bq27425-G1
SLUSAI6 – NOVEMBER 2011
www.ti.com
System-Side Impedance Track™ Fuel Gauge With Integrated
Sense Resistor
FEATURES
APPLICATIONS
•
•
•
•
•
•
•
1
23
•
•
•
•
•
Battery Fuel Gauge for 1-Series LiCoO2 battery
Applications
Easy to Configure Battery Fuel Gauging Based
on Patented Impedance Track™ Technology
– Models Battery Discharge Curve for
Accurate State-of-Charge Report
– Automatically Adjusts for Battery Aging,
Battery Self-Discharge, and
Temperature/Rate Inefficiencies
– Low-Value Integrated Sense Resistor
(10 mΩ typical)
Resides on System Main Board
– Works with Embedded or Removable
Battery Packs
– Integrated LDO allows devices to be
powered directly from battery pack
Microcontroller Peripheral Provides:
– Accurate Battery Fuel Gauging
– Internal Temperature Sensor for Battery
Temperature Reporting
– Configurable Level of State-of-Charge
(SOC) Interrupts
2
I C™ for Connection to System
Microcontroller Port
Small 15-pin 2,69 × 1,75 mm, 0.5 mm pitch
CSP package
Feature Phones
Smart Phones
PDAs
Digital Still and Video Cameras
Handheld Terminals
MP3 or Multimedia Players
DESCRIPTION
The Texas Instruments bq27425 system-side LiCoO2
battery fuel gauge is an easy to configure
microcontroller peripheral that provides fuel gauging
for single-cell LiCoO2 battery packs. The device
requires minimal user configurations and system
microcontroller firmware development for accurate
fuel gauging.
The bq27425 uses the patented Impedance Track™
algorithm for fuel gauging, and provides information
such as remaining battery capacity (mAh),
state-of-charge (%), and battery voltage (mV).
Battery fuel gauging with the bq27425 requires only
PACK+ (P+), PACK– (P–), for a removable battery
pack or embedded battery circuit. The 15-pin 2,69 ×
1,75 mm, 0.5 mm pitch CSP package is ideal for
space constrained applications.
TYPICAL APPLICATION
Single Cell Li- Ion
Battery Pack
Voltage
Sense
VBAT
VCC
LDO
System
Interface
I2C
bq27425
PROTECTION
IC
To Charger
T
DATA
SRX
GPOUT
BIN
PACK +
REGIN
Integrated
Current
Sense
PACK -
FETs
CHG
DSG
VSS
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 Phillips 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, Texas Instruments Incorporated
bq27425-G1
SLUSAI6 – NOVEMBER 2011
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
PART NUMBER
PACKAGE (1)
TA
COMMUNICATION
FORMAT
CSP-15
–40°C to 85°C
I2C
bq27425YZFR-G1
bq27425YZFT-G1
(1)
TAPE and REEL
QUANTITY
3000
250
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.
PIN DIAGRAM
CSP-15
(BOTTOM VIEW)
CSP-15
(TOP VIEW)
A3
B3
C3
D3
E3
E3
D3
C3
B3
A3
A2
B2
C2
D2
E2
E2
D2
C2
B2
A2
A1
B1
C1
D1
E1
E1
D1
C1
B1
A1
PIN FUNCTIONS
PIN
NAME
NO.
TYPE (1)
DESCRIPTION
Integrated Sense Resistor and Coulomb Counter input typically connected to battery PACK- terminal. For best
performance decouple with 0.1μF ceramic capacitor to Vss.
SRX
B1
IA
VSS
C1
P, IA
VCC
D1
P
Regulator output and bq27425 processor power. Decouple with 1μF ceramic capacitor to Vss.
REGIN
E1
P
Regulator input. Decouple with 0.1μF ceramic capacitor to Vss.
CE
D2
I
Chip Enable. Internal LDO is disconnected from REGIN when driven low.
BAT
E2
I
Cell-voltage measurement input. ADC input. Recommend 4.8V maximum for conversion accuracy.
SCL
A3
I
Slave I2C serial communications clock input line for communication with system (Master). Use with 10kΩ pull-up
resistor (typical).
SDA
B3
I/O
Slave I2C serial communications data line for communication with system (Master). Open-drain I/O. Use with 10kΩ
pull-up resistor (typical).
BIN
C3
I
Battery-insertion detection input. A logic high to low transition is detected as a battery insertion event. Recommend
using a pull-up resistor >1MΩ (1.8 MΩ typical) to VCC for reduced power consumption. An internal pull-up resistor
option is also available using the Operation Configuration[BI_PU_EN] register bit.
GPOUT
A2
O
General Purpose open-drain output. May be configured as a Battery Low indicator or perform SOC interrupt
(SOC_INT) function.
A1, B2,
C2, D3,
E3
IA
No Connect.
NC
(1)
2
Device ground and Integrated Sense Resistor termination.
