Formats for
Communication With Host System
Small 12-pin 2.5 mm × 4 mm SON Package
Smartphones
Tablets
Digital Still and Video Cameras
Handheld Terminals
MP3 or Multimedia Players
DESCRIPTION
The Texas Instruments bq27541-G1 Li-Ion battery
fuel gauge is a microcontroller peripheral that
provides fuel gauging for single-cell Li-Ion battery
packs.
The
device
requires
little
system
microcontroller firmware development for accurate
battery fuel gauging. The bq27541-G1 resides within
the battery pack or on the system’s main-board with
an embedded battery (nonremovable).
The bq27541-G1 uses the patented Impedance
Track™ algorithm for fuel gauging, and provides
information such as remaining battery capacity
(mAh), state-of-charge (%), run-time to empty (min.),
battery voltage (mV), and temperature (°C). It also
provides detections for internal short or tab
disconnection events.
The bq27541-G1 also features integrated support for
secure battery pack authentication, using the SHA1/HMAC authentication algorithm.
TYPICAL APPLICATION
Battery Pack
PACK+
Vcc
REGIN
LDO
REG25
BAT
SE
SHDQ
TS
bq27541
SDA
SCL
SRP
PROTECTION
IC
SRN
Vss
PACK-
1
2
3
Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of
Texas Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet.
Impedance Track is a trademark of Texas Instruments.
I2C is a trademark of NXP B.V Corporation.
PRODUCTION DATA information is current as of publication date.
Products conform to specifications per the terms of the Texas
Instruments standard warranty. Production processing does not
necessarily include testing of all parameters.
Copyright © 2011–2012, Texas Instruments Incorporated
bq27541-G1
SLUSAL6B – NOVEMBER 2011 – REVISED JUNE 2012
www.ti.com
These devices have limited built-in ESD protection. The leads should be shorted together or the device placed in conductive foam
during storage or handling to prevent electrostatic damage to the MOS gates.
DEVICE INFORMATION
AVAILABLE OPTIONS
PRODUCTION
PART NO. (1)
bq27541DRZR-G1
bq27541DRZT-G1
(1)
(2)
PACKAGE (2)
TA
COMMUNICATION
FORMAT
12-pin, 2.5-mm × 4-mm SON
–40°C to 85°C
I2C, HDQ (1)
TAPE AND REEL
QUANTITY
3000
250
2
bq27541-G1 is shipped in I C mode
For the most current package and ordering information, see the Package Option Addendum at the end of this document, or see the TI
website at www.ti.com.
bq27541 PIN DIAGRAM
(TOP VIEW)
SE
1
12
HDQ
REG25
2
11
SCL
REGIN
3
10
SDA
BAT
4
9
TS
VCC
5
8
SRN
VSS
6
7
SRP
bq27541
PIN FUNCTIONS
PIN
NAME
NO.
TYPE (1)
DESCRIPTION
BAT
4
I
Cell-voltage measurement input. ADC input. Decouple with 0.1μF capacitor.
REG25
2
P
2.5V output voltage of the internal integrated LDO. Connect a minimum 0.47μF ceramic capacitor.
REGIN
3
P
The input voltage for the internal integrated LDO. Connect a 0.1μF ceramic capacitor.
SCL
11
I
Slave I2C serial communications clock input line for communication with system (Slave). Open-drain I/O.
Use with 10kΩ pull-up resistor (typical).
SDA
10
I/O
Slave I2C serial communications data line for communication with system (Slave). Open-drain I/O. Use
with 10kΩ pull-up resistor (typical).
SE
1
O
Shutdown Enable output. Push-pull output. Leave Floating when it is not used.
HDQ
12
I/O
HDQ serial communications line (Slave). Open-drain. Use with 10kΩ pull-up resistor (typical) or leave
floating when it is not used.
SRN
8
IA
Analog input pin connected to the internal coulomb counter with a Kelvin connection where SRN is
nearest the PACK- connection. Connect to 5-mΩ to 20-mΩ sense resistor.
SRP
7
IA
Analog input pin connected to the internal coulomb counter with a Kelvin connection where SRP is
nearest the CELL- connection. Connect to 5-mΩ to 20-mΩ sense resistor
TS
9
IA
Pack thermistor voltage sense (use 103AT-type thermistor). ADC input
Vcc
5
P
Processor power input. The minimum 0.47μF capacitor connected to REG25 should be close to Vcc.
Vss
6
P
Device ground
(1)
2
I/O = Digital input/output, IA = Analog input, P = Power connection
Copyright © 2011–2012, Texas Instruments Incorporated
bq27541-G1
www.ti.com
SLUSAL6B – NOVEMBER 2011 – REVISED JUNE 2012
ELECTRICAL SPECIFICATIONS
ABSOLUTE MAXIMUM RATINGS
over operating free-air temperature range (unless otherwise noted) (1)
VALUE
MIN
UNIT
MAX
VI
Regulator input, REGIN
–0.3
24
V
VCC
Supply voltage range
–0.3
2.75
V
VIOD
Open-drain I/O pins (SDA, SCL, HDQ)
–0.3
6
V
VBAT
BAT input, (pin 4)
–0.3
6
V
VI
Input voltage range to all others (pins 1, 7, 8, 9)
–0.3
VCC + 0.3
V
ESD
Human Body Model (HBM), BAT pin
1.5
Human Body Model (HBM), all pins
2
TF
Functional temperature range
–40
100
Tstg
Storage temperature range
–65
150
(1)
kV
°C
Stresses beyond those listed under absolute maximum ratings may cause permanent damage to the device. These are stress ratings
only, and functional operation of the device at these or any other conditions beyond those indicated under recommended operating
conditions is not implied. Exposure to absolute-maximum-rated conditions for extended periods may affect device reliability.
THERMAL INFORMATION
THERMAL METRIC (1)
bq27541-G1
DRZ (12-PINS)
θJA
Junction-to-ambient thermal resistance
64.1
θJCtop
Junction-to-case (top) thermal resistance
59.8
θJB
Junction-to-board thermal resistance
52.7
ψJT
Junction-to-top characterization parameter
0.3
ψJB
Junction-to-board characterization parameter
28.3
θJCbot
Junction-to-case (bottom) thermal resistance
2.4
UNITS
°C/W
space
(1)
For more information about traditional and new thermal metrics, see the IC Package Thermal Metrics application report, SPRA953.
RECOMMENDED OPERATING CONDITIONS
TA = -40°C to 85°C; typical values at TA = 25°C and V(REGIN) = VBAT = 3.6 V (unless otherwise noted)
MIN
No operating restrictions
VI
Supply voltage, REGIN
ICC
Normal operating mode current
I(SLP)
Low-power operating mode current (1)
No FLASH writes
I(FULLSLP) Low-power operating mode current (1)
(1)
MAX
5.5
2.45
2.7
Fuel gauge in NORMAL mode.
ILOAD > Sleep Current
(1)
TYP
2.7
UNIT
V
131
μA
Fuel gauge in SLEEP mode.
ILOAD < Sleep Current
60
μA
Fuel gauge in FULLSLEEP mode.
ILOAD < Sleep Current
21
μA
Fuel gauge in HIBERNATE mode.
Available in I2C Mode only.
ILOAD < Hibernate Current
6
μA
I(HIB)
Hibernate operating mode current
VOL
Output voltage low (HDQ, SDA, SCL, SE) IOL = 3 mA
VOH(PP)
Output high voltage (SE)
IOH = –1 mA
VCC–0.5
V
VOH(OD)
Output high voltage (HDQ, SDA, SCL)
External pull-up resistor connected to VCC
VCC–0.5
V
VIL
Input voltage low (HDQ, SDA, SCL)
–0.3
0.6
V
VIH
Input voltage high (HDQ, SDA, SCL)
1.2
6
V
(1)
0.4
V
Specified by design. Not tested in production.
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RECOMMENDED OPERATING CONDITIONS (continued)
TA = -40°C to 85°C; typical values at TA = 25°C and V(REGIN) = VBAT = 3.6 V (unless otherwise noted)
MIN
TYP
MAX
UNIT
V(A1)
Input voltage range (TS)
VSS–0.125
2
V
V(A2)
Input voltage range (BAT)
VSS–0.125
5
V
V(A3)
Input voltage range (SRP, SRN)
VSS–0.125
0.125
V
Ilkg
Input leakage current (I/O pins)
0.3
μA
tPUCD
Power-up communication delay
250
ms
POWER-ON RESET
TA = –40°C to 85°C, C(REG) = 0.47μF, 2.45 V < V(REGIN) = VBAT < 5.5 V; typical values at TA = 25°C and V(REGIN) = VBAT = 3.6 V
(unless otherwise noted)
PARAMETER
TEST CONDITIONS
VIT+
Positive-going battery voltage input at VCC
VHYS
Power-on reset hysteresis
MIN
TYP
MAX
UNIT
2.05
2.20
2.31
V
45
115
185
mV
2.5 V LDO REGULATOR (1)
TA = –40°C to 85°C, C(REG) = 0.47 μF, 2.45 V < V(REGIN) = VBAT < 5.5 V; typical values at TA = 25°C and V(REGIN) = VBAT = 3.6 V
(unless otherwise noted)
PARAMETER
VO
Regulator output voltage, REG25
TEST CONDITION
2.7 V ≤ V(REGIN) ≤ 5.5 V,
IOUT ≤ 16mA
2.45 V ≤ V(REGIN) < 2.7 V (low
battery), IOUT ≤ 3mA
2.7 V, IOUT ≤ 16 mA
MIN
TYP
MAX
2.4
2.5
2.6
2.4
V
280
Regulator dropout voltage
ΔV(REGTEMP)
Regulator output change with
temperature
V(REGIN) = 3.6 V,
IOUT = 16 mA
ΔV(REGLINE)
Line regulation
2.7 V ≤ V(REGIN) ≤ 5.5 V, IOUT = 16 mA
11
25
0.2 mA ≤ IOUT ≤ 3 mA, V(REGIN) = 2.45 V
34
40
3 mA ≤ IOUT ≤ 16 mA, V(REGIN) = 2.7 V
31
ΔV(REGLOAD) Load regulation
IOS
(1)
(2)
(2)
Short circuit current limit
V(REG25) = 0 V
V
TA = –40°C to 85°C
VDO
2.45 V, IOUT ≤ 3 mA
UNIT
TA = –40°C to 85°C
50
TA = –40°C to 85°C
mV
0.3%
TA = –40°C to 85°C
250
mV
mV
mA
LDO output current, IOUT, is the total load current. LDO regulator should be used to power internal fuel gauge only.
Specified by design. Not production tested.
INTERNAL TEMPERATURE SENSOR CHARACTERISTICS
TA = –40°C to 85°C, C(REG) = 0.47μF, 2.45 V < V(REGIN) = VBAT < 5.5 V; typical values at TA = 25°C and V(REGIN) = VBAT = 3.6 V
(unless otherwise noted)
PARAMETER
G(TEMP)
4
TEST CONDITIONS
Temperature sensor voltage gain
MIN
TYP
–2.0
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MAX
UNIT
mV/°C
Copyright © 2011–2012, Texas Instruments Incorporated
Product Folder Link(s): bq27541-G1
bq27541-G1
www.ti.com
SLUSAL6B – NOVEMBER 2011 – REVISED JUNE 2012
HIGH FREQUENCY OSCILLATOR
TA = –40°C to 85°C, C(REG) = 0.47μF, 2.45 V < V(REGIN) = VBAT < 5.5 V; typical values at TA = 25°C and V(REGIN) = VBAT = 3.6 V
(unless otherwise noted)
PARAMETER
f(OSC)
Operating frequency
f(EIO)
Frequency error (1)
t(SXO)
(1)
(2)
(3)
TEST CONDITIONS
MIN
TYP
MAX
UNIT
2.097
(2)
MHz
TA = 0°C to 60°C
–2.0%
0.38%
2.0%
TA = –20°C to 70°C
–3.0%
0.38%
3.0%
TA = –40°C to 85°C
-4.5%
0.38%
4.5%
2.5
5
Start-up time (3)
ms
The frequency error is measured from 2.097 MHz.
The frequency drift is included and measured from the trimmed frequency at VCC = 2.5 V, TA = 25°C.
The startup time is defined as the time it takes for the oscillator output frequency to be ±3%.
LOW FREQUENCY OSCILLATOR
TA = –40°C to 85°C, C(REG) = 0.47μF, 2.45 V < V(REGIN) = VBAT < 5.5 V; typical values at TA = 25°C and V(REGIN) = VBAT = 3.6 V
(unless otherwise noted)
PARAMETER
f(LOSC)
f(LEIO)
Frequency error (1)
t(LSXO)
Start-up time (3)
(1)
(2)
(3)
TEST CONDITIONS
MIN
TYP
Operating frequency
MAX
32.768
(2)
UNIT
KHz
TA = 0°C to 60°C
–1.5%
0.25%
1.5%
TA = –20°C to 70°C
–2.5%
0.25%
2.5%
TA = –40°C to 85°C
-4.0%
0.25%
4.0%
500
μs
The frequency drift is included and measured from the trimmed frequency at VCC = 2.5 V, TA = 25°C.
The frequency error is measured from 32.768 KHz.
The startup time is defined as the time it takes for the oscillator output frequency to be ±3% of typical oscillator frequency.
INTEGRATING ADC (COULOMB COUNTER) CHARACTERISTICS
TA = –40°C to 85°C, C(REG) = 0.47μF, 2.45 V < V(REGIN) = VBAT < 5.5 V; typical values at TA = 25°C and V(REGIN) = VBAT = 3.6 V
(unless otherwise noted)
PARAMETER
TEST CONDITIONS
VIN(SR)
Input voltage range, V(SRN) and V(SRP)
VSR = V(SRN) – V(SRP)
tCONV(SR)
Conversion time
Single conversion
Resolution
VOS(SR)
Input offset
INL
Integral nonlinearity error
ZIN(SR)
Effective input resistance (1)
Ilkg(SR)
Input leakage current (1)
(1)
MIN
TYP
–0.125
MAX
UNIT
0.125
V
1
14
s
15
μV
10
±0.007
bits
±0.034
2.5
FSR
MΩ
0.3
μA
Specified by design. Not production tested.
ADC (TEMPERATURE AND CELL VOLTAGE) CHARACTERISTICS
TA = –40°C to 85°C, C(REG) = 0.47μF, 2.45 V < V(REGIN) = VBAT < 5.5 V; typical values at TA = 25°C and V(REGIN) = VBAT = 3.6 V
(unless otherwise noted)
PARAMETER
VIN(ADC)
Input voltage range
tCONV(ADC)
Conversion time
TEST CONDITIONS
Resolution
TYP
Input offset
Z(ADC1)
Effective input resistance (TS)
Z(ADC2)
Effective input resistance (BAT) (1)
MAX
1
14
VOS(ADC)
(1)
MIN
–0.2
ms
15
bits
8
bq27541-G1 not measuring cell voltage
bq27541-G1 measuring cell voltage
V
125
1
(1)
UNIT
mV
MΩ
8
MΩ
100
kΩ
Specified by design. Not production tested.