I/O = Digital input/output, IA = Analog input, P = Power connection
Copyright © 2011, Texas Instruments Incorporated
bq27425-G1
SLUSAI6 – NOVEMBER 2011
www.ti.com
ELECTRICAL SPECIFICATIONS
ABSOLUTE MAXIMUM RATINGS
over operating free-air temperature range (unless otherwise noted) (1)
VALUE
UNIT
VREGIN
Regulator input range
PARAMETER
–0.3 to 5.5
V
VCC
Supply voltage range
–0.3 to 2.75
V
VIOD
Open-drain I/O pins (SDA, SCL)
–0.3 to 5.5
V
VBAT
BAT input pin
–0.3 to 5.5
VI
Input voltage range to all other pins (SRX , GPOUT)
TA
Tstg
(1)
–0.3 to VCC + 0.3
V
Operating free-air temperature range
–40 to 85
°C
Storage temperature range
–65 to 150
°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
Value
THERMAL METRIC (1)
θJA
Junction-to-ambient thermal resistance
70
θJCtop
Junction-to-case (top) thermal resistance
17
θJB
Junction-to-board thermal resistance
20
ψJT
Junction-to-top characterization parameter
1
ψJB
Junction-to-board characterization parameter
18
θJCbot
Junction-to-case (bottom) thermal resistance
n/a
(1)
UNITS
YZF(15 PINS)
°C/W
For more information about traditional and new thermal metrics, see the IC Package Thermal Metrics application report, SPRA953
RECOMMENDED OPERATING CONDITIONS
TA = 25°C and VREGIN = VBAT = 3.6V (unless otherwise noted)
PARAMETER
TEST CONDITIONS
No operating restrictions
VREGIN
Supply voltage
CREGIN
External input capacitor for internal LDO between
REGIN and VSS
CLDO25
External output capacitor for internal LDO between
VCC and VSS
ICC
NORMAL operating-mode current (1)
Fuel gauge in NORMAL mode.
ILOAD > Sleep Current
ISLP
SLEEP mode operating mode current (1)
Fuel gauge in SLEEP mode.
ILOAD < Sleep Current
IHIB
Hibernate operating-mode current (1)
Fuel gauge in HIBERNATE mode.
ILOAD < Hibernate Current
VOL(OD)
Output low voltage on open-drain pins (SCL, SDA,
GPOUT)
IOL = 1 mA
VOH(OD)
Output high voltage on open-drain pins (SDA, SCL,
GPOUT)
VIL
Input low voltage, all digital pins
No NVM writes
Input high voltage (SDA, SCL)
VIH
Input high voltage (BIN)
VA2
Input voltage range (BAT)
VA3
Input voltage range (SRX)
(1)
(2)
(1) (2)
Nominal capacitor values specified.
Recommend a 5% ceramic X5R type
capacitor located close to the device.
External pullup resistor connected to VCC
MIN
TYP
MAX
2.7
4.5
2.45
2.7
0.47
UNIT
V
0.1
μF
1
μF
118
μA
23
μA
8
μA
0.4
VCC – 0.5
V
V
–0.3
0.6
V
1.2
5.5
V
1.2
VCC +
0.3
V
VSS – 0.125
5
V
VSS – 0.040
0.040
V
Specified by design. Not production tested.
Limited by ISRX maximum recommend input current with some margin for the Integrated Sense Resistor tolerance
Copyright © 2011, Texas Instruments Incorporated
3
bq27425-G1
SLUSAI6 – NOVEMBER 2011
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RECOMMENDED OPERATING CONDITIONS (continued)
TA = 25°C and VREGIN = VBAT = 3.6V (unless otherwise noted)
PARAMETER
Ilkg
Input leakage current (I/O pins)
tPUCD
Power-up communication delay
TEST CONDITIONS
MIN
TYP
MAX
0.3
250
UNIT
μA
ms
POWER-ON RESET
TA = –40°C to 85°C, typical values at TA = 25°C and VREGIN = 3.6 V (unless otherwise noted)
PARAMETER
TEST CONDITIONS
VIT+
Positive-going voltage on VCC (Regulator output)
VHYS
Power-on reset hysteresis
MIN
TYP
MAX
1.98
2.20
2.31
UNIT
V
43
115
185
mV
UNIT
2.5V LDO REGULATOR
TA = 25°C, CLDO25 = 1μF, VREGIN = 3.6 V (unless otherwise noted)
PARAMETER
TEST CONDITION
MIN
NOM
MAX
2.5
2.6
2.5 V LDO REGULATOR (1)
VREG25
Regulator output voltage
VIH(CE)
CE High-level input
voltage
VIL(CE)
CE Low-level input
voltage
VDO
Regulator dropout voltage
ΔVREGTEMP
ΔVREGLINE
ΔVREGLOAD
ISHORT
(1)
(2)
4
(2)
2.7V ≤ VREGIN ≤ 4.5V, IOUT ≤ 5mA
TA = –40°C to 85°C
2.4
2.45V ≤ VREGIN < 2.7V (low battery),
IOUT ≤ 3mA
TA = –40°C to 85°C
2.4
VREGIN = 2.7 to 4.5V
TA = –40°C to 85°C
V
2.65
V
0.8
2.7V, IOUT ≤ 5mA
TA = –40°C to 85°C
325
2.45V, IOUT ≤ 3mA
TA = –40°C to 85°C
50
Regulator output change
with temperature
VREGIN = 3.6V, IOUT = 5mA
TA = –40°C to 85°C
Line regulation
2.7V ≤ VREGIN ≤ 4.5V, IOUT = 5mA
18
40
0.2mA ≤ IOUT ≤ 3mA, VREGIN = 2.45 V
34
40
3mA ≤ IOUT ≤ 5mA, VREGIN = 2.7 V
31
Load regulation
Short circuit current limit
V
VREG25 = 0V
TA = –40°C to 85°C
mV
0.5%
250
mV
mV
mA
LDO output current, IOUT, is the sum of internal and external load currents.