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ADC (TEMPERATURE AND CELL VOLTAGE) CHARACTERISTICS (continued)
TA = –40°C to 85°C, C(REG) = 0.47μF, 2.45 V < V(REGIN) = VBAT < 5.5 V; typical values at TA = 25°C and V(REGIN) = VBAT = 3.6 V
(unless otherwise noted)
PARAMETER
TEST CONDITIONS
MIN
TYP
Input leakage current (1)
Ilkg(ADC)
MAX
0.3
UNIT
μA
DATA FLASH MEMORY CHARACTERISTICS
TA = –40°C to 85°C, C(REG) = 0.47μF, 2.45 V < V(REGIN) = VBAT < 5.5 V; typical values at TA = 25°C and V(REGIN) = VBAT = 3.6 V
(unless otherwise noted)
PARAMETER
TEST CONDITIONS
Flash programming write-cycles
(1)
TYP
Word programming time
ICCPROG
Flash-write supply current (1)
MAX
UNIT
10
Years
20,000
Cycles
(1)
tWORDPROG
(1)
MIN
Data retention (1)
tDR
5
2
ms
10
mA
Specified by design. Not production tested.
HDQ COMMUNICATION TIMING CHARACTERISTICS
TA = –40°C to 85°C, CREG = 0.47μF, 2.45 V < VREGIN = VBAT < 5.5 V; typical values at TA = 25°C and VREGIN = VBAT = 3.6 V
(unless otherwise noted)
PARAMETER
TEST CONDITIONS
MIN
TYP
MAX
UNIT
205
250
μs
50
μs
μs
t(CYCH)
Cycle time, host to bq27541-G1
190
t(CYCD)
Cycle time, bq27541-G1 to host
190
t(HW1)
Host sends 1 to bq27541-G1
0.5
t(DW1)
bq27541-G1 sends 1 to host
32
50
μs
t(HW0)
Host sends 0 to bq27541-G1
86
145
μs
t(DW0)
bq27541-G1 sends 0 to host
80
145
μs
t(RSPS)
Response time, bq27541-G1 to host
190
950
μs
t(B)
Break time
190
t(BR)
Break recovery time
t(RISE)
HDQ line rising time to logic 1 (1.2V)
μs
μs
40
950
ns
1.2V
t(BR)
t(B)
t(RISE)
(b) HDQ line rise time
(a) Break and Break Recovery
t(DW1)
t(HW1)
t(DW0)
t(CYCD)
t(HW0)
t(CYCH)
(d) Gauge Transmitted Bit
(c) Host Transmitted Bit
Break
7-bit address
1-bit
R/W
8-bit data
t(RSPS)
(e) Gauge to Host Response
Figure 1. Timing Diagrams
6
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I2C-COMPATIBLE INTERFACE TIMING CHARACTERISTICS
TA = –40°C to 85°C, CREG = 0.47μF, 2.45 V < VREGIN = VBAT < 5.5 V; typical values at TA = 25°C and VREGIN = VBAT = 3.6 V
(unless otherwise noted)
PARAMETER
TEST CONDITIONS
MIN
TYP
MAX
UNIT
300
ns
300
ns
tr
SCL/SDA rise time
tf
SCL/SDA fall time
tw(H)
SCL pulse width (high)
600
ns
tw(L)
SCL pulse width (low)
1.3
μs
tsu(STA)
Setup for repeated start
600
ns
td(STA)
Start to first falling edge of SCL
tsu(DAT)
Data setup time
th(DAT)
Data hold time
tsu(STOP)
Setup time for stop
tBUF
Bus free time between stop and start
fSCL
Clock frequency
600
ns
1000
ns
0
ns
600
ns
66
μs
400
tSU(STA)
tw(H)
tf
tw(L)
tr
kHz
t(BUF)
SCL
SDA
td(STA)
tsu(STOP)
tf
tr
th(DAT)
tsu(DAT)
REPEATED
START
STOP
START
Figure 2. I2C-Compatible Interface Timing Diagrams
GENERAL DESCRIPTION
The bq27541-G1 accurately predicts the battery capacity and other operational characteristics of a single Libased rechargeable cell. It can be interrogated by a system processor to provide cell information, such as stateof-charge (SOC) and time-to-empty (TTE).
Information is accessed through a series of commands, called Standard Commands. Further capabilities are
provided by the additional Extended Commands set. Both sets of commands, indicated by the general format
Command( ), are used to read and write information contained within the bq27541-G1 control and status
registers, as well as its data flash locations. Commands are sent from system to gauge using the bq27541-G1
serial communications engine, and can be executed during application development, pack manufacture, or endequipment operation.
Cell information is stored in the bq27541-G1 in non-volatile flash memory. Many of these data flash locations are
accessible during application development. They cannot, generally, be accessed directly during end-equipment
operation. Access to these locations is achieved by either use of the bq27541-G1 companion evaluation
software, through individual commands, or through a sequence of data-flash-access commands. To access a
desired data flash location, the correct data flash subclass and offset must be known.
The bq27541-G1 provides 64 bytes of user-programmable data flash memory, partitioned into two (2) 32-byte
blocks: Manufacturer Info Block A and Manufacturer Info Block B. This data space is accessed through a
data flash interface. For specifics on accessing the data flash, see section Manufacturer Information Blocks. The
key to the bq27541-G1 high-accuracy gas gauging prediction is Texas Instrument’s proprietary Impedance
Track™ algorithm. This algorithm uses cell measurements, characteristics, and properties to create state-ofcharge predictions that can achieve less than 1% error across a wide variety of operating conditions and over the
lifetime of the battery.
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The bq27541-G1 measures charge/discharge activity by monitoring the voltage across a small-value series
sense resistor (5 mΩ to 20 mΩ typ.) located between the CELL-and the battery’s PACK-terminal. When a cell is
attached to the bq27541-G1, cell impedance is learned, based on cell current, cell open-circuit voltage (OCV),
and cell voltage under loading conditions.
The bq27541-G1 external temperature sensing is optimized with the use of a high accuracy negative
temperature coefficient (NTC) thermistor with R25 = 10kΩ ± 1% and B25/85 = 3435kΩ ± 1% (such as Semitec
103AT) for measurement. The bq27541-G1 can also be configured to use its internal temperature sensor. The
bq27541-G1 uses temperature to monitor the battery-pack environment, which is used for fuel gauging and cell
protection functionality.
To minimize power consumption, the bq27541-G1 has different power modes: NORMAL, SLEEP, FULLSLEEP,
and HIBERNATE. The bq27541-G1 passes automatically between these modes, depending upon the occurrence
of specific events, though a system processor can initiate some of these modes directly. More details can be
found in section Power Modes.
NOTE
FORMATTING CONVENTIONS IN THIS DOCUMENT:
Commands: italics with parentheses( ) and no breaking spaces. e.g. RemainingCapacity( )
Data Flash: italics, bold, and breaking spaces. e.g. Design Capacity
Register bits and flags: italics with brackets[ ]. e.g. [TDA]
Data flash bits: italics, bold, and brackets[ ]. e.g: [LED1]
Modes and states: ALL CAPITALS. e.g. UNSEALED mode
do not delete this subsection
8
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DATA COMMANDS
STANDARD DATA COMMANDS
The bq27541-G1 uses a series of 2-byte standard commands to enable system reading and writing of battery
information. Each standard command has an associated command-code pair, as indicated in Table 1. Each
protocol has specific means to access the data at each Command Code. DataRAM is updated and read by the
gauge only once per second. Standard commands are accessible in NORMAL operation mode.
Table 1. Standard Commands
COMMAND CODE
UNITS
SEALED
ACCESS
CNTL
0x00 / 0x01
N/A
R/W
NAME
Control( )
AtRate( )
AR
0x02 / 0x03
mA
R/W
UnfilteredSOC()
UFSOC
0x04 / 0x05
%
R
Temperature( )
TEMP
0x06 / 0x07
0.1K
R
Voltage( )
VOLT
0x08 / 0x09
mV
R
Flags( )
FLAGS
0x0a / 0x0b
N/A
R
NomAvailableCapacity( )
NAC
0x0c / 0x0d
mAh
R
FullAvailableCapacity( )
FAC
0x0e / 0x0f
mAh
R
RemainingCapacity( )
RM
0x10 / 0x11
mAh
R
FullChargeCapacity( )
FCC
0x12 / 0x13
mAh
R
AI
0x14 / 0x15
mA
R
AverageCurrent( )
TimeToEmpty( )
FilteredFCC()
StandbyCurrent( )
UnfilteredFCC()
MaxLoadCurrent( )
UnfilteredRM()
FilteredRM()
AveragePower( )
TTE
0x16 / 0x17
Minutes
R
FFCC
0x18 / 0x19
mAh
R
SI
0x1a / 0x1b
mA
R
UFFCC
0x1c / 0x1d
mAh
R
MLI
0x1e / 0x1f
mA
R
UFRM
0x20 / 0x21
mAh
R
FRM
0x22 / 0x23
mAh
R
AP
0x24 / 0x25
mW / cW
R
INTTEMP
0x28 / 0x29
0.1°K
R
CC
0x2a / 0x2b
Counts
R
StateOfCharge( )
SOC
0x2c / 0x2d
%
R
StateOfHealth( )
SOH
0x2e / 0x2f
% / num
R
PassedCharge( )
PCHG
0x34 / 0x35
mAh
R
DOD0( )
DOD0
0x36 / 0x37
HEX#
R
SelfDischargeCurrent()
SDSG
0x38 / 0x39
mA
R
InternalTemperature( )
CycleCount( )
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Control( ): 0x00/0x01
Issuing a Control( ) command requires a subsequent 2-byte subcommand. These additional bytes specify the
particular control function desired. The Control( ) command allows the system to control specific features of the
bq27541-G1 during normal operation and additional features when the bq27541-G1 is in different access modes,
as described in Table 2.
Table 2. Control( ) Subcommands
CNTL DATA
SEALED
ACCESS
CONTROL_STATUS
0x0000
Yes
Reports the status of DF Checksum, Hibernate, IT, etc.
DEVICE_TYPE
0x0001
Yes
Reports the device type of 0x0541 (indicating bq27541-G1)
FW_VERSION
0x0002
Yes
Reports the firmware version on the device type
HW_VERSION
0x0003
Yes
Reports the hardware version of the device type
Reserved
0x0004
No
Not to be used
RESET_DATA
0x0005
No
Returns reset data
Reserved
0x0006
No
Not to be used
PREV_MACWRITE
0x0007
No
Returns previous Control() subcommand code
CHEM_ID
0x0008
Yes
Reports the chemical identifier of the Impedance Track™ configuration
BOARD_OFFSET
0x0009
No
Forces the device to measure and store the board offset
CC_OFFSET
0x000A
No
Forces the device to measure internal CC offset
CNTL FUNCTION
DESCRIPTION
CC_OFFSET_SAVE
0x000B
No
Forces the device to store the internal CC offset
DF_VERSION
0x000C
Yes
Reports the data flash version on the device
SET_FULLSLEEP
0x0010
No
Set the [FullSleep] bit in Control Status register to 1
SET_HIBERNATE
0x0011
Yes
Forces CONTROL_STATUS [HIBERNATE] to 1
CLEAR_HIBERNATE
0x0012
Yes
Forces CONTROL_STATUS [HIBERNATE] to 0
SET_SHUTDOWN
0x0013
Yes
Enables the SE pin to change state
CLEAR_SHUTDOWN
0x0014
Yes
Disables the SE pin from changing state
SET_HDQINTEN
0x0015
Yes
Forces CONTROL_STATUS [HDQIntEn] to 1
CLEAR_HDQINTEN
0x0016
Yes
Forces CONTROL_STATUS [HDQIntEn] to 0
STATIC_CHEM_CHKSUM
0x0017
Yes
Calculates chemistry checksum
SEALED
0x0020
No
Places the bq27541-G1 in SEALED access mode
IT_ENABLE
0x0021
No
Enables the Impedance Track™ algorithm
CAL_ENABLE
0x002d
No
Toggle bq27541-G1 calibration mode
RESET
0x0041
No
Forces a full reset of the bq27541-G1
EXIT_CAL
0x0080
No
Exit bq27541-G1 calibration mode
ENTER_CAL
0x0081
No
Enter bq27541-G1 calibration mode
OFFSET_CAL
0x0082
No
Reports internal CC offset in calibration mode
10
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CONTROL_STATUS: 0x0000
Instructs the fuel gauge to return status information to Control addresses 0x00/0x01. The status word includes
the following information.
Table 3. CONTROL_STATUS Flags
bit7
bit6
bit5
bit4
bit3
bit2
bit1
bit0
High Byte
SE
FAS
SS
CALMODE
CCA
BCA
CSV
HDQHOSTIN
Low Byte
SHUTDWN
HIBERNATE
FULLSLEEP
SLEEP
LDMD
RUP_DIS
VOK
QEN
SE = Status bit indicating the SE pin is active. True when set. Default is 0.
FAS = Status bit indicating the bq27541-G1 is in FULL ACCESS SEALED state. Active when set.
SS = Status bit indicating the bq27541-G1 is in the SEALED State. Active when set.
CALMODE = Status bit indicating the calibration function is active. True when set. Default is 0.
CCA =
Status bit indicating the bq27541-G1 Coulomb Counter Calibration routine is active. The CCA routine will take place
approximately 1 minute after the initialization and periodically as gauging conditions change. Active when set.
BCA = Status bit indicating the bq27541-G1 Board Calibration routine is active. Active when set.
CSV = Status bit indicating a valid data flash checksum has been generated. Active when set.
HDQHOSTIN = Status bit indicating the HDQ interrupt function is active. True when set. Default is 0.
SHUTDWN = Control bit indicating the fuel gauge can force its SE pin low to signal an external shutdown. True when set. Default is 1
which is controlled by Pack Configuration Register.
HIBERNATE = Status bit indicating a request for entry into HIBERNATE from SLEEP mode has been issued. True when set. Default is
0.
FULLSLEEP =
Status bit indicating the bq27541-G1 is in FULLSLEEP mode. True when set. The state can be detected by monitoring
the power used by the bq27541-G1 because any communication will automatically clear it.
SLEEP = Status bit indicating the bq27541-G1 is in SLEEP mode. True when set.
LDMD = Status bit indicating the bq27541-G1 Impedance Track™ algorithm is using constant-power mode. True when set.
Default is 0 (constant-current mode).
RUP_DIS = Status bit indicating the bq27541-G1 Ra table updates are disabled. True when set.
VOK = Status bit indicating cell voltages are OK for Qmax updates. True when set.
QEN = Status bit indicating the bq27541-G1 Qmax updates are enabled. True when set.
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DEVICE_TYPE: 0x0001
Instructs the fuel gauge to return the device type to addresses 0x00/0x01. The bq27541-G1 device type returns
0x0541.
FW_VERSION: 0x0002
Instructs the fuel gauge to return the firmware version to addresses 0x00/0x01. The bq27541-G1 firmware
version returns 0x0222.
HW_VERSION: 0x0003
Instructs the fuel gauge to return the hardware version to addresses 0x00/0x01. For bq27541-G1, 0x0000 or
0x0060 is returned.
RESET_DATA: 0x0005
Instructs the fuel gauge to return the number of resets performed to addresses 0x00/0x01.
PREV_MACWRITE: 0x0007
Instructs the fuel gauge to return the previous Control() subcommand written to addresses 0x00/0x01. The value
returned is limited to less than 0x0020.