Assured by design. Not production tested.
Copyright © 2011, Texas Instruments Incorporated
bq27425-G1
SLUSAI6 – NOVEMBER 2011
www.ti.com
INTERNAL TEMPERATURE SENSOR CHARACTERISTICS
TA = –40°C to 85°C; typical values at TA = 25°C and VREGIN = 3.6 V (unless otherwise noted)
PARAMETER
GTEMP
TEST CONDITIONS
MIN
TYP
MAX
UNIT
–2
Temperature sensor voltage gain
mV/°C
INTEGRATING ADC (COULOMB COUNTER) CHARACTERISTICS
TA = –40°C to 85°C; typical values at TA = 25°C and VREGIN = 3.6 V (unless otherwise noted)
PARAMETER
VSR
Input voltage range
tSR_CONV
Conversion time
TEST CONDITIONS
(1) (2)
VSR = V(SRX) – VSS
MIN
Single conversion
Input offset
INL
Integral nonlinearity error
ZIN(SR)
Effective input resistance (1)
Ilkg(SR)
Input leakage current (1)
UNIT
V
s
14
VOS(SR)
MAX
0.040
1
Resolution
(1)
(2)
TYP
–0.040
15
bits
μV
10
±0.007
±0.034
2.5
% FSR
MΩ
TA = 25°C
0.3
μA
Specified by design. Not tested in production.
Limited by ISRX maximum recommend input current with some margin for the Integrated Sense Resistor tolerance.
INTEGRATED SENSE RESISTOR CHARACTERISTICS
TA = –40°C to 85°C; typical values at TA = 25°C and VREGIN = 3.6 V (unless otherwise noted)
PARAMETER
TEST CONDITIONS
MIN
TYP
MAX
SRXRES
Resistance of Integrated Sense Resistor from SRX
to VSS. (1) (2)
TA = 25°C
ISRX
Recommended Sense Resistor input current. (1) (3)
Long term RMS, average
device utilization.
1000
mA
Peak RMS current, 10%
device utilization. (3)
2500
mA
Peak pulsed current, 250mS
max, 1% device utilization. (3)
3500
mA
MAX
UNIT
(1)
(2)
(3)
10
UNIT
mΩ
Specified by design. Not tested in production.
Firmware compensation applied for temperature coefficient of resistor.
Device utilization is the long term usage profile at a specific condition compared to the average condition.
ADC (TEMPERATURE AND CELL MEASUREMENT) CHARACTERISTICS
TA = –40°C to 85°C; typical values at TA = 25°C and VREGIN = 3.6 V (unless otherwise noted)
PARAMETER
VIN(ADC)
Input voltage range
tADC_CONV
Conversion time
TEST CONDITIONS
Resolution
VOS(ADC)
Effective input resistance (BAT) (1)
Ilkg(ADC)
Input leakage current (1)
TYP
1
14
Input offset
ZADC
(1)
MIN
0.05
ms
15
bits
1
Not measuring cell voltage
Measuring cell voltage
TA = 25°C
V
125
mV
8
MΩ
100
kΩ
0.3
μA
Specified by design. Not tested in production.
Copyright © 2011, Texas Instruments Incorporated
5
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EEPROM MEMORY CHARACTERISTICS
TA = –40°C to 85°C; typical values at TA = 25°C and VREGIN = 3.6 V (unless otherwise noted)
PARAMETER
TEST CONDITIONS
MIN
TYP
Array Size
256
Data retention (1)
Programming write cycles (1)
(1)
MAX
UNIT
Bytes
10
Years
100K
Cycles
Specified by design. Not production tested
I2C-COMPATIBLE INTERFACE COMMUNICATION TIMING CHARACTERISTICS
TA = –40°C to 85°C; typical values at TA = 25°C and VREGIN = 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 duration (high)
600
ns
tw(L)
SCL pulse duration (low)
1.3
μs
tsu(STA)
Setup for repeated start
600
ns
td(STA)
Start to first falling edge of SCL
600
ns
tsu(DAT)
Data setup time
100
ns
th(DAT)
Data hold time
0
ns
tsu(STOP)
Setup time for stop
t(BUF)
Bus free time between stop and start
fSCL
Clock frequency
600
ns
66
μs
400
tSU(STA)
tw(H)
tf
tw(L)
tr
kHz
t(BUF)
SCL
SDA
td(STA)
tsu(STOP)
tf
tr
REPEATED
START
th(DAT)
tsu(DAT)
STOP
START
Figure 1. I2C-Compatible Interface Timing Diagrams
6
Copyright © 2011, Texas Instruments Incorporated
bq27425-G1
SLUSAI6 – NOVEMBER 2011
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GENERAL DESCRIPTION
The bq27425 accurately predicts the battery capacity and other operational characteristics of a single LiCoO2
rechargeable cell. It can be interrogated by a system processor to provide cell information, such as
state-of-charge (SOC).
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 bq27425 control and status registers,
as well as its data locations. Commands are sent from system to gauge using the bq27425’s I2C serial
communications engine, and can be executed during application development, pack manufacture, or
end-equipment operation.
The key to the bq27425’s high-accuracy gas gauging prediction is Texas Instrument’s proprietary Impedance
Track™ algorithm. This algorithm uses cell measurements, characteristics, and properties to create
state-of-charge predictions that can achieve high accuracy across a wide variety of operating conditions and over
the lifetime of the battery.
The bq27425 measures charge/discharge activity by monitoring the voltage across a small-value integrated
sense resistor (10 mΩ typical) located between the system’s Vss and the battery’s PACK– terminal. When a cell
is attached to the bq27425, cell impedance is computed, based on cell current, cell open-circuit voltage (OCV),
and cell voltage under loading conditions.
The bq27425 utilizes an integrated temperature sensor for estimating cell temperature. Alternatively, the host
processor can provide temperature data for the bq27425.
To minimize power consumption, the bq27425 has several power modes: INITIALIZATION, NORMAL, SLEEP,
and HIBERNATE. The bq27425 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
RemainingCapacity( ).
NVM Data: italics, bold, and breaking spaces, e.g. Design Capacity.
Register bits and flags: brackets and italics, e.g. [TDA]
NVM Data bits: brackets, italics and bold, e.g: [LED1]
Modes and states: ALL CAPITALS, e.g. UNSEALED mode.
Copyright © 2011, Texas Instruments Incorporated
spaces,
e.g.
7
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SLUSAI6 – NOVEMBER 2011
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DATA COMMANDS
Standard Data Commands
The bq27425 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. Because
each command consists of two bytes of data, two consecutive I2C transmissions must be executed both to
initiate the command function, and to read or write the corresponding two bytes of data. Additional options for
transferring data, such as spooling, are described in Section, I2C INTERFACE. Standard commands are
accessible in NORMAL operation. Read/Write permissions depend on the active access mode, SEALED or
UNSEALED (for details on the SEALED and UNSEALED states, refer to Section Access Modes.)
Table 1. Standard Commands
COMMAND CODE
UNITS
SEALED ACCESS
Control( )
NAME
CNTL
0x00 / 0x01
N/A
R/W
Temperature( )
TEMP
0x02 / 0x03
0.1°K
R/W
Voltage( )
VOLT
0x04 / 0x05
mV
R
FLAGS
0x06 / 0x07
N/A
R
NominalAvailableCapacity( )
NAC
0x08 / 0x09
mAh
R
FullAvailableCapacity( )
FAC
0x0a / 0x0b
mAh
R
RemainingCapacity( )
RM
0x0c / 0x0d
mAh
R
FullChargeCapacity( )
FCC
0x0e / 0x0f
mAh
R
AverageCurrent( )
AI
0x10 / 0x11
mA
R
StandbyCurrent( )
SI
0x12 / 0x13
mA
R
MaxLoadCurrent( )
MLI
0x14 / 0x15
mA
R
AveragePower( )
AP
0x18 / 0x19
mW
R
StateOfCharge( )
SOC
0x1c / 0x1d
%
R
IntTemperature( )
ITEMP
0x1e / 0x1f
0.1°K
R
SOH
0x20 / 0x21
%
R
Flags( )
StateofHealth( )
8
Copyright © 2011, Texas Instruments Incorporated
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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
bq27425 during normal operation and additional features when the bq27425 is in different access modes, as
described in Table 2.
Table 2. Control( ) Subcommands
CNTL FUNCTION
CNTL DATA
SEALED ACCESS
CONTROL_STATUS
0x0000
Yes
Reports the status of device.
DEVICE_TYPE
0x0001
Yes
Reports the device type (0x0410).
FW_VERSION
0x0002
Yes
Reports the firmware version on the device type.
HW_VERSION
0x0003
Yes
Reports the hardware version of the device type.
PREV_MACWRITE
0x0007
No
Returns previous MAC command code.