CHEM_ID: 0x0008
Instructs the fuel gauge to return the chemical identifier for the Impedance Track™ configuration to addresses
0x00/0x01.
BOARD_OFFSET: 0x0009
Instructs the fuel gauge to perform board offset calibraton. During board offset calibration the [BCA] bit is set
CC_OFFSET: 0x000A
Instructs the fuel gauge to perform coulomb counter offset calibration. During calibration the [CCA] bit is set
CC_OFFSET_SAVE: 0x000B
Instructs the fuel gauge to save calibration coulomb counter offset after calibration.
DF_VERSION: 0x000C
Instructs the gas gauge to return the data flash version stored in DF Config Version to addresses 0x00/0x01.
SET_FULLSLEEP: 0x0010
Instructs the gas gauge to set the FullSleep bit in Control Status register to 1. This will allow the gauge to enter
the FULLSLEEP power mode after the transition to SLEEP power state is detected. In FullSleep mode less
power is consumed by disabling an oscillator circuit used by the communication engines. For HDQ
communication one host message will be dropped. For I2C communications the first I2C message will incur a 6–8
millisecond clock stretch while the oscillator is started and stabilized. A communication to the device in
FULLSLEEP will force the part back to the SLEEP mode.
SET_HIBERNATE: 0x0011
Instructs the fuel gauge to force the CONTROL_STATUS [HIBERNATE] bit to 1. This will allow the gauge to
enter the HIBERNATE power mode after the transition to SLEEP power state is detected and the required
conditions are met. The [HIBERNATE] bit is automatically cleared upon exiting from HIBERNATE mode.
Note: The HIBERNATE mode is only available in I2C mode and is disabled when HDQ mode is used.
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CLEAR_HIBERNATE: 0x0012
Instructs the fuel gauge to force the CONTROL_STATUS [HIBERNATE] bit to 0. This will prevent the gauge from
entering the HIBERNATE power mode after the transition to SLEEP power state is detected unless Voltage() is
less than Hibernate V. It can also be used to force the gauge out of HIBERNATE mode.
SET_SHUTDOWN: 0x0013
Sets the CONTROL_STATUS [SHUTDWN] bit to 1, thereby enabling the SE pin to change state. The Impedance
Track algorithm controls the setting of the SE pin, depending on whether the conditions are met for fuel gauge
shutdown or not.
CLEAR_SHUTDOWN: 0x0014
Disables the SE pin from changing state. The SE pin is left in a high-impedance state.
SET_HDQINTEN: 0x0015
Instructs the fuel gauge to set the CONTROL_STATUS [HDQIntEn] bit to 1. This will enable the HDQ Interrupt
function. When this subcommand is received, the device will detect any of the interrupt conditions and assert the
interrupt at one second intervals until the CLEAR_HDQINTEN command is received or the count of
HDQHostIntrTries has lapsed (default 3).
CLEAR_HDQINTEN: 0x0016
Instructs the fuel gauge to set the CONTROL_STATUS [HDQIntEn] bit to 0. This will disable the HDQ Interrupt
function.
STATIC_CHEM_DF_CHKSUM: 0x0017
Instructs the fuel gauge to calculate chemistry checksum as a 16-bit unsigned integer sum of all static chemistry
data. The most significant bit (MSB) of the checksum is masked yielding a 15-bit checksum. This checksum is
compared with value stored in the data flash Static Chem DF Checksum. If the value matches, the MSB will be
cleared to indicate pass. If it does not match, the MSB will be set to indicate failure. The checksum can be used
to verify the integrity of the chemistry data stored internally.
SEALED: 0x0020
Instructs the gas gauge to transition from UNSEALED state to SEALED state. The gas gauge should always be
set to SEALED state for use in customer’s end equipment as it prevents spurious writes to most Standard
Commands and blocks access to most data flash.
IT ENABLE: 0x0021
This command forces the fuel gauge to begin the Impedance Track™ algorithm, sets bit 2 of UpdateStatus and
causes the [VOK] and [QEN] flags to be set in the CONTROL_STATUS register. [VOK] is cleared if the voltages
are not suitable for a Qmax update. Once set, [QEN] cannot be cleared. This command is only available when
the fuel gauge is UNSEALED and is typically enabled at the last step of production after system test is
completed.
RESET: 0x0041
This command instructs the gas gauge to perform a full reset. This command is only available when the gas
gauge is UNSEALED.
EXIT_CAL: 0x0080
This command instructs the gas gauge to exit calibration mode.
ENTER_CAL: 0x0081
This command instructs the gas gauge to enter calibration mode.
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OFFSET_CAL: 0x0082
This command instructs the gas gauge to perform offset calibration.
AtRate( ): 0x02/0x03
The AtRate( ) read-/write-word function is the first half of a two-function command call-set used to set the AtRate
value used in calculations made by the AtRateTimeToEmpty( ) function. The AtRate( ) units are in mA.
The AtRate( ) value is a signed integer, with negative values interpreted as a discharge current value. The
AtRateTimeToEmpty( ) function returns the predicted operating time at the AtRate value of discharge. The
default value for AtRate( ) is zero and will force AtRateTimeToEmpty( ) to return 65,535. Both the AtRate( ) and
AtRateTimeToEmpty( ) commands should only be used in NORMAL mode.
UnfilteredSOC( ): 0x04/0x05
This read-only function returns an unsigned integer value of the predicted remaining battery capacity expressed
as a percentage of UnfilteredFCC(), with a range of 0 to 100%.
Temperature( ): 0x06/0x07
This read-only function returns an unsigned integer value of the battery temperature in units of 0.1K measured by
the fuel gauge and is used for fuel gauging algorithm. It reports either the InternalTemperature() or the external
thermistor temperature depending on the setting of [TEMPS] bit in Pack Configuration.
Voltage( ): 0x08/0x09
This read-only function returns an unsigned integer value of the measured cell-pack voltage in mV with a range
of 0 to 6000 mV.
Flags( ): 0x0a/0x0b
This read-only function returns the contents of the gas-gauge status register, depicting the current operating
status.
Table 4. Flags Bit Definitions
bit7
bit6
bit5
bit4
bit3
bit2
bit1
bit0
High Byte
OTC
OTD
BATHI
BATLOW
CHG_INH
Low Byte
OCVTAKEN
ISD
TDD
HW1
HW0
RSVD
FC
CHG
SOC1
SOCF
DSG
OTC =
Over-Temperature in Charge condition is detected. True when set. Refer to the Data Flash Safety Subclass
parameters for threshold settings.
OTD =
Over-Temperature in Discharge condition is detected. True when set. Refer to the Data Flash Safety Subclass
parameters for threshold settings.
BATHI =
BATLOW =
Battery High bit indicating a high battery voltage condition. Refer to the Data Flash BATTERY HIGH parameters for
threshold settings.
Battery Low bit indicating a low battery voltage condition. Refer to the Data Flash BATTERY LOW parameters for
threshold settings.
CHG_INH = Charge Inhibit indicates the temperature is outside the range [Charge Inhibit Temp Low, Charge Inhibit Temp
High]. True when set.
RSVD = Reserved.
Full-charged is detected. FC is set when charge termination is reached and FC Set% = -1 (See the Charging and
FC = Charge Termination Indication section for details) or State of Charge is larger than FC Set% and FC Set% is not -1.
True when set.
CHG = (Fast) charging allowed. True when set.
OCVTAKEN = Cleared on entry to relax mode and set to 1 when OCV measurement is performed in relax.
ISD = Internal Short is detected. True when set.
TDD = Tab Disconnect is detected. True when set.
HW[1:0] Device Identification. Default is 01
SOC1 = State-of-Charge-Threshold 1 (SOC1 Set) reached. True when set.
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SOCF = State-of-Charge-Threshold Final (SOCF Set %) reached. True when set.
DSG = Discharging detected. True when set.
NominalAvailableCapacity( ): 0x0c/0x0d
This read-only command pair returns the uncompensated (less than C/20 load) battery capacity remaining. Units
are mAh.
FullAvailableCapacity( ): 0x0e/0x0f
This read-only command pair returns the uncompensated (less than C/20 load) capacity of the battery when fully
charged. Units are mAh. FullAvailableCapacity( ) is updated at regular intervals, as specified by the IT algorithm.
RemainingCapacity( ): 0x10/0x11
This read-only command pair returns the compensated battery capacity remaining (UnfilteredRM()) when the
[SmoothEn] bit in Operating Configuration C is cleared or filtered compensated battery capacity remaining
(FilteredRM()) when [SmoothEn] is set. Units are mAh.
FullChargeCapacity( ): 0x12/13
This read-only command pair returns the compensated capacity of fully charged battery (UnfilteredFCC()) when
the [SmoothEn] bit in Operating Configuration C is cleared or filtered compensated capacity of fully charged
battery (FilteredFCC()) when [SmoothEn] is set. Units are mAh. FullChargeCapacity() is updated at regular
intervals, as specified by the IT algorithm.
AverageCurrent( ): 0x14/0x15
This read-only command pair returns a signed integer value that is the average current flow through the sense
resistor. It is updated every 1 second. Units are mA.
TimeToEmpty( ): 0x16/0x17
This read-only function returns an unsigned integer value of the predicted remaining battery life at the present
rate of discharge, in minutes. A value of 65,535 indicates battery is not being discharged.
FilteredFCC( ): 0x18/0x19
This read-only command pair returns the filtered compensated capacity of the battery when fully charged when
the [SmoothEn] bit in Operating Configuration C is set. Units are mAh. FilteredFCC() is updated at regular
intervals, as specified by the IT algorithm.
StandbyCurrent( ): 0x1a/0x1b
This read-only function returns a signed integer value of the measured system standby current through the sense
resistor. The StandbyCurrent( ) is an adaptive measurement. Initially it reports the standby current programmed
in Initial Standby, and after spending some time in standby, reports the measured standby current.
The register value is updated every 1 second when the measured current is above the Deadband and is less
than or equal to 2 x Initial Standby. The first and last values that meet this criteria are not averaged in, since
they may not be stable values. To approximate a 1 minute time constant, each new StandbyCurrent( ) value is
computed by taking approximate 93% weight of the last standby current and approximate 7% of the current
measured average current.
UnfilteredFCC( ): 0x1c/0x1d
This read-only command pair returns the compensated capacity of the battery when fully charged. Units are
mAh. UnFilteredFCC() is updated at regular intervals, as specified by the IT algorithm.
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MaxLoadCurrent( ): 0x1e/0x1f
This read-only function returns a signed integer value, in units of mA, of the maximum load conditions of the
system. The MaxLoadCurrent( ) is an adaptive measurement which is initially reported as the maximum load
current programmed in Initial Max Load Current. If the measured current is ever greater than Initial Max Load
Current, then MaxLoadCurrent( ) updates to the new current. MaxLoadCurrent( ) is reduced to the average of
the previous value and Initial Max Load Current whenever the battery is charged to full after a previous
discharge to an SOC less than 50%. This prevents the reported value from maintaining an unusually high value.
UnfilteredRM( ): 0x20/0x21
This read-only command pair returns the compensated battery capacity remaining. Units are mAh.
FilteredRM( ): 0x22/0x23
This read-only command pair returns the filtered compensated battery capacity remaining when [SmoothEn] bit in
Operating Configuration C is set. Units are mAh.
AveragePower( ): 0x24/0x25
This read-word function returns an unsigned integer value of the average power of the current discharge. It is
negative during discharge and positive during charge. A value of 0 indicates that the battery is not being
discharged. The value is reported in units of mW (Design Energy Scale = 1) or cW (Design Energy Scale =
10).
InternalTemperature( ): 0x28/0x29
This read-only function returns an unsigned integer value of the measured internal temperature of the device in
units of 0.1K measured by the fuel gauge.
CycleCount( ): 0x2a/0x2b
This read-only function returns an unsigned integer value of the number of cycles the battery has experienced
with a range of 0 to 65,535. One cycle occurs when accumulated discharge ≥ CC Threshold.
StateOfCharge( ): 0x2c/0x2d
This read-only function returns an unsigned integer value of the predicted RemainingCapacity() expressed as a
percentage of FullChargeCapacity( ), with a range of 0 to 100%. The StateOfCharge() can be filtered or unfiltered
since RemainingCapacity() and FullChargeCapacity( ) can be filtered or unfiltered based on [SmoothEn] bit
slection.
StateOfHealth( ): 0x2e/0x2f
0x2e SOH percentage: this read-only function returns an unsigned integer value, expressed as a percentage of
the ratio of predicted FCC(25°C, SOH Load I) over the DesignCapacity(). The FCC(25°C, SOH Load I) is the
calculated full charge capacity at 25°C and the SOH current rate which is specified by SOH Load I. The range of
the returned SOH percentage is 0x00 to 0x64, indicating 0 to 100% correspondingly.
PassedCharge( ): 0x34/0x35
This signed integer indicates the amount of charge passed through the sense resistor since the last IT simulation
in mAh.
DOD0( ): 0x36/0x37
This unsigned integer indicates the depth of discharge during the most recent OCV reading.
SelfDischargeCurrent( ): 0x38/0x39
This read-only command pair returns the signed integer value that estimates the battery self discharge current.
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EXTENDED DATA COMMANDS
Extended commands offer additional functionality beyond the standard set of commands. They are used in the
same manner; however unlike standard commands, extended commands are not limited to 2-byte words. The
number of command bytes for a given extended command ranges in size from single to multiple bytes, as
specified in Table 5. For details on the SEALED and UNSEALED states, see Section Access Modes.
Table 5. Extended Commands
NAME
COMMAND CODE
Reserved
PackConfig( )
DesignCapacity( )
DataFlashClass( )
(2)
DataFlashBlock( )
(2)
BlockData( ) / Authenticate( )
(3)
BlockData( ) / AuthenticateCheckSum( )
(3)
BlockData( )
BlockDataCheckSum( )
BlockDataControl( )
DeviceNameLength( )
DeviceName( )
Reserved
(1)
(2)
(3)
UNITS
SEALED
ACCESS (1) (2)
UNSEALED
ACCESS (1) (2)
RSVD
0x38…0x39
N/A
R
R
PCR
0x3a / 0x3b
HEX#
R
R
DCAP
0x3c / 0x3d
mAh
R
R
DFCLS
0x3e
N/A
N/A
R/W
DFBLK
0x3f
N/A
R/W
R/W
A/DF
0x40…0x53
N/A
R/W
R/W
ACKS/DFD
0x54
N/A
R/W
R/W
DFD
0x55…0x5f
N/A
R
R/W
DFDCKS
0x60
N/A
R/W
R/W
DFDCNTL
0x61
N/A
N/A
R/W
DNAMELEN
0x62
N/A
R
R
DNAME
0x63...0x6c
N/A
R
R
RSVD
0x6d...0x7f
N/A
R
R
SEALED and UNSEALED states are entered via commands to Control( ) 0x00/0x01
In SEALED mode, data flash CANNOT be accessed through commands 0x3e and 0x3f.
The BlockData( ) command area shares functionality for accessing general data flash and for using Authentication. See section on
Authentication for more details.
PackConfig( ): 0x3a/0x3b
SEALED and UNSEALED Access: This command returns the value stored in Pack Configuration and is
expressed in hex value.
DesignCapacity( ): 0x3c/0x3d
SEALED and UNSEALED Access: This command returns the value stored in Design Capacity and is expressed
in mAh. This is intended to be the theoretical or nominal capacity of a new pack, but has no bearing on the
operation of the fuel gauge functionality.