BAT_INSERT
0x000c
Yes
Forces the [BAT_DET] bit set when the [BIE] bit is 0.
BAT_REMOVE
0x000d
Yes
Forces the [BAT_DET] bit clear when the [BIE] bit is 0.
SET_HIBERNATE
0x0011
Yes
Forces CONTROL_STATUS [HIBERNATE] to 1.
CLEAR_HIBERNATE
0x0012
Yes
Forces CONTROL_STATUS [HIBERNATE] to 0.
SET_CFGUPDATE
0x0013
No
Force CONTROL_STATUS [CFGUPMODE] to 1 and gauge enters
CONFIG UPDATE mode.
SEALED
0x0020
No
Places the bq27425 in SEALED access mode.
RESET
0x0041
No
Forces a full reset of the bq27425.
SOFT_RESET
0x0042
No
Performs a soft reset to reinitialize configuration data. Forces
CONTROL_STATUS [CFGUPMODE] to 0.
Copyright © 2011, Texas Instruments Incorporated
DESCRIPTION
9
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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 Bit Definitions
bit7
bit6
bit5
bit4
bit3
bit2
bit1
bit0
High Byte
RSVD
RSVD
SS
CALMODE
CCA
BCA
QMAX_UP
RES_UP
Low Byte
RSVD
HIBERNATE
RSVD
SLEEP
LDMD
RUP_DIS
VOK
RSVD
RSVD = Reserved.
SS = Status bit indicating the bq27425 is in the SEALED State. Active when set.
CALMODE = Status bit indicating the bq27425 is in calibration mode. Active when set.
CCA =
Status bit indicating the bq27425 Coulomb Counter Auto-Calibration routine is active. The CCA routine will take place
approximately 3 minutes and 45 seconds after the initialization. Active when set.
BCA = Status bit indicating the bq27425 board calibration routine is active. Active when set.
QMAX_UP =
Status bit indicating Qmax has Updated. True when set. This bit is cleared after power on reset or when [BAT_DET] bit is
set. When this bit is cleared, it enables fast learning of battery Qmax.
Status bit indicating that resistance has been updated. True when set. This bit is cleared after power on reset or when
RES_UP = [BAT_DET] bit is set. Also this bit can only be set after Qmax is updated or QMAXU is set. When this bit is cleared, it
enables fast learning of battery impedance.
HIBERNATE = Status bit indicating a request for entry into HIBERNATE from SLEEP mode has been issued. True when set. Default is 0.
SLEEP = Status bit indicating the bq27425 is in SLEEP mode. True when set.
LDMD =
Status bit indicating the algorithm is using constant-power mode. True when set. Default is 1. Note: The bq27425 always
uses constant-power mode.
RUP_DIS = Status bit indicating the bq27425 Ra table updates are disabled. Updates disabled when set..
VOK = Status bit indicating cell voltages are OK for Qmax updates. True when set.
DEVICE_TYPE: 0x0001
Instructs the fuel gauge to return the device type to addresses 0x00/0x01.
FW_VERSION: 0x0002
Instructs the fuel gauge to return the firmware version to addresses 0x00/0x01.
HW_VERSION: 0x0003
Instructs the fuel gauge to return the hardware version to addresses 0x00/0x01.
PREV_MACWRITE: 0x0007
Instructs the fuel gauge to return the previous command written to addresses 0x00/0x01. The value returned is
limited to less than 0x0015.
BAT_INSERT: 0X000C
This subcommand forces the Flags() [BAT_DET] bit to set when the battery insertion detection is disabled via
OpConfig[BIE=0]. In this case, the gauge does not detect battery insertion from the BIN pin’s logic state, but
relies on the BAT_INSERT host subcommand to indicate battery presence in the system. This subcommand also
starts Impedance Track™ gauging.
BAT_REMOVE: 0X000D
This subcommand forces the Flags() [BAT_DET] bit to clear when the battery insertion detection is disabled via
OpConfig[BIE=0]. In this case, the gauge does not detect battery removal from the BIN pin’s logic state, but
relies on the BAT_REMOVE host subcommand to indicate battery removal from the system.
10
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SLUSAI6 – NOVEMBER 2011
SET_HIBERNATE: 0x0011
Instructs the fuel gauge to force the CONTROL_STATUS[HIBERNATE] bit to 1. This allows the gauge to enter
the HIBERNATE power mode after the transition to SLEEP power state is detected. The [HIBERNATE] bit is
automatically cleared upon exiting from HIBERNATE mode.
CLEAR_HIBERNATE: 0x0012
Instructs the fuel gauge to force the CONTROL_STATUS[HIBERNATE] and [HIBE] bit to 0. This prevents the
gauge from entering the HIBERNATE power mode after the transition to SLEEP power state is detected. It can
also be used to force the gauge out of HIBERNATE mode.
SET_CFGUPDATE: 0x0013
Instructs the fuel gauge to set the CONTROL_STATUS[CFGUPMODE] bit to 1 and enter CONFIG UPDATE
mode. This command is only available when the fuel gauge is UNSEALED. Note: A SOFT_RESET subcommand
is typically used to exit CONFIG UPDATE mode for use resume normal gauging.
FACTORY_RESTORE: 0X0015
Instructs the fuel gauge to reset learned resistance tables and Qmax values (default = DesignCapacity) to the
default values. This command is only available when the fuel gauge is UNSEALED.
SEALED: 0x0020
Instructs the fuel gauge to transition from UNSEALED state to SEALED state. The fuel gauge should always be
set to SEALED state for use in end equipment.
RESET : 0x0041
This command instructs the fuel gauge to perform a full device reset and reset RAM data to the default values
from ROM. This command is only available when the fuel gauge is UNSEALED.
SOFT_RESET : 0x0042
This command instructs the fuel gauge to perform a partial reset to reinitialize configuration data and clear the
ITPOR bit of the Flags( ) register to resume normal gauging from CONFIG UPDATE mode. This command is
only available when the fuel gauge is UNSEALED.
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Temperature( ): 0x02/0x03
This read-/write-word function returns an unsigned integer value of the temperature in units of 0.1 K measured by
the fuel gauge. If [TEMPS] bit = 1, a write command sets the temperature to be used for gauging calculations
while a read command returns to temperature previously written. If [TEMPS] bit = 0, a read command will return
the internal temperature sensor value and write command will be ignored.
Voltage( ): 0x04/0x05
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( ): 0x06/0x07
This read-word 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
OT
UT
RSVD
RSVD
RSVD
EEFAIL
FC
CHG
Low Byte
OCVTAKEN
RSVD
ITPOR
CFGUPMODE
BAT_DET
SOC1
SOCF
DSG
OT = Over-Temperature condition is detected. True when set. See Over-Temperature Indication: Charge Sub-Section.
UT = Under-Temperature condition is detected. True when set. See Over-Temperature Indication: Discharge Sub-Section.
RSVD = Reserved.
RSVD = Reserved.
RSVD = Reserved.
EEFAIL = EEPROM Write Fail. True when set. This bit is set after a single EEPROM write failure. All subsequent EEPROM writes
are disabled. A power on reset or RESET subcommand is required to clear the bit to re-enable EEPROM writes.
FC = Full-charged condition reached. 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
RSVD = Reserved.
ITPOR =
Indicates a Power On Reset or RESET subcommand as occurred. True when set. This bit is cleared after the
SOFT_RESET subcommand is received.
CFGUPMODE = Fuel gauge is in CONFIG UPDATE mode. True when set. Default is 0. Refer to CONFIG Mode section for details.
Battery insertion detected. True when set. When OpConfig[BIE]] is set, [BAT_DET] is set by detecting a logic high to low
BAT_DET = transition at BIN pin. when OpConfig[BIE]] is low, [BAT_DET] is set when host issues BAT_INSERT subcommand and
clear when host issues BAT_REMOVE subcommand.
SOC1 =
If set, StateOfCharge() = SOC1 Clear
Threshold.
SOCF =
If set, StateOfCharge() = SOCF Clear
Threshold.
DSG = Discharging detected. True when set.
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NominalAvailableCapacity( ): 0x08/0x09
This read-only command pair returns the uncompensated (less than C/20 load) battery capacity remaining. Units
are mAh.
FullAvailableCapacity( ): 0x0a/0x0b
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( ): 0x0c/0x0d
This read-only command pair returns the compensated battery capacity remaining. Units are mAh.
FullChargeCapacity( ): 0x0e/0f
This read-only command pair returns the compensated capacity of the battery when fully charged. Units are
mAh. FullChargeCapacity( ) is updated at regular intervals, as specified by the IT algorithm.
AverageCurrent( ): 0x10/0x11
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.
StandbyCurrent( ): 0x12/0x13
This read-only function returns a signed integer value of the measured standby current through the sense
resistor. The StandbyCurrent( ) is an adaptive measurement. Initially it reports the standby current programmed
in Initial Standby (default = -10mA), 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 ( = ±5mA) and
is less than or equal to 2 x Initial Standby (default = -10mA). 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.
MaxLoadCurrent( ): 0x14/0x15
This read-only function returns a signed integer value, in units of mA, of the maximum load conditions. The
MaxLoadCurrent( ) is an adaptive measurement which is initially reported as the maximum load current
programmed in Initial Max Load Current (default = –500mA) . 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.
AveragePower( ): 0x18/0x19
This read-only function returns an signed integer value of the average power during battery charging and
discharging. 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.
StateOfCharge( ): 0x1c/0x1d
This read-only function returns an unsigned integer value of the predicted remaining battery capacity expressed
as a percentage of FullChargeCapacity( ), with a range of 0 to 100%.
IntTemperature( ): 0x1e/0x1f
This read-/write-word function returns an unsigned integer value of the internal temperature sensor in units of 0.1
K measured by the fuel gauge. If OpConfig[WRTEMP] = 0, this command will return the same value as
Temperature( ).