DataFlashClass( ): 0x3e
This command sets the data flash class to be accessed. The subclass ID to be accessed should be entered in
hexadecimal.
SEALED Access: This command is not available in SEALED mode.
DataFlashBlock( ): 0x3f
UNSEALED Access: This command sets the data flash block to be accessed. When 0x00 is written to
BlockDataControl( ), DataFlashBlock( ) holds the block number of the data flash to be read or written. Example:
writing a 0x00 to DataFlashBlock( ) specifies access to the first 32 byte block and a 0x01 specifies access to the
second 32 byte block, and so on.
SEALED Access: This command directs which data flash block will be accessed by the BlockData( ) command.
Writing a 0x00 to DataFlashBlock( ) specifies the BlockData( ) command will transfer authentication data. Issuing
a 0x01 or 0x02 instructs the BlockData( ) command to transfer Manufacturer Info Block A or B respectively.
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BlockData( ): 0x40…0x5f
This command range is used to transfer data for data flash class access. This command range is the 32-byte
data block used to access Manufacturer Info Block A or B. Manufacturer Info Block A is read only for the
sealed access. UNSEALED access is read/write.
BlockDataChecksum( ): 0x60
The host system should write this value to inform the device that new data is ready for programming into the
specified data flash class and block.
UNSEALED Access: This byte contains the checksum on the 32 bytes of block data read or written to data flash.
The least-significant byte of the sum of the data bytes written must be complemented ( [255 – x] , for x the 8-bit
summation of the BlockData() (0x40 to 0x5F) on a byte-by-byte basis.) before being written to 0x60.
SEALED Access: This byte contains the checksum for the 32 bytes of block data written to Manufacturer Info
Block A or B. The least-significant byte of the sum of the data bytes written must be complemented ( [255 – x] ,
for x the 8-bit summation of the BlockData() (0x40 to 0x5F) on a byte-by-byte basis.) before being written to
0x60.
BlockDataControl( ): 0x61
UNSEALED Access: This command is used to control data flash access mode. The value determines the data
flash to be accessed. Writing 0x00 to this command enables BlockData( ) to access general data flash.
SEALED Access: This command is not available in SEALED mode.
DeviceNameLength( ): 0x62
UNSEALED and SEALED Access: This byte contains the length of the Device Name.
DeviceName( ): 0x63…0x6c
UNSEALED and SEALED Access: This block contains the device name that is programmed in Device Name.
Reserved – 0x6a – 0x7f
DATA FLASH INTERFACE
ACCESSING THE DATA FLASH
The bq27541-G1 data flash is a non-volatile memory that contains initialization, default, cell status, calibration,
configuration, and user information. The data flash can be accessed in several different ways, depending on
what mode the bq27541-G1 is operating in and what data is being accessed.
Commonly accessed data flash memory locations, frequently read by a system, are conveniently accessed
through specific instructions, already described in Section Data Commands. These commands are available
when the bq27541-G1 is either in UNSEALED or SEALED modes.
Most data flash locations, however, are only accessible in UNSEALED mode by use of the bq27541-G1
evaluation software or by data flash block transfers. These locations should be optimized and/or fixed during the
development and manufacture processes. They become part of a golden image file and can then be written to
multiple battery packs. Once established, the values generally remain unchanged during end-equipment
operation.
To access data flash locations individually, the block containing the desired data flash location(s) must be
transferred to the command register locations, where they can be read to the system or changed directly. This is
accomplished by sending the set-up command BlockDataControl( ) (0x61) with data 0x00. Up to 32 bytes of data
can be read directly from the BlockData( ) (0x40…0x5f), externally altered, then rewritten to the BlockData( )
command space. Alternatively, specific locations can be read, altered, and rewritten if their corresponding offsets
are used to index into the BlockData( ) command space. Finally, the data residing in the command space is
transferred to data flash, once the correct checksum for the whole block is written to BlockDataChecksum( )
(0x60).
18
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Occasionally, a data flash CLASS will be larger than the 32-byte block size. In this case, the DataFlashBlock( )
command is used to designate which 32-byte block the desired locations reside in. The correct command
address is then given by 0x40 + offset modulo 32. For example, to access Terminate Voltage in the Gas
Gauging class, DataFlashClass( ) is issued 80 (0x50) to set the class. Because the offset is 67, it must reside in
the third 32-byte block. Hence, DataFlashBlock( ) is issued 0x02 to set the block offset, and the offset used to
index into the BlockData( ) memory area is 0x40 + 67 modulo 32 = 0x40 + 16 = 0x40 + 0x03 = 0x43.
Reading and writing subclass data are block operations up to 32 bytes in length. If during a write the data length
exceeds the maximum block size, then the data is ignored.
None of the data written to memory are bounded by the bq27541-G1 — the values are not rejected by the fuel
gauge. Writing an incorrect value may result in hardware failure due to firmware program interpretation of the
invalid data. The written data is persistent, so a power-on reset does not resolve the fault.
MANUFACTURER INFORMATION BLOCKS
The bq27541-G1 contains 64 bytes of user programmable data flash storage: Manufacturer Info Block A and
Manufacturer Info Block B, . The method for accessing these memory locations is slightly different, depending
on whether the device is in UNSEALED or SEALED modes.
When in UNSEALED mode and when 0x00 has been written to BlockDataControl( ), accessing the Manufacturer
Info Blocks is identical to accessing general data flash locations. First, a DataFlashClass( ) command is used to
set the subclass, then a DataFlashBlock( ) command sets the offset for the first data flash address within the
subclass. The BlockData( ) command codes contain the referenced data flash data. When writing the data flash,
a checksum is expected to be received by BlockDataChecksum( ). Only when the checksum is received and
verified is the data actually written to data flash.
As an example, the data flash location for Manufacturer Info Block B is defined as having a Subclass = 58 and
an Offset = 32 through 63 (32 byte block). The specification of Class = System Data is not needed to address
Manufacturer Info Block B, but is used instead for grouping purposes when viewing data flash info in the
bq27541-G1 evaluation software.
When in SEALED mode or when 0x01 BlockDataControl( ) does not contain 0x00, data flash is no longer
available in the manner used in UNSEALED mode. Rather than issuing subclass information, a designated
Manufacturer Information Block is selected with the DataFlashBlock( ) command. Issuing a 0x01 or 0x02 with this
command causes the corresponding information block (A or B respectively) to be transferred to the command
space 0x40…0x5f for editing or reading by the system. Upon successful writing of checksum information to
BlockDataChecksum( ), the modified block is returned to data flash. Note: Manufacturer Info Block A is readonly when in SEALED mode.
ACCESS MODES
The bq27541-G1 provides three security modes (FULL ACCESS, UNSEALED, and SEALED) that control data
flash access permissions according to Table 6. Data Flash refers to those data flash locations, , that are
accessible to the user. Manufacture Information refers to the two 32-byte blocks.
Table 6. Data Flash Access
SECURITY MODE
DATA FLASH
MANUFACTURER INFORMATION
FULL ACCESS
R/W
R/W
UNSEALED
R/W
R/W
SEALED
None
R (A); R/W (B)
Although FULL ACCESS and UNSEALED modes appear identical, only FULL ACCESS mode allows the
bq27541-G1 to write access-mode transition keys stored in the Security class.
SEALING/UNSEALING DATA FLASH
The bq27541-G1 implements a key-access scheme to transition between SEALED, UNSEALED, and FULLACCESS modes. Each transition requires that a unique set of two keys be sent to the bq27541-G1 via the
Control( ) control command. The keys must be sent consecutively, with no other data being written to the
Control( ) register in between. Note that to avoid conflict, the keys must be different from the codes presented in
the CNTL DATA column of Table 2 subcommands.
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When in SEALED mode the [SS] bit of CONTROL_STATUS is set, but when the UNSEAL keys are correctly
received by the bq27541-G1, the [SS] bit is cleared. When the full-access keys are correctly received the
CONTROL_STATUS [FAS] bit is cleared.
Both Unseal Key and Full-Access Key have two words and are stored in data flash. The first word is Key 0 and
the second word is Key 1. The order of the keys sent to bq27541-G1 are Key 1 followed by Key 0. The order of
the bytes for each key entered through the Control( ) command is the reverse of what is read from the part. For
an example, if the Unseal Key is 0x56781234, key 1 is 0x1234 and key 0 is 0x5678. Then Control( ) should
supply 0x3412 and 0x7856 to unseal the part. The Unseal Key and the Full-Access Key can only be updated
when in FULL-ACCESS mode.
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DATA FLASH SUMMARY
Table 7 summarizes the data flash locations available to the user, including their default, minimum, and
maximum values.
Table 7. Data Flash Summary
Data
Type
Min Value
Max Value
Default Value
Units
(EVSW
Units)*
OT Chg
I2
0
1200
550
0.1°C
OT Chg Time
U1
0
60
2
s
I2
0
1200
500
0.1°C
OT Dsg
I2
0
1200
600
0.1°C
OT Dsg Time
U1
0
60
2
s
OT Dsg Recovery
I2
0
1200
550
0.1°C
0
Chg Inhibit Temp Low
I2
-400
1200
0
0.1°C
2
Chg Inhibit Temp High
I2
-400
1200
450
0.1°C
Charge Inhibit Cfg
4
Temp Hys
I2
0
100
50
0.1°C
34
Charge
0
Charging Voltage
I2
0
4600
4200
mV
Configuration
36
Charge Termination
0
Taper Current
I2
0
1000
100
mA
Configuration
36
Charge Termination
2
Min Taper Capacity
I2
0
1000
25
mAh
Configuration
36
Charge Termination
4
Taper Voltage
I2
0
1000
100
mV
Configuration
36
Charge Termination
6
Current Taper Window
U1
0
60
40
s
Configuration
36
Charge Termination
7
TCA Set %
I1
-1
100
99
%
Configuration
36
Charge Termination
8
TCA Clear %
I1
-1
100
95
%
Configuration
36
Charge Termination
9
FC Set %
I1
-1
100
-1
%
Configuration
36
Charge Termination
10
FC Clear %
I1
-1
100
98
%
Configuration
36
Charge Termination
11
DODatEOC Delta T
I2
0
1000
50
0.1°C
Configuration
48
Data
0
Rem Cap Alarm
I2
0
700
100
mA
Configuration
48
Data
8
Initial Standby
I1
-256
0
-10
mA
Configuration
48
Data
9
Initial MaxLoad
I2
-32767
0
-500
mA
Configuration
48
Data
17
Cycle Count
U2
0
65535
0
Configuration
48
Data
19
CC Threshold
I2
100
32767
900
Configuration
48
Data
23
Design Capacity
I2
0
32767
1000
mA
Configuration
48
Data
25
Design Energy
I2
0
32767
5400
mWh
Configuration
48
Data
27
SOH Load I
I2
-32767
0
-400
mA
Configuration
48
Data
29
TDD SOH Percent
I1
0
100
80
%
Configuration
48
Data
40
ISD Current
I2
0
32767
10
HourRate
Configuration
48
Data
42
ISD I Filter
U1
0
255
127
Configuration
48
Data
43
Min ISD Time
U1
0
255
7
Configuration
48
Data
44
Design Energy Scale
U1
0
255
1
Configuration
48
Data
45
Device Name
S11
x
x
bq2754X-G1
-
Configuration
49
Discharge
0
SOC1 Set Threshold
U2
0
65535
150
mAh
Configuration
49
Discharge
2
SOC1 Clear Threshold
U2
0
65535
175
mAh
Configuration
49
Discharge
4
SOCF Set Threshold
U2
0
65535
75
mAh
Configuration
49
Discharge
6
SOCF Clear Threshold
U2
0
65535
100
mAh
Configuration
49
Discharge
9
BL Set Volt Threshold
I2
0
16800
2500
mV
Configuration
49
Discharge
11
BL Set Volt Time
U1
0
60
2
s
Configuration
49
Discharge
12
BL Clear Volt Threshold
I2
0000
16800
2600
mV
Configuration
49
Discharge
14
BH Set Volt Threshold
I2
0
16800
4500
mV
Configuration
49
Discharge
16
BH Volt Time
U1
0
60
2
s
Configuration
49
Discharge
17
BH Clear Volt Threshold
I2
0000
16800
4400
mV
Configuration
56
Manufacturer Data
0
Pack Lot Code
H2
0x0
0xffff
0x0
-
Configuration
56
Manufacturer Data
2
PCB Lot Code
H2
0x0
0xffff
0x0
-
Configuration
56
Manufacturer Data
4
Firmware Version
H2
0x0
0xffff
0x0
-
Configuration
56
Manufacturer Data
6
Hardware Revision
H2
0x0
0xffff
0x0
-
Configuration
56
Manufacturer Data
8
Cell Revision
H2
0x0
0xffff
0x0
-
Configuration
56
Manufacturer Data
10
DF Config Version
H2
0x0
0xffff
0x0
-
Configuration
57
Integrity Data
6
Static Chem DF Checksum
H2
0x0
0x7fff
0x0
Class
Subclass
ID
Subclass
Offset
Configuration
2
Safety
0
Configuration
2
Safety
2
Configuration
2
Safety
3
OT Chg Recovery
Configuration
2
Safety
5
Configuration
2
Safety
7
Configuration
2
Safety
8
Configuration
32
Charge Inhibit Cfg
Configuration
32
Charge Inhibit Cfg
Configuration
32
Configuration
Name
mAh
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Table 7. Data Flash Summary (continued)
Default Value
Units
(EVSW
Units)*
1400
0
0.1°C
1400
500
0.1°C
0
32767
2800
mV
I2
0
32767
4200
mV
Lifetime Max Chg Current
I2
-32767
32767
0
mA
10
Lifetime Max Dsg Current
I2
-32767
32767
0
mA
Lifetime Temp Samples
0
LT Flash Cnt
U2
0
65535
0
64
Registers
0
Pack Configuration
H2
0x0
0xffff
0x1177
64
Registers
2
Pack Configuration B
H1
0x0
0xff
0xa7
Configuration
64
Registers
3
Pack Configuration C
H1
0x0
0xff
0x18
Configuration
66
Lifetime Resolution
0
LT Temp Res
U1
0
255
10
Num
Configuration
66
Lifetime Resolution
1
LT V Res
U1
0
255
25
Num
Configuration
66
Lifetime Resolution
2
LT Cur Res
U1
0
255
100
Num
Configuration
66
Lifetime Resolution
3
LT Update Time
U2
0
65535
60
Num
Configuration
68
Power
0
Flash Update OK Voltage
I2
0
4200
2800
mV
Configuration
68