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StateofHealth( ): 0x20/0x21
0x20 SOH percentage: this read-only function returns an unsigned integer value, expressed as a percentage of
the ratio of predicted FCC(25°C, SOH LoadI) over the DesignCapacity(). The FCC(25°C, SOH LoadI) is the
calculated full charge capacity at 25°C and the SOH LoadI which is programmed in factory (default = –400mA).
The range of the returned SOH percentage is 0x00 to 0x64, indicating 0 to 100% correspondingly.
0x21 SOH Status: this read-only function returns an unsigned integer value, indicating the status of the SOH
percentage. The meanings of the returned value are:
• 0x00: SOH not valid (initialization)
• 0x01: Instant SOH value ready
• 0x02: Initial SOH value ready
– Calculation based on uncompensated Qmax
– Updated at first grid point update after cell insertion
• 0x03: SOH value ready
– Utilize the updated Qmax update
– Calculation based on compensated Qmax
– Updated after complete charge and relax is complete
• 0x04-0xFF: Reserved
14
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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.
Table 5. Extended Commands
NAME
OperationConfiguration( )
DesignCapacity( )
COMMAND CODE
UNITS
SEALED
ACCESS (1) (2)
UNSEALED
ACCESS (1) (2)
OPCFG
0x3a / 0x3b
N/A
R
R/W
DCAP
0x3c / 0x3d
mAh
R
R/W
0x3e
N/A
N/A
R/W
DataClass( )
(2)
DFCLS
DataBlock( )
(2)
DFBLK
0x3f
N/A
R/W
R/W
DFD
0x40…0x5f
N/A
R
R/W
DFDCKS
0x60
N/A
R/W
R/W
BlockData( )
BlockDataCheckSum( )
BlockDataControl( )
DeviceNameLength( )
DeviceName( )
Reserved
(1)
(2)
DFDCNTL
0x61
N/A
N/A
R/W
DNAMELEN
0x62
N/A
R
R
DNAME
0x63...0x69
N/A
R
R
RSVD
0x6a...0x7f
N/A
R
R
SEALED and UNSEALED states are entered via commands to Control( ) 0x00/0x01
In sealed mode, data CANNOT be accessed through commands 0x3e and 0x3f.
OperationConfiguration( ): 0x3a/0x3b
SEALED and UNSEALED Access: This command returns the Operation Configuration register setting
DesignCapacity( ): 0x3c/0x3d
SEALED and UNSEALED Access: This command returns the value is stored in Design Capacity and is
expressed in mAh. This is intended to be the theoretical or nominal capacity of a new pack and is used as an
input for the algorithm to scale the normalized resistance tables.
DataClass( ): 0x3e
UNSEALED Access: This command sets the data class to be accessed. The class to be accessed should be
entered in hexadecimal.
SEALED Access: This command is not available in SEALED mode.
DataBlock( ): 0x3f
UNSEALED Access: This command sets the data block to be accessed. When 0x00 is written to
BlockDataControl( ), DataBlock( ) holds the block number of the data to be read or written. Example: writing a
0x00 to DataBlock( ) 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 block will be accessed by the BlockData( ) command.
Issuing a 0x01 instructs the BlockData( ) command to transfer Manufacturer Info Block A.
BlockData( ): 0x40…0x5f
UNSEALED Access: This data block is the remainder of the 32 byte data block when accessing general block
data.
SEALED Access: This data block is the remainder of the 32 byte data block when accessing Manufacturer Info
Block.
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BlockDataChecksum( ): 0x60
UNSEALED Access: This byte contains the checksum on the 32 bytes of block data read or written. The
least-significant byte of the sum of the data bytes written must be complemented ( [255 – x] , for x the
least-significant byte) before being written to 0x60.
SEALED Access: This byte contains the checksum for the 32 bytes of block data written to Manufacturer Info
Block. The least-significant byte of the sum of the data bytes written must be complemented ( [255 – x] , for x
the least-significant byte) before being written to 0x60.
BlockDataControl( ): 0x61
UNSEALED Access: This command is used to control the data access mode. Writing 0x00 to this command
enables BlockData( ) to access general data NVM. Writing a 0x01 to this command enables SEALED mode
operation of DataBlock( ).
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…0x69
UNSEALED and SEALED Access: This block contains the device name that is programmed in Device Name
Reserved – 0x6a – 0x7f
BLOCK DATA INTERFACE
Accessing Block Data
The bq27425 contains both re-writable EEPROM non-volatile memory (NVM) and ROM-based data blocks. Upon
device RESET, the ROM-based data blocks are copied to associated volatile RAM space to initialize default
configuration and data constants to be used by the fuel gauging algorithm. Re-writable NVM-based data blocks
contain information expected to change such as: calibration, customer data and Impedance Track fuel gauging
data tables. If the application requires a change to the NVM or RAM configuration data, the host can update the
data blocks in CONFIG UPDATE mode. RAM-based data changes are temporary and must be applied by the
host using CONFIG UPDATE mode after each device RESET; while changes to the NVM data blocks are
permanent. The data blocks can be accessed in several different ways, depending on the access mode and what
data is being accessed.