Power
2
Sleep Current
I2
0
100
10
mA
Configuration
68
Power
11
Hibernate I
U2
0
700
8
mA
Configuration
68
Power
13
Hibernate V
U2
2400
3000
2550
mV
Configuration
68
Power
15
FS Wait
U1
0
255
0
s
System Data
58
Manufacturer Info
0-31
Block A 0-31
H1
0x0
0xff
0x0
-
System Data
58
Manufacturer Info
32-63
Block B 0-31
H1
0x0
0xff
0x0
-
Gas Gauging
80
IT Cfg
0
Load Select
U1
0
255
1
Gas Gauging
80
IT Cfg
1
Load Mode
U1
0
255
0
Gas Gauging
80
IT Cfg
21
Max Res Factor
U1
0
255
15
Gas Gauging
80
IT Cfg
22
Min Res Factor
U1
0
255
5
Gas Gauging
80
IT Cfg
25
Ra Filter
U2
0
1000
800
Gas Gauging
80
IT Cfg
42
Fast Qmax Start DOD %
U1
0
255
92
Gas Gauging
80
IT Cfg
43
Fast Qmax End DOD %
U1
0
255
96
%
Gas Gauging
80
IT Cfg
44
Fast Qmax Start Volt Delta
I2
0
4200
200
mV
Gas Gauging
80
IT Cfg
67
Terminate Voltage
I2
2800
3700
3000
mV
Gas Gauging
80
IT Cfg
69
Term V Delta
I2
0
4200
200
mV
Gas Gauging
80
IT Cfg
72
ResRelax Time
U2
0
65534
500
s
Gas Gauging
80
IT Cfg
76
User Rate-mA
I2
2000
9000
0
mA
Gas Gauging
80
IT Cfg
78
User Rate-Pwr
I2
3000
14000
0
mW/cW
Gas Gauging
80
IT Cfg
80
Reserve Cap-mAh
I2
0
9000
0
mA
Gas Gauging
80
IT Cfg
82
Reserve Energy
I2
0
14000
0
mWh/cWh
Gas Gauging
80
IT Cfg
86
Max Scale Back Grid
U1
0
15
4
Gas Gauging
80
IT Cfg
87
Max DeltaV
U2
0
65535
200
Gas Gauging
80
IT Cfg
89
Min DeltaV
U2
0
65535
0
mV
Gas Gauging
80
IT Cfg
91
Max Sim Rate
U1
0
255
1
C/rate
Gas Gauging
80
IT Cfg
92
Min Sim Rate
U1
0
255
20
C/rate
Gas Gauging
80
IT Cfg
93
Ra Max Delta
U2
0
65535
43
mΩ
Gas Gauging
80
IT Cfg
95
Qmax Max Delta %
U1
0
100
5
mAmpHour
Gas Gauging
80
IT Cfg
96
DeltaV Max Delta
U2
0
65535
10
mV
Gas Gauging
80
IT Cfg
102
Fast Scale Start SOC
U1
0
100
10
%
Gas Gauging
80
IT Cfg
103
Charge Hys V Shift
I2
0
2000
40
mV
Gas Gauging
81
Current Thresholds
0
Dsg Current Threshold
I2
0
2000
60
mA
Gas Gauging
81
Current Thresholds
2
Chg Current Threshold
I2
0
2000
75
mA
Gas Gauging
81
Current Thresholds
4
Quit Current
I2
0
1000
40
mA
Gas Gauging
81
Current Thresholds
6
Dsg Relax Time
U2
0
8191
60
s
Gas Gauging
81
Current Thresholds
8
Chg Relax Time
U1
0
255
60
s
Gas Gauging
81
Current Thresholds
9
Quit Relax Time
U1
0
63
1
s
Gas Gauging
81
Current Thresholds
10
Max IR Correct
U2
0
1000
400
mV
Gas Gauging
82
State
0
Qmax Cell 0
I2
0
32767
1000
mAh
Gas Gauging
82
State
2
Cycle Count
U2
0
65535
0
Class
Subclass
ID
Subclass
Offset
Name
Data
Type
Configuration
59
Lifetime Data
0
Lifetime Max Temp
Configuration
59
Lifetime Data
2
Lifetime Min Temp
Configuration
59
Lifetime Data
4
Configuration
59
Lifetime Data
Configuration
59
Configuration
Min Value
Max Value
I2
0
I2
-600
Lifetime Max Pack Voltage
I2
6
Lifetime Min Pack Voltage
Lifetime Data
8
59
Lifetime Data
Configuration
60
Configuration
Configuration
22
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Table 7. Data Flash Summary (continued)
Class
Subclass
ID
Subclass
Offset
Gas Gauging
82
State
Gas Gauging
82
State
Gas Gauging
82
Gas Gauging
Units
(EVSW
Units)*
Name
Data
Type
Min Value
4
Update Status
H1
0x0
0x6
0x0
5
V at Chg Term
I2
0
5000
4200
mV
State
7
Avg I Last Run
I2
-32768
32767
-299
mA
82
State
9
Avg P Last Run
I2
-32768
32767
-1131
mA
Gas Gauging
82
State
11
Delta Voltage
I2
-32768
32767
2
mV
Gas Gauging
82
State
15
T Rise
I2
0
32767
20
Num
Gas Gauging
82
State
17
T Time Constant
I2
0
32767
1000
Num
OCV Table
83
OCV Table
0
Chem ID
H2
0
FFFF
0128
num
Ra Table
88
R_a0
0
Cell0 R_a flag
H2
0x0
0x0
0xff55
-
Ra Table
88
R_a0
2-31
Cell0 R_a 0-14
I2
183
183
407
-10
Ra Table
89
R_a0x
0
xCell0 R_a flag
H2
0xffff
0xffff
0xffff
-
Ra Table
89
R_a0x
2-31
xCell0 R_a 0-14
I2
183
183
407
-10
Calibration
104
Data
0
CC Gain
F4
1.0e-1
4.0e+1
0.4768
Calibration
104
Data
4
CC Delta
F4
2.9826e+4
1.193046e+
6
567744.56
Calibration
104
Data
8
CC Offset
I2
-32768
32767
-1200
mA
Calibration
104
Data
10
Board Offset
I1
-128
127
0
uAmp
Calibration
104
Data
11
Int Temp Offset
I1
-128
127
0
Calibration
104
Data
12
Ext Temp Offset
I1
-128
127
0
Calibration
104
Data
13
Pack V Offset
I1
-128
127
0
Calibration
107
Current
1
Deadband
U1
0
255
5
mA
Security
112
Codes
0
Sealed to Unsealed
H4
0x0
0xffffffff
0x36720414
-
Security
112
Codes
4
Unsealed to Full
H4
0x0
0xffffffff
0xffffffff
-
Security
112
Codes
8
Authen Key3
H4
0x0
0xffffffff
0x01234567
-
Security
112
Codes
12
Authen Key2
H4
0x0
0xffffffff
0x89abcdef
-
Security
112
Codes
16
Authen Key1
H4
0x0
0xffffffff
0xfedcba98
-
Security
112
Codes
20
Authen Key0
H4
0x0
0xffffffff
0x76543210
-
Max Value
Default Value
2 Ω
2 Ω
Table 8. Data Flash to EVSW Conversion
Class
SubClass
ID
SubClass
Offset
Gas Gauging
80
IT Cfg
Gas Gauging
80
IT Cfg
Calibration
104
Calibration
Calibration
Calibration
EVSW
Unit
Data Flash (DF)
to EVSW
Conversion
0
mW/cW
DF × 10
0
mWh/cW
DF × 10
Num
10.124
mΩ
4.768/DF
5.595e5
Num
10.147
mΩ
5677445/DF
–1200
Num
–0.576
mV
DF × 0.00048
0
Num
0
µV
DF × 16/0.48
Name
Data
Type
Data Flash
Default
Data Flash
Unit
EVSW
Default
78
User Rate-Pwr
I2
82
Reserve Energy
I2
0
cW/10W
0
cWh/10cWh
Data
0
CC Gain
F4
0.47095
104
Data
4
104
Data
8
CC Delta
F4
CC Offset
I2
104
Data
10
Board Offset
I1
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FUNCTIONAL DESCRIPTION
FUEL GAUGING
The bq27541-G1 measures the cell voltage, temperature, and current to determine battery SOC based on
Impedance Track™ algorithm (Please refer to Application Report SLUA450 "Theory and Implementation of
Impedance Track Battery Fuel-Gauging Algorithm" for more information). The bq27541-G1 monitors charge and
discharge activity by sensing the voltage across a small-value resistor (5 mΩ to 20 mΩ typ.) between the SRP
and SRN pins and in series with the cell. By integrating charge passing through the battery, the battery’s SOC is
adjusted during battery charge or discharge.
The total battery capacity is found by comparing states of charge before and after applying the load with the
amount of charge passed. When an application load is applied, the impedance of the cell is measured by
comparing the OCV obtained from a predefined function for present SOC with the measured voltage under load.
Measurements of OCV and charge integration determine chemical state of charge and chemical capacity
(Qmax). The initial Qmax values are taken from a cell manufacturers' data sheet multiplied by the number of
parallel cells. It is also used for the value in Design Capacity. The bq27541-G1 acquires and updates the
battery-impedance profile during normal battery usage. It uses this profile, along with SOC and the Qmax value,
to determine FullChargeCapacity( ) and StateOfCharge( ), specifically for the present load and temperature.
FullChargeCapacity( ) is reported as capacity available from a fully charged battery under the present load and
temperature until Voltage( ) reaches the Terminate Voltage. NominalAvailableCapacity( ) and
FullAvailableCapacity( ) are the uncompensated (no or light load) versions of RemainingCapacity( ) and
FullChargeCapacity( ) respectively.
The bq27541-G1 has two flags accessed by the Flags( ) function that warns when the battery’s SOC has fallen
to critical levels. When RemainingCapacity( ) falls below the first capacity threshold, specified in SOC1 Set
Threshold, the [SOC1] (State of Charge Initial) flag is set. The flag is cleared once RemainingCapacity( ) rises
above SOC1 Clear Threshold. All units are in mAh.
When RemainingCapacity( ) falls below the second capacity threshold, SOCF Set Threshold, the [SOCF] (State
of Charge Final) flag is set, serving as a final discharge warning. If SOCF Set Threshold = –1, the flag is
inoperative during discharge. Similarly, when RemainingCapacity( ) rises above SOCF Clear Threshold and the
[SOCF] flag has already been set, the [SOCF] flag is cleared. All units are in mAh.
The bq27541-G1 has two additional flags accessed by the Flags() function that warns of internal battery
conditions. The fuel gauge monitors the cell voltage during relaxed conditions to determine if an internal short
has been detected. When this condiitons occurs, [ISD] will be set. The bq27541-G1 also has the capability of
detecting when a tab has been disconnected in a 2-cell parallel system by actively monitoring the SOH. When
this conditions occurs, [TDD] will be set.
IMPEDANCE TRACK™ VARIABLES
The bq27541-G1 has several data flash variables that permit the user to customize the Impedance Track™
algorithm for optimized performance. These variables are dependent upon the power characteristics of the
application as well as the cell itself.
Load Mode
Load Mode is used to select either the constant-current or constant-power model for the Impedance Track™
algorithm as used in Load Select (see Load Select). When Load Mode is 0, the Constant Current Model is
used (default). When Load Mode is 1, the Constant Power Model is used. The [LDMD] bit of
CONTROL_STATUS reflects the status of Load Mode.
Load Select
Load Select defines the type of power or current model to be used to compute load-compensated capacity in the
Impedance Track™ algorithm. If Load Mode = 0 (Constant Current), then the options presented in Table 9 are
available.
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Table 9. Constant-Current Model Used when Load Mode = 0
LoadSelect Value
0
CURRENT MODEL USED
Average discharge current from previous cycle: There is an internal register that records the average discharge current through each
entire discharge cycle. The previous average is stored in this register.
1(default)
Present average discharge current: This is the average discharge current from the beginning of this discharge cycle until present time.
2
Average current: based off the AverageCurrent( )
3
Current: based off of a low-pass-filtered version of AverageCurrent( ) (τ = 14s)
4
Design capacity / 5: C Rate based off of Design Capacity /5 or a C / 5 rate in mA.
5
Use the value specified by AtRate( )
6
Use the value in User_Rate-mA: This gives a completely user-configurable method.
If Load Mode = 1 (Constant Power) then the following options are available:
Table 10. Constant-Power Model Used When Load Mode = 1
LoadSelect Value
POWER MODEL USED
0
Average discharge power from previous cycle: There is an internal register that records the average discharge power through each
entire discharge cycle. The previous average is stored in this register.
1
Present average discharge power: This is the average discharge power from the beginning of this discharge cycle until present time.
2
Average current × voltage: based off the AverageCurrent( ) and Voltage( ).
3
Current × voltage: based off of a low-pass-filtered version of AverageCurrent( ) (τ = 14s) and Voltage( )
4
Design energy / 5: C Rate based off of Design Energy /5 or a C / 5 rate in mA .
5
Use the value specified by AtRate( )
6
Use the value in User_Rate-Pwr. This gives a completely user- configurable method.
Reserve Cap-mAh
Reserve Cap-mAh determines how much actual remaining capacity exists after reaching 0
RemainingCapacity( ), before Terminate Voltage is reached when Load Mode = 0 is selected. A loaded rate
or no-load rate of compensation can be selected for Reserve Cap by setting [RESCAP] bit in Pack Configuration
Register.
Reserve Energy
Reserve Energy determines how much actual remaining capacity exists after reaching 0 RemainingCapacity( )
which is equivalent to 0 remaining power , before Terminate Voltage is reached when Load Mode = 1 is
selected. A loaded rate or no-load rate of compensation can be selected for Reserve Cap by setting [RESCAP]
bit in Pack Configuration Register.
Design Energy Scale
Design Energy Scale is used to select the scale/unit of a set of data flash parameters. The value of Design
Energy Scale can be either 1 or 10 only, other values are not supported. For battery capacities larger than 6AHr,
Design Energy Scale = 10 is recommended.
Table 11. Data Flash Parameter scale/unit based on Design Energy Scale
DATA FLASH
DESIGN ENERGY SCALE = 1 (default)
DESIGN ENERGY SCALE = 10
Design Energy
mWh
cWh
Reserve Energy
mWh
cWh
Avg Power Last Run
mW
cW
User Rate-Pwr
mWh
cWh
T Rise
No Scale
Scaled by x10
Dsg Current Threshold
This register is used as a threshold by many functions in the bq27541-G1 to determine if actual discharge current
is flowing into or out of the cell. The default for this register should be sufficient for most applications. This
threshold should be set low enough to be below any normal application load current but high enough to prevent
noise or drift from affecting the measurement.
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Chg Current Threshold
This register is used as a threshold by many functions in the bq27541-G1 to determine if actual charge current is
flowing into or out of the cell. The default for this register should be sufficient for most applications. This threshold
should be set low enough to be below any normal charge current but high enough to prevent noise or drift from
affecting the measurement.
Quit Current, Dsg Relax Time, Chg Relax Time, and Quit Relax Time
The Quit Current is used as part of the Impedance Track™ algorithm to determine when the bq27541-G1 enters
relaxation mode from a current flowing mode in either the charge direction or the discharge direction. The value
of Quit Current is set to a default value that should be above the standby current of the system.
Either of the following criteria must be met to enter relaxation mode:
1. | AverageCurrent( ) | < | Quit Current | for Dsg Relax Time.
2. | AverageCurrent( ) | < | Quit Current | for Chg Relax Time.
After about 6 minutes in relaxation mode, the bq27541-G1 attempts to take accurate OCV readings. An
additional requirement of dV/dt < 1 µV/sec is required for the bq27541-G1 to perform Qmax updates. These
updates are used in the Impedance Track™ algorithms. It is critical that the battery voltage be relaxed during
OCV readings and that the current is not higher than C/20 when attempting to go into relaxation mode.