Commonly accessed data block locations, frequently read by a system, are conveniently accessed through
specific instructions, already described in Section Data Commands. These commands are available when the
bq27425 is either in UNSEALED or SEALED modes.
Most data block locations, however, are only accessible in UNSEALED mode by use of the bq27425 evaluation
software or by data 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 locations individually, the block containing the desired data NVM 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 the associated data block, once the correct checksum for the whole block is written to
BlockDataChecksum( ) (0x60).
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Occasionally, a data CLASS will be larger than the 32-byte block size. In this case, the DataBlock( ) 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,
DataClass( ) is issued 80 (0x50) to set the class. Because the offset is 48, it must reside in the second 32-byte
block. Hence, DataBlock( ) is issued 0x01 to set the block offset, and the offset used to index into the
BlockData( ) memory area is 0x40 + 48 modulo 32 = 0x40 + 16 = 0x40 + 0x10 = 0x50.
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 bq27425, 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 data written to NVM blocks is persistent, so a power-on reset does not resolve the fault.
ACCESS MODES
The bq27425 provides three security modes (FULL ACCESS, UNSEALED, and SEALED) that control data NVM
access permissions according to Table 6. Although FULL ACCESS and UNSEALED modes appear identical,
only FULL ACCESS mode allows the bq27425 to write access-mode transition keys.
Table 6. Data NVM Access
Security Mode
Data NVM
Manufacturer Info
FULL ACCESS
R/W
R/W
UNSEALED
R/W
R/W
SEALED
None
R
SEALING/UNSEALING DATA BLOCKS
The bq27425 implements a key-access scheme to transition between SEALED, UNSEALED, and
FULL-ACCESS modes. Each transition requires that a unique set of two keys be sent to the bq27425 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.
When in SEALED mode the [SS] bit of CONTROL_STATUS is set, but when the UNSEAL keys are correctly
received by the bq27425, the [SS] bit is cleared. When the full-access keys are correctly received then the
CONTROL_STATUS [FAS] bit is cleared.
Both the sets of keys for each level are 2 bytes each in length and are stored in data ROM. The UNSEAL key
(stored at Unseal Key 0 and Unseal Key 1) and the FULL-ACCESS key (stored at Full Access Key 0 and Full
Access Key 1) can only be updated when in FULL-ACCESS mode. The order of the bytes entered through the
Control( ) command is the reverse of what is read from the part. For example, if the 1st and 2nd word of the
UnSeal Key 0 returns 0x1234 and 0x5678, then Control( ) should supply 0x3412 and 0x7856 to unseal the part.
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BLOCK DATA SUMMARY
Table 7 summarizes the data blocks available to the user, including their default, minimum, and maximum
values.
Table 7. Block Data Summary
Class
Configuration
[RAM]
SubClass
ID
SubClass
Offset
2
Safety [RAM]
0
Over Temp
2
4
36
49
68
Charge
Termination
[RAM]
Discharge
[RAM]
Power [RAM]
Name
Data
Type
Min
Max
Default
Unit
(EVSW Unit)
I2
-1200
1200
550
0.1°C
Under Temp
I2
-1200
1200
0
0.1°C
Temp Hys
U1
0
255
50
0.1°C
0
Min Taper Capacity
I2
0
1000
25
mAh
2
Current Taper
Window
U1
0
60
40
mV
3
TCA Set %
I1
-1
100
99
%
4
TCA Clear %
I1
-1
100
95
%
5
FC Set %
I1
-1
100
100
%
6
FC Clear %
I1
-1
100
98
%
0
SOC1 Set Threshold
U1
0
255
10
%
1
SOC1 Clear
Threshold
U1
0
255
15
%
2
SOCF Set Threshold
U1
0
255
2
%
3
SOCF Clear
Threshold
U1
0
255
5
%
9
Hibernate I
I2
0
700
3
mA
11
Hibernate V
I2
2400
3000
2550
mV
Block A 0-11
H1
0x0
0xff
0x0
System Data
[NVM]
58
Manufacturer
Info [NVM]
0-11
Gas Gauging
[NVM/RAM]
80
IT Cfg [RAM]
41
User Rate-mA
I2
2000
9000
0
mV
43
User Rate-mW
I2
3000
14000
0
CentiW
45
Reserve Cap-mWh
I2
0
14000
0
cWattHour
0
Dsg Current
Threshold
I2
0
2000
167
mA
2
Chg Current
Threshold
I2
0
2000
133
mA
4
Quit Current
I2
0
1000
250
mA
3
Reserve Cap-mAh
I2
0
9000
0
mAh
81
82
Ra Tables
[NVM/RAM]
18
Current