Quit Relax Time specifies the minimum time required for AverageCurrent( ) to remain above the QuitCurrent
threshold before exiting relaxation mode.
Qmax
Qmax contains the maximum chemical capacity of the active cell profiles, and is determined by comparing states
of charge before and after applying the load with the amount of charge passed. They also correspond to capacity
at low rate of discharge, such as C/20 rate. For high accuracy, this value is periodically updated by the bq27541G1 during operation. Based on the battery cell capacity information, the initial value of chemical capacity should
be entered in Qmax field. The Impedance Track™ algorithm will update this value and maintain it in the Pack
profile.
Update Status
The Update Status register indicates the status of the Impedance Track algorithm.
Table 12. Update Status Definitions
UPDATE STATUS
STATUS
0x02
Qmax and Ra data are learned, but Impedance Track™ is not enabled. This should be the standard setting for a
golden image.
0x04
Impedance Track™ is enabled but Qmax and Ra data are not learned.
0x05
Impedance Track™ is enabled and only Qmax has been updated during a learning cycle.
0x06
Impedance Track™ is enabled. Qmax and Ra data are learned after a successful learning cycle. This should be the
operation setting for end equipment.
This register should only be updated by the bq27541-G1 during a learning cycle or when IT_ENABLE()
subcommand is received. Refer to the application note How to Generate Golden Image for Single-Cell
Impedance Track™Device (SLUA544) for learning cycle details.
Avg I Last Run
The bq27541-G1 logs the current averaged from the beginning to the end of each discharge cycle. It stores this
average current from the previous discharge cycle in this register. This register should never need to be
modified. It is only updated by the bq27541-G1 when required.
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Avg P Last Run
The bq27541-G1 logs the power averaged from the beginning to the end of each discharge cycle. It stores this
average power from the previous discharge cycle in this register. To get a correct average power reading the
bq27541-G1 continuously multiplies instantaneous current times Voltage( ) to get power. It then logs this data to
derive the average power. This register should never need to be modified. It is only updated by the bq27541-G1
when required.
Delta Voltage
The bq27541-G1 stores the maximum difference of Voltage( ) during short load spikes and normal load, so the
Impedance Track™ algorithm can calculate remaining capacity for pulsed loads. It is not recommended to
change this value.
Ra Tables and Ra Filtering Related Parameters
These tables contain encoded data and are automatically updated during device operation. The bq27541-G1 has
a filtering process to eliminate unexpected fluctuations in Ra values while the Ra values are being updated. The
DF parameters RaFilter, RaMaxDelta, MaxResfactor and MinResfactor control the Filtering process of Ra
values. RaMaxDelta Limits the change in Ra values to an absolute magnitude. MinResFactor and
MaxResFactor parameters are cumulative filters which limit the change in Ra values to a scale on a per
discharge cycle basis. These values are Data Flash configurable. No further user changes should be made to Ra
values except for reading/writing the values from a prelearned pack (part of the process for creating golden
image files).
MaxScaleBackGrid
MaxScaleBackGrid parameter limits the resistance grid point after which back scaling will not be performed. This
variable ensures that the resistance values in the lower resistance grid points remain accurate while the battery
is at a higher DoD state.
Max DeltaV, Min DeltaV
Maximal / Minimal value allowed for delta V, which will be subtracted from simulated voltage during remaining
capacity simulation.
Qmax Max Delta %
Maximal change of Qmax during one update, as percentage of Design Capacity. If the gauges attempts to
change Qmax exceeds this limit, changed value will be capped to old value ± DesignCapacity*QmaxMaxDelta /
100.
Fast Resistance Scaling
When Fast Resistance Scaling is enabled by setting the [FConvEn] bit in Pack Configuration B, the algorithm
improves accuracy at the end of discharge. The RemainingCapacity() and StateOfCharge() should smoothly
converge to 0. The algorithm starts convergence improvements when cell voltage goes below (Terminate
Voltage + Term V Delta) or StateofCharge() goes below Fast Scale Start SOC. For most applications, the
default value of Term V Delta and Fast Scale Start SOC are recommended. Also it is recommended to keep
(Terminate Voltage + Term V Delta) below 3.6V for most battery applications.
Fast Qmax Update
This new algorithm improvement provides a fast Qmax update feature that can compute Qmax based on Full
charge and end of discharge conditions without battery relaxation. The feature can be enabled by setting the
[FASTQMAX] bit in Pack Configuration C. Several data flash parameters (Fast Qmax Start DOD%, Fast
Qmax End DOD%, and Fast Qmax Start Voltage Delta) are used to configure the algorithm and default
settings are recommended. Please note that Fast Qmax Update algorithm is not used during learning cycle.
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StateOfCharge() Smoothing
When operating conditions change (such as temperature, discharge current, and resistance etc.), it can lead to
large changes of compensated battery capacity and battery capacity remaining. These changes can result in
large changes of StateOfCharge(). When [SmoothEn] is enabled in Operating Configuration C, the smoothing
algorithm injects gradual changes of battery capacity when conditions vary. This results in a gradual change of
StateOfCharge() and can provide a better end-user experience for StateOfCharge() reporting.
The RemainingCapacity(), FullChargeCapacity(), and StateOfCharge() are modified depending on [SmoothEn] as
below.
[SmoothEn]
RemainingCapacity()
FullChargeCapacity()
StateOfCharge()
0
UnfilteredRM()
UnfilteredFCC()
UnfilteredRM()/UnfilteredFCC()
1
FilteredRM()
FilteredFCC()
FilteredRM()/FilteredFCC()
DeltaV Max Delta
Maximal change of Delta V value. If attempted change of the value exceeds this limit, change value will be
capped to old value ±DeltaV Max Delta.
Lifetime Data Logging Parameters
The Lifetime Data logging function helps development and diagnosis with the bq27541-G1. Note that
IT_ENABLE needs to be enabled (Command 0x0021) for lifetime data logging functions to be active. bq27541G1 logs the lifetime data as specified in the Lifetime Data and Lifetime Temp Samples data Flash Subclasses.
The data log recordings are controlled by the Lifetime Resolution data flash Subclass.
The Lifetime Data Logging can be started by setting the IT_ENABLE bit and setting the Update Time register to a
non-zero value.
Once the Lifetime Data Logging function is enabled, the measured values are compared to what is already
stored in the Data Flash. If the measured value is higher than the maximum or lower than the minimum value
stored in the Data Flash by more than the "Resolution" set for at least one parameter, the entire Data Flash
Lifetime Registers are updated after at least LTUpdateTime.
LTUpdateTime sets the minimum update time between DF writes. When a new max/min is detected, a LT
Update window of [update time] second is enabled and the DF writes occur at the end of this window. Any
additional max/min value detected within this window will also be updated. The first new max/min value detected
after this window will trigger the next LT Update window.
Internal to bq27541-G1, there exists a RAM max/min table in addition to the DF max/min table. The RAM table is
updated independent of the resolution parameters. The DF table is updated only if at least one of the RAM
parameters exceeds the DF value by more than resolution associated with it. When DF is updated, the entire
RAM table is written to DF. Consequently, it is possible to see a new max/min value for a certain parameter even
if the value of this parameter never exceeds the maximum or minimum value stored in the Data Flash for this
parameter value by the resolution amount.
The Life Time Data Logging of one or more parameters can be reset or restarted by writing new default (or
starting) values to the corresponding Data Flash registers through sealed or unsealed access as described
below. However, when using unsealed access, new values will only take effect after device reset
The logged data can be accessed as R/W in unsealed mode from Lifetime Data SubClass (SubClass ID=59) of
Data Flash. Lifetime data may be accessed (R/W) when sealed using a process identical Manufacturer Info Block
B. The DataFlashBlock command code is 4. Note only the first 32 bytes of lifetime data (not resolution
parameters) can be R/W when sealed. See Manufacturers Info Block section for sealed access. The logging
settings such as Temperature Resolution, Voltage Resolution, Current Resolution, and Update Time can be
configured only in unsealed mode by writing to the Lifetime Resolution Subclass (SubClassID=66) of the Data
Flash.
The Lifetime resolution registers contain the parameters which set the limits related to how much a data
parameter must exceed the previously logged Max/Min value to be updated in the lifetime log. For example, V
must exceed MaxV by more than Voltage Resolution to update MaxV in the Data Flash.
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DETAILED CONFIGURATION REGISTERS DESCRIPTIONS
The Pack Configuration Register
Some bq27541-G1 pins are configured via the Pack Configuration data flash register, as indicated in Table 13.
This register is programmed/read via the methods described in Accessing the Data Flash. The register is located
at subclass = 64, offset = 0.
Table 13. Pack Configuration Bit Definition
bit7
bit6
bit5
bit4
bit3
bit2
bit1
bit0
High Byte
RESCAP
CALEN
INTPOL
INTSEL
RSVD
IWAKE
RSNS1
RSNS0
Low Byte
GNDSEL
RFACTSTEP
SLEEP
RMFCC
SE_PU
SE_POL
SE_EN
TEMPS
RESCAP = No-load rate of compensation is applied to the reserve capacity calculation. True when set. Default is 0.
CALEN bq27541-G1 Calibration mode is enabled. Default is 0.
INTPOL = Polarity for Interrupt pin. Default is 0.
INTSEL = Interrupt Pin select: 0 = SE Pin, 1 = HDQ pin. Default is 1.
RSVD = Reserved. Must be 0.
IWAKE/RSNS1/RSNS0 = These bits configure the current wake function (see Table 21). Default is 0/0/1.
GNDSEL = The ADC ground select control. The VSS (Pin 6) is selected as ground reference when the bit is clear. Pin 7 is
selected when the bit is set. Default is 0.
RFACTSTEP = Enables Ra step up/down to Max/Min Res Factor before disabling Ra updates. Default is 1
SLEEP = The fuel gauge can enter sleep, if operating conditions allow. True when set. Default is 1.
RMFCC = RM is updated with the value from FCC, on valid charge termination. True when set. Default is 1.
SE_PU = Pull-up enable for SE pin. True when set (push-pull). Default is 0.
SE_POL = Polarity bit for SE pin. SE is active low when clear (makes SE low when gauge is ready for shutdown).
Default is 1 (makes SE high when gauge is ready for shutdown).
SE_EN = Indicates if set the shutdown feature is enabled. True when set. See the System Shutdown Enable section for
details. Default is 1.
TEMPS = Selects external thermistor for Temperature( ) measurements. True when set. Default is 1.
Pack Configuration B Register
Some bq27541-G1 pins are configured via the Pack Configuration B data flash register, as indicated in
Table 14. This register is programmed/read via the methods described in Accessing the Data Flash. The register
is located at subclass = 64, offset = 2.
Table 14. Pack Configuration B Bit Definition
bit7
bit6
bit5
bit4
bit3
bit2
bit1
bit0
ChgDoDEoC
SE_TDD
VconsEN
SE_ISD
RSVD
LFPRelax
DoDWT
FConvEn
ChgDoDEoC =
Enable DoD at EoC recalculation during charging only. True when set. Default is 1. Default setting is
recommended.
SE_TDD = Enable Tab Disconnection Detection. True when set. Default is 0.
VconsEN = Enable voltage consistency check. True when set. Default is 1. Default setting is recommended.
SE_ISD = Enable Internal Short Detection. True when set. Default is 0.
RSVD = Reserved. Must be 0
LFPRelax = Enable LiFePO4 long relaxation mode when chemical ID 400 series is selected. True when set. Default is 1.
DoDWT = Enable Dod weighting for LiFePO4 support when chemical ID 400 series is selected. True when set. Default is
1.
FConvEn = Enable fast convergence algorithm. Default is 1. Default setting is recommended.
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Pack Configuration C Register
Some bq27541-G1 algorithm settings are configured via the Pack Configuration C data flash register, as
indicated in . This register is programmed/read via the methods described in Accessing the Data Flash. The
register is located at subclass = 64, offset = 3.
Table 15. Pack Configuration C Bit Definition
bit7
bit6
bit5
bit4
bit3
bit2
bit1
bit0
FastQmax
RSVDSBS
RelaxRCJumpOK
SmoothEn
SleepWkChg
RSVD
RSVD
RSVD
FastQmax = Enable Fast Qmax Update mode. True when set. Default is 0. Default setting is recommended.
RSVDSBS = Reserved. Must be 0.
RSVD = Reserved. Must be 0.
RelaxRCJumpOK =
Allow SOC to change due to temperature change during relaxation when SOC smoothing algorithm is enabled.
True when set. Default is 0
SmoothEn = Enable SOC smoothing algorithm. True when set. Default is 1
SleepWkChg = Enables compensation for the passed charge missed when waking from SLEEP mode. Default is 1
SYSTEM CONTROL FUNCTION
The bq27541-G1 provides system control functions which allows the fuel gauge to enter shutdown mode in order
to power-off with the assistance of external circuit or provides interrupt function to the system. Table 16 shows
the configurations for SE and HDQ pins.
Table 16. SE and HDQ Pin Function
COMMUNICATION
MODE
[INTSEL]
I2C
0 (default)
HDQ
I2C
1
(1)
(2)
HDQ
SE PIN FUNCTION
Interrupt Mode
HDQ PIN FUNCTION
Not Used
(1)
HDQ Mode (2)
Interrupt Mode
Shutdown Mode
HDQ Mode (2)
[SE_EN] bit in Pack Configuration can be enabled to use [SE] and [SHUTDWN] bits in
CONTROL_STATUS() function; The SE pin shutdown function is disabled.
HDQ pin is used for communication and HDQ Host Interrupt Feature is available.
Shutdown Mode
In the shutdown mode, the SE pin is used to signal external circuit to power-off the fuel gauge. This feature is
useful to shutdown the fuel gauge in a deeply discharged battery to protect the battery. By default, the Shutdown
Mode is in normal state. By sending the SET_SHUTDOWN subcommand or setting the [SE_EN] bit in Pack
Configuration register, the [SHUTDWN] bit is set and enables the shutdown feature. When this feature is
enabled and [INTSEL] is set, the SE pin can be in normal state or shutdown state. The shutdown state can be
entered in HIBERNATE mode (ONLY if HIBERNATE mode is enabled due to low cell voltage), all other power
modes will default SE pin to normal state. Table 17 shows the SE pin state in normal or shutdown mode. The
CLEAR_SHUTDOWN subcommand or clearing [SE_EN] bit in the Pack Configuration register can be used to
disable shutdown mode.
The bq27541-G1 SE pin will be high impedance at power on reset (POR), the [SE_POL] does not affect the state
of SE pin at POR. Also [SE_PU] configuration changes will only take effect after POR. In addition, the [INTSEL]
only controls the behavior of the SE pin; it does not affect the function of [SE] and [SHUTDWN] bits.
Table 17. SE Pin State
Shutdown Mode
[INTSEL] = 1 and
([SE_EN] or [SHUTDOWN] =1)
30
[SE_PU]
[SE_POL]
Normal state
Shutdown state
0
0
High Impedance
0
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Table 17. SE Pin State (continued)
0
1
0
High Impedance
1
0
1
0
1
1
0
1
Interrupt Mode
By utilizing the interrupt mode, the system can be interrupted based on detected fault conditions as specified in
Table 20. The SE or HDQ pin can be selected as the interrupt pin by configuring the [INTSel] bit based on . In
addition, the pin polarity and pull-up (SE pin only) can be configured according to the system needs as described
in Table 18 or Table 19.
Table 18. SE Pin in Interrupt Mode ([INTSEL]=0)
[SE_PU]
[INTPOL]
INTERRUPT CLEAR
INTERRUPT SET
0
0
High Impedance
0
0
1
0
High Impedance
1
0
1
0
1
1
0
1
Table 19. HDQ Pin in Interrupt Mode ([INTSEL]=1)
[INTPOL]
INTERRUPT CLEAR
0
High Impedance
INTERRUPT SET
0
1
0
High Impedance
Table 20. Interrupt Mode Fault Conditions
INTERRUPT CONDITION
Flags() STATUS
BIT
ENABLE CONDITION
SOC1 Set/Clear
[SOC1]
Always
The SOC1 Set/Clear interrupt is based on the[SOC1] Flag
condition when RemainingCapacity() reaches the SOC1 Set
or Clear threshold in the Data Flash.
Over Temperature Charge
[OTC]
OT Chg Time ≠ 0
The [OTC] Flag is set/clear based on conditions specified in
“Over-Temperature: Charge” Section.
Over Temperature
Discharge
[OTD]
OT Dsg Time ≠ 0
The [OTD] Flag is set/clear based on conditions specified in
“Over-Temperature: Discharge” Section.
Battery High
[BATHI]
Always
The [BATHI] Flag is set/clear based on conditions specified in
“BATTERY LEVEL INDICATION” Section.
Battery Low
[BATLOW]
Always
The [BATLOW] Flag is set/clear based on conditions
specified in “BATTERY LEVEL INDICATION” Section.
Internal Short Detection
[ISD]
[SE_ISD]=1 in
Pack Configuration B
The [SE_ISD] Flag is set/clear based on conditions specified
in “INTERNAL SHORT DETECTION” Section
Tab disconnection
detection
[TDD]
[SE_TDD]=1 in
Pack Configuration B
The [TDD] Flag is set/clear based on conditions specified in
“TAB DISCONNECTION DETECTION” Section
COMMENT
Battery Level Indication
The bq27541-G1 can indicate when battery voltage has fallen below or risen above predefined thresholds. The
[BATHI] of Flags() is set high to indicate Voltage() is above the BH Set Volt Threshold for a predefined duration
set in the BH Volt Time. This flag returns to low once battery voltage is below or equal the BH Clear Volt
threshold. It is recommended that the BH Set Volt Threshold is configured higher than the BH Clear Volt
threshold to provide proper voltage hysteresis.
The [BATLOW] of Flags() is set high to indicate Voltage() is below the BL Set Volt Threshold for predefined
duration set in the BL Volt Time. This flag returns to low once battery voltage is above or equal the BL Clear
Volt threshold. It is recommended that the BL Set Volt Threshold is configured lower than the BL Clear Volt
threshold to provide proper voltage hysteresis.
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The [BATHI] and [BATLOW] flags can be configured to control the interrupt pin (SE or HDQ) by enabling
interrupt mode. Refer to “Interrupt Mode” section for details.
Internal Short Detection
The bq27541-G1 can indicate detection of an internal battery short by setting the [SE_ISD] bit in Pack
Configuraton B. The device compares the self-discharge current calculated based StateOfCharge() in relaxation
mode and AverageCurrent() measured in the system. The self-discharge rate is measured at 1 hour interval.
When battery SelfDischargeCurrent() is less than the predefined (-Design Capacity / ISD Current threshold),
the [ISD] of Flags() is set high. The [ISD] of Flags() can be configured to control interrupt pin (SE or HDQ) by
enabling interrupt mode. Refer to “Interrupt Mode” section for details.
Tab Disconnection Detection
The bq27541-G1 can indicate tab disconnection by detecting change of StateOfHealth(). This feature is enabled
by setting [SE_TDD] bit in Pack Configuraton B. The [TDD] of Flags() is set when the ratio of current
StateOfHealth() divided by the previous StateOfHealth() reported is less than TDD SOH Percent. The [TDD] of
Flags() can be configured to control an interrupt pin (SE or HDQ) by enabling interrupt mode. Refer to “Interrupt
Mode” section for details.
TEMPERATURE MEASUREMENT AND THE TS INPUT
The bq27541-G1 measures battery temperature via the TS input in order to supply battery temperature status
information to the fuel gauging algorithm and charger-control sections of the gauge. Alternatively, the gauge can
also measure internal temperature via its on-chip temperature sensor, but only if the [TEMPS] bit of Pack
Configuration register is cleared.
Regardless of which sensor is used for measurement, a system processor can request the current battery
temperature by calling the Temperature( ) function (see Section Standard Data Commands, for specific
information).
The thermistor circuit requires the use of an external 10kΩ thermistor with negative temperature coefficient (NTC)
thermistor with R25 = 10kΩ ± 1% and B25/85 = 3435kΩ ± 1% (such as Semitec 103AT) that connects between
the Vcc and TS pins. Additional circuit information for connecting the thermistor to the bq27541 is shown in the
Reference Schematic.
OVER-TEMPERATURE INDICATION
Over-Temperature: Charge
If during charging, Temperature( ) reaches the threshold of OT Chg for a period of OT Chg Time and
AverageCurrent( ) ≥ Chg Current Threshold, then the [OTC] bit of Flags( ) is set. When Temperature( ) falls to
OT Chg Recovery, the [OTC] of Flags( ) is reset.
If OT Chg Time = 0, the feature is disabled.
Over-Temperature: Discharge
If during discharging, Temperature( ) reaches the threshold of OT Dsg for a period of OT Dsg Time, and
AverageCurrent( ) ≤ -Dsg Current Threshold, then the [OTD] bit of Flags( ) is set. When Temperature( ) falls to
OT Dsg Recovery, the [OTD] bit of Flags( ) is reset.
If OT Dsg Time = 0, the feature is disabled.
CHARGING AND CHARGE TERMINATION INDICATION
Detection Charge Termination
For proper bq27541-G1 operation, the cell charging voltage must be specified by the user. The default value for
this variable is in the data flash Charging Voltage.
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The bq27541-G1 detects charge termination when (1) during 2 consecutive periods of Current Taper Window,
the AverageCurrent( ) is < Taper Current, (2) during the same periods, the accumulated change in capacity >
0.25mAh / Current Taper Window, and (3) Voltage( ) > Charging Voltage – Taper Voltage. When this occurs,
the [CHG] bit of Flags( ) is cleared. Also, if the [RMFCC] bit of Pack Configuration is set, RemainingCapacity( )
is set equal to FullChargeCapacity( ). When TCA_Set is set to -1, it disables the use of the charger alarm
threshold. In that case, TerminateCharge is set when the taper condition is detected. When FC_Set is set to -1, it
disables the use of the full charge detection threshold. In that case, the [FC] bit is not set until the taper condition
is met.
Charge Inhibit
The bq27541-G1 can indicate when battery temperature has fallen below or risen above predefined thresholds
(Charge Inhibit Temp Low and Charge Inhibit Temp High, respectively). In this mode, the [CHG_INH] of
Flags( ) is made high to indicate this condition, and is returned to its low state, once battery temperature returns
to the range [Charge Inhibit Temp Low + Temp Hys, Charge Inhibit Temp High – Temp Hys].
POWER MODES
The bq27541-G1 has three power modes: NORMAL, SLEEP, and HIBERNATE. In NORMAL mode, the
bq27541-G1 is fully powered and can execute any allowable task. In SLEEP mode the fuel gauge exists in a
reduced-power state, periodically taking measurements and performing calculations. Finally, in HIBERNATE
mode, the fuel gauge is in a very low power state, but can be awoken by communication or certain I/O activity.
The relationship between these modes is shown in . Details are described in the sections that follow.
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POR
Exit From HIBERNATE
VCELL < POR threshold
Exit From HIBERNATE
Communication Activity
NORMAL
OR
bq27541 clears Control Status
[HIBERNATE] = 0
Recommend Host also set Control
Status [HIBERNATE] = 0
Fuel gauging and data
updated every 1s
Exit From SLEEP
Pack Configuration [SLEEP] = 0
OR
| AverageCurrent( ) | > Sleep Current
OR
Current is Detected above IWAKE
Entry to SLEEP
Pack Configuration [SLEEP] = 1
AND
| AverageCurrent( ) |≤ Sleep Current
SLEEP
Fuel gauging and data
updated every 20 seconds
HIBERNATE
Wakeup From HIBERNATE
Communication Activity
AND
Comm address is NOT for bq27541
Disable all bq27541
subcircuits except GPIO.
Entry to WAITFULLSLEEP
Host must set Control Status
[FULLSLEEP]=1 and
Full Sleep Wait Time > 0
Exit From WAIT_HIBERNATE
Cell not relaxed
OR
| AverageCurrent() | =>Hibernate Current
Exit From WAIT_HIBERNATE
VCELL < Hibernate Voltage
(Supports SE pin shutdown function)
Exit From WAITFULLSLEEP
Any Communication Cmd
WAITFULLSLEEP
FULLSLEEP Count Down
Entry to FULLSLEEP
Count <1
WAIT_HIBERNATE
Exit From FULLSLEEP
Any Communication Cmd
Note: Control Status [FULLSLEEP]
is cleared if Full Sleep Wait Time
<= 0
FULLSLEEP
OR
Host has set Control Status
[HIBERNATE] = 1
Fuel gauging and data
updated every 20 seconds
Exit From SLEEP
Cell relaxed
AND
| AverageCurrent() | < Hibernate Current
In low power state of SLEEP
mode. Gas gauging and data
updated every 20 seconds
NOTE: FULLSLEEP mode is disabled
when FULLSLEEP Wait Time = 0
System Shutdown
System Sleep
Figure 3. Power Mode Diagram
NORMAL MODE
The fuel gauge is in NORMAL Mode when not in any other power mode. During this mode, AverageCurrent( ),
Voltage( ) and Temperature( ) measurements are taken, and the interface data set is updated. Decisions to
change states are also made. This mode is exited by activating a different power mode.
Because the gauge consumes the most power in NORMAL mode, the Impedance Track™ algorithm minimizes
the time the fuel gauge remains in this mode.
SLEEP MODE
SLEEP mode is entered automatically if the feature is enabled (Pack Configuration [SLEEP]) = 1) and
AverageCurrent( ) is below the programmable level Sleep Current. Once entry into SLEEP mode has been
qualified, but prior to entering it, the bq27541-G1 performs an ADC autocalibration to minimize offset.
While in SLEEP mode, the fuel gauge can suspend serial communications as much as 4ms by holding the comm
line(s) low. This delay is necessary to correctly process host communication, since the fuel gauge processor is
mostly halted in SLEEP mode.
During the SLEEP mode, the bq27541-G1 periodically takes data measurements and updates its data set.
However, a majority of its time is spent in an idle condition.
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The bq27541-G1 exits SLEEP if any entry condition is broken, specifically when (1) AverageCurrent( ) rises
above Sleep Current, or (2) a current in excess of IWAKE through RSENSE is detected when the Iwake comparator
is enabled.
FULLSLEEP MODE
FULLSLEEP mode is enabled by setting the [FULLSLEEP] bit in the Control Status register. FULLSLEEP mode
is entered automatically when the bq27541-G1 is in SLEEP mode and the timer counts down to 0 (Full Sleep
Wait Time > 0). FULLSLEEP mode is entered immediately when Full Sleep Wait Time is set to 0.
During FULLSLEEP mode, the bq27541-G1 periodically takes data measurements and updates its data set.
However, a majority of its time is spent in an idle condition.
The gauge exits the FULLSLEEP mode when there is any communication activity. The [FULLSLEEP] bit can
remain set (Full Sleep Wait Time > 0) or be cleared (Full Sleep Wait Time ≤ 0) after exit of FULLSLEEP mode.
Therefore, EVSW communication activity might cause the gauge to exist FULLSLEEP MODE and display the
[FULLSLEEP] bit as clear. The execution of SET_FULLSLEEP to set [FULLSLEEP] bit is required when Full
Sleep Wait Time ≤ 0 in order to re-enter FULLSLEEP mode. The FULLSLEEP mode can be verified by
measuring the current consumption of the gauge. In this mode, the high frequency oscillator is turned off. The
power consumption is further reduced in this mode compared to the SLEEP mode.
While in FULLSLEEP mode, the fuel gauge can suspend serial communications as much as 4ms by holding the
comm line(s) low. This delay is necessary to correctly process host communication, since the fuel gauge
processor is mostly halted in SLEEP mode.
The bq27541-G1 exits SLEEP if any entry condition is broken, specifically when (1) AverageCurrent( ) rises
above Sleep Current, or (2) a current in excess of IWAKE through RSENSE is detected when the Iwake comparator
is enabled.
HIBERNATE MODE
HIBERNATE mode should be used for long-term pack storage or when the host system needs to enter a lowpower state, and minimal gauge power consumption is required. This mode is ideal when the host is set to its
own HIBERNATE, SHUTDOWN, or OFF modes. The gauge waits to enter HIBERNATE mode until it has taken a
valid OCV measurement (cell relaxed) and the magnitude of the average cell current has fallen below Hibernate
Current. When the conditions are met, the fuel gauge can enter HIBERNATE due to either low cell voltage or by
having the [HIBERNATE] bit of the CONTROL_STATUS register set. The gauge will remain in HIBERNATE
mode until any communication activity appears on the communication lines and the address is for bq27541. In
addition, the SE pin shutdown mode function is supported only when the fuel gauge enters HIBERNATE due to
low cell voltage.
When the gauge wakes up from HIBERNATE mode, the [HIBERNATE] bit of the CONTROL_STATUS register is
cleared. The host is required to set the bit in order to allow the gauge to re-enter HIBERNATE mode if desired.
Because the fuel gauge is dormant in HIBERNATE mode, the battery should not be charged or discharged in this
mode, because any changes in battery charge status will not be measured. If necessary, the host equipment can
draw a small current (generally infrequent and less than 1mA, for purposes of low-level monitoring and updating);
however, the corresponding charge drawn from the battery will not be logged by the gauge. Once the gauge
exits to NORMAL mode, the IT algorithm will take about 3 seconds to re-establish the correct battery capacity
and measurements, regardless of the total charge drawn in HIBERNATE mode. During this period of reestablishment, the gauge reports values previously calculated prior to entering HIBERNATE mode. The host can
identify exit from HIBERNATE mode by checking if Voltage() < Hibernate Voltage or [HIBERNATE] bit is cleared
by the gauge.
If a charger is attached, the host should immediately take the fuel gauge out of HIBERNATE mode before
beginning to charge the battery. Charging the battery in HIBERNATE mode will result in a notable gauging error
that will take several hours to correct. It is also recommended to minimize discharge current during exit from
Hibernate.
Note: The HIBERNATE mode is only available in I2C mode and is disabled when HDQ mode is used.
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POWER CONTROL
Reset Functions
When the bq27541-G1 detects a software reset by sending [RESET] Control( ) subcommand, it determines the
type of reset and increments the corresponding counter. This information is accessible by issuing the command
Control( ) function with the RESET_DATA subcommand.
Wake-Up Comparator
The wake up comparator is used to indicate a change in cell current while the bq27541-G1 is in SLEEP modes.
Pack Configuration uses bits [RSNS1-RSNS0] to set the sense resistor selection. Pack Configuration also
uses the [IWAKE] bit to select one of two possible voltage threshold ranges for the given sense resistor
selection. An internal interrupt is generated when the threshold is breached in either charge or discharge
directions. Setting both [RSNS1] and [RSNS0] to 0 disables this feature.
Table 21. IWAKE Threshold Settings (1)
(1)
IWAKE
RSNS1
RSNS0
Vth(SRP-SRN)
0
0
0
Disabled
1
0
0
Disabled
0
0
1
+1.0 mV or –1.0 mV
1
0
1
+2.2 mV or –2.2 mV
0
1
0
+2.2 mV or –2.2 mV
1
1
0
+4.6 mV or –4.6 mV
0
1
1
+4.6 mV or –4.6 mV
1
1
1
+9.8 mV or –9.8 mV
The actual resistance value vs the setting of the sense resistor is not important just the actual voltage
threshold when calculating the configuration. The voltage thresholds are typical values under room
temperature.
Flash Updates
Data Flash can only be updated if Voltage( ) ≥ Flash Update OK Voltage. Flash programming current can cause
an increase in LDO dropout. The value of Flash Update OK Voltage should be selected such that the bq27541G1 Vcc voltage does not fall below its minimum of 2.4V during Flash write operations.
AUTOCALIBRATION
The bq27541-G1 provides an autocalibration feature that will measure the voltage offset error across SRP and
SRN from time-to-time as operating conditions change. It subtracts the resulting offset error from normal sense
resistor voltage, VSR, for maximum measurement accuracy.
Autocalibration of the ADC begins on entry to SLEEP mode, except if Temperature( ) is ≤ 5°C or Temperature( )
≥ 45°C.
The fuel gauge also performs a single offset calibration when (1) the condition of AverageCurrent( ) ≤ 100mA
and (2) {voltage change since last offset calibration ≥ 256mV} or {temperature change since last offset calibration
is greater than 8°C for ≥ 60s}.
Capacity and current measurements will continue at the last measured rate during the offset calibration when
these measurements cannot be performed. If the battery voltage drops more than 32mV during the offset
calibration, the load current has likely increased considerably; hence, the offset calibration will be aborted.
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COMMUNICATIONS
AUTHENTICATION
The bq27541-G1 can act as a SHA-1/HMAC authentication slave by using its internal engine. Sending a 160-bit
SHA-1 challenge message to the bq27541-G1 will cause the gauge to return a 160-bit digest, based upon the
challenge message and a hidden, 128-bit plain-text authentication key. If this digest matches an identical one
generated by a host or dedicated authentication master, and when operating on the same challenge message
and using the same plain text keys, the authentication process is successful.
KEY PROGRAMMING (DATA FLASH KEY)
By default, the bq27541-G1 contains a default plain-text authentication key of
0x0123456789ABCDEFFEDCBA9876543210. This default key is intended for development purposes. It should
be changed to a secret key and the part immediately sealed, before putting a pack into operation. Once written, a
new plain-text key cannot be read again from the fuel gauge while in SEALED mode.
Once the bq27541-G1 is UNSEALED, the authentication key can be changed from its default value by writing to
the Authenticate( ) Extended Data Command locations. A 0x00 is written to BlockDataControl( ) to enable the
authentication data commands. The DataFlashClass() is issued 112 (0x70) to set the Security class. Up to 32
bytes of data can be read directly from the BlockData() (0x40...0x5f) and the authentication key is located at
0x48 (0x40 + 0x08 offset) to 0x57 (0x40 + 0x17 offset). The new authentication key can be written to the
corresponding locations (0x48 to 0x57) using the BlockData() command. The data is transferred to the data flash
when the correct checksum for the whole block (0x40 to 0x5f) is written to BlockDataChecksum() (0x60). The
checksum is (255- x) where x is the 8-bit summation of the BlockData() (0x40 to 0x5F) on a byte-by-byte basis .
Once the authentication key is written, the gauge can then be SEALED again.
KEY PROGRAMMING (THE SECURE MEMORY KEY)
As the name suggests, the bq27541-G1 secure-memory authentication key is stored in the secure memory of the
bq27541-G1. If a secure-memory key has been established, only this key can be used for authentication
challenges (the programmable data flash key is not available). The selected key can only be
established/programmed by special arrangements with TI, using the TI’s Secure B-to-B Protocol. The securememory key can never be changed or read from the bq27541-G1.
EXECUTING AN AUTHENTICATION QUERY
To execute an authentication query in UNSEALED mode, a host must first write 0x01 to the BlockDataControl( )
command, to enable the authentication data commands. If in SEALED mode, 0x00 must be written to
DataFlashBlock( ), instead.
Next, the host writes a 20-byte authentication challenge to the Authenticate( ) address locations (0x40 through
0x53). After a valid checksum for the challenge is written to AuthenticateChecksum( ), the bq27541-G1 uses the
challenge to perform the SHA-1/HMAC computation, in conjunction with the programmed key. The resulting
digest is written to AuthenticateData( ), overwriting the pre-existing challenge. The host may then read this
response and compare it against the result created by its own parallel computation.
HDQ SINGLE-PIN SERIAL INTERFACE
The HDQ interface is an asynchronous return-to-one protocol where a processor sends the command code to
the bq27541-G1. With HDQ, the least significant bit (LSB) of a data byte (command) or word (data) is transmitted
first. Note that the DATA signal on pin 12 is open-drain and requires an external pull-up resistor. The 8-bit
command code consists of two fields: the 7-bit HDQ command code (bits 0–6) and the 1-bit R/W field (MSB
bit 7). The R/W field directs the bq27541-G1 either to
• Store the next 8 or 16 bits of data to a specified register or
• Output 8 bits of data from the specified register
The HDQ peripheral can transmit and receive data as either an HDQ master or slave.
HDQ serial communication is normally initiated by the host processor sending a break command to the bq27541G1. A break is detected when the DATA pin is driven to a logic-low state for a time t(B) or greater. The DATA pin
should then be returned to its normal ready high logic state for a time t(BR). The bq27541-G1 is now ready to
receive information from the host processor.
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The bq27541-G1 is shipped in the I2C mode. TI provides tools to enable the HDQ peripheral. The SLUA408a
application report provides details of HDQ communication basics.
HDQ HOST INTERRUPTION FEATURE
The default bq27541-G1 behaves as an HDQ slave only device when HDQ mode is enabled. If the HDQ
interrupt function is enabled, the bq27541-G1 is capable of mastering and also communicating to a HDQ device.
There is no mechanism for negotiating who is to function as the HDQ master and care must be taken to avoid
message collisions. The interrupt is signaled to the host processor with the bq27541-G1 mastering an HDQ
"message". This message is a fixed message that will be used to signal the interrupt condition. The message
itself is 0x80 (slave write to register 0x00) with no data byte being sent as the command is not intended to
convey any status of the interrupt condition. The HDQ interrupt function is disabled by default and needs to be
enabled by command.
When the SET_HDQINTEN subcommand is received, the bq27541-G1 will detect any of the interrupt conditions
and assert the interrupt at one second intervals until the CLEAR_HDQINTEN command is received or the count
of HDQHostIntrTries has lapsed.
The number of tries for interrupting the host is determined by the data flash parameter named
HDQHostIntrTries.
Low Battery Capacity
This feature will work identically to SOC1. It will use the same data flash entries as SOC1 and will trigger
interrupts as long as SOC1 = 1 and HDQIntEN=1.
Temperature
This feature will trigger an interrupt based on the OTC (Over-Temperature in Charge) or OTD (Over-Temperature
in Discharge) condition being met. It uses the same data flash entries as OTC or OTD and will trigger interrupts
as long as either the OTD or OTC condition is met and HDQIntEN=1.
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I2C INTERFACE
The fuel gauge supports the standard I2C read, incremental read, one-byte write quick read, and functions. The
7-bit device address (ADDR) is the most significant 7 bits of the hex address and is fixed as 1010101. The 8-bit
device address is therefore 0xAA or 0xAB for write or read, respectively.
Host Generated
S
0 A
ADDR[6:0]
Fuel Gauge Generated
A
CMD[7:0]
A P
DATA[7:0]
S
1
ADDR[6:0]
A
(a)
S
ADDR[6:0]
0 A
DATA[7:0]
N P
(b)
CMD[7:0]
A Sr
1
ADDR[6:0]
A
DATA[7:0]
N P
...
DATA[7:0]
(c)
S
ADDR[6:0]
0 A
CMD[7:0]
A Sr
ADDR[6:0]
1
A
DATA[7:0]
A
N P
(d)
Figure 4. Supported I2C formats: (a) 1-byte write, (b) quick read, (c) 1 byte-read, and (d) incremental read
(S = Start, Sr = Repeated Start, A = Acknowledge, N = No Acknowledge, and P = Stop).
The "quick read" returns data at the address indicated by the address pointer. The address pointer, a register
internal to the I2C communication engine, increments whenever data is acknowledged by the bq27541-G1 or the
I2C master. "Quick writes" function in the same manner and are a convenient means of sending multiple bytes to
consecutive command locations (such as two-byte commands that require two bytes of data).
Attempt to write a read-only address (NACK after data sent by master):
S
ADDR[6:0]
0
A
A
CMD[7:0]
A
DATA[7:0]
P
Attempt to read an address above 0x7F (NACK command):
S
0
ADDR[6:0]
CMD[7:0]
A
N P
Attempt at incremental writes (NACK all extra data bytes sent):
S
ADDR[6:0]
0 A
CMD[7:0]
A
DATA[7:0]
A
DATA[7:0]
N
A
...
...
N P
Incremental read at the maximum allowed read address:
S
ADDR[6:0]
0 A
CMD[7:0]
A Sr
ADDR[6:0]
1
A
DATA[7:0]
Address
0x7F
Data From
addr 0x7F
DATA[7:0]
N P
Data From
addr 0x00
The I2C engine releases both SDA and SCL if the I2C bus is held low for t(BUSERR). If the fuel gauge was holding
the lines, releasing them frees the master to drive the lines. If an external condition is holding either of the lines
low, the I2C engine enters the low-power sleep mode.
I2C Time Out
The I2C engine will release both SDA and SCL if the I2C bus is held low for about 2 seconds. If the bq27541-G1
was holding the lines, releasing them will free for the master to drive the lines.
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I2C Command Waiting Time
To make sure the correct results of a command with the 400KHz I2C operation, a proper waiting time should be
added between issuing command and reading results. For subcommands, the following diagram shows the
waiting time required between issuing the control command the reading the status with the exception of the
checksum command. A 100ms waiting time is required between the checksum command and reading result. For
read-write standard commands, a minimum of 2 seconds is required to get the result updated. For read-only
standard commands, there is no waiting time required, but the host should not issue all standard commands
more than two times per second. Otherwise, the gauge could result in a reset issue due to the expiration of the
watchdog timer.
S
ADDR[6:0]
0 A
CMD[7:0]
A
DATA [7:0]
S
ADDR[6:0]
0 A
CMD[7:0]
A Sr
ADDR[6:0]
A
1 A
DATA [7:0]
A P
DATA [7:0]
66ms
A
DATA [7:0]
N P
A
DATA [7:0]
A
66ms
Waiting time between control subcommand and reading results
S
ADDR[6:0]
DATA [7:0]
0 A
A
CMD[7:0]
DATA [7:0]
A Sr
N P
ADDR[6:0]
1 A
DATA [7:0]
66ms
Waiting time between continuous reading results
I2C Clock Stretching
I2C clock stretches can occur during all modes of fuel gauge operation. In the SLEEP and HIBERNATE modes, a
short clock stretch will occur on all I2C traffic as the device must wake-up to process the packet. In NORMAL
and SLEEP+ modes, clock stretching will only occur for packets addressed for the fuel gauge. The timing of
stretches will vary as interactions between the communicating host and the gauge are asynchronous. The I2C
clock stretches may occur after start bits, the ACK/NAK bit and first data bit transmit on a host read cycle. The
majority of clock stretch periods are small (<= 4mSec) as the I2C interface peripheral and CPU firmware perform
normal data flow control. However, less frequent but more significant clock stretch periods may occur when data
flash (DF) is being written by the CPU to update the resistance (Ra) tables and other DF parameters such as
Qmax. Due to the organization of DF, updates need to be written in data blocks consisting of multiple data bytes.
An Ra table update requires erasing a single page of DF, programming the updated Ra table and a flag. The
potential I2C clock stretching time is 24ms max. This includes 20ms page erase and 2ms row programming time
(x2 rows). The Ra table updates occur during the discharge cycle and at up to 15 resistance grid points that
occur during the discharge cycle.
A DF block write typically requires a max of 72ms. This includes copying data to a temporary buffer and updating
DF. This temporary buffer mechanism is used to protect from power failure during a DF update. The first part of
the update requires 20ms time to erase the copy buffer page, 6 ms time to write the data into the copy buffer and
the program progress indicator (2ms for each individual write). The second part of the update is writing to the DF
and requires 44ms DF block update time. This includes a 20ms each page erase for two pages and 2ms each
row write for two rows.
In the event that a previous DF write was interrupted by a power failure or reset during the DF write, an
additional 44ms max DF restore time is required to recover the data from a previously interrupted DF write. In
this power failure recovery case, the total I2C clock stretching is 116ms max.
Another case where I2C clock stretches is at the end of discharge. The update to the last discharge data will go
through the DF block update twice because two pages are used for the data storage. The clock stretching in this
case is 144ms max. This occurs if there has been a Ra table update during the discharge.
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REFERENCE SCHEMATIC
J10
R20
4.7k
MM3511
3
5
4
6
2
1
R7, R8, and R9 are optional pull-down resistors if pull-up resistors are applied.
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PACKAGE OPTION ADDENDUM
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16-Jun-2012
PACKAGING INFORMATION
Orderable Device
Status
(1)
Package Type Package
Drawing
BQ27541DRZR-G1
PREVIEW
SON
BQ27541DRZT-G1
PREVIEW
SON
Pins
Package Qty
DRZ
12
3000
Green (RoHS
& no Sb/Br)
CU NIPDAU Level-2-260C-1 YEAR
DRZ
12
250
Green (RoHS
& no Sb/Br)
CU NIPDAU Level-2-260C-1 YEAR
Eco Plan
(2)
Lead/
Ball Finish
MSL Peak Temp
(3)
Samples
(Requires Login)
(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 - The planned eco-friendly classification: Pb-Free (RoHS), Pb-Free (RoHS Exempt), or Green (RoHS & no Sb/Br) - please check http://www.ti.com/productcontent for the latest availability
information and additional product content details.
TBD: The Pb-Free/Green conversion plan has not been defined.
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.
Pb-Free (RoHS Exempt): This component has a RoHS exemption for either 1) lead-based flip-chip solder bumps used between the die and package, or 2) lead-based die adhesive used between
the die and leadframe. The component is otherwise considered Pb-Free (RoHS compatible) as defined above.
Green (RoHS & no Sb/Br): TI defines "Green" to mean Pb-Free (RoHS compatible), and free of Bromine (Br) and Antimony (Sb) based flame retardants (Br or Sb do not exceed 0.1% by weight
in homogeneous material)
(3)
MSL, Peak Temp. -- The Moisture Sensitivity Level rating according to the JEDEC industry standard classifications, and peak solder temperature.
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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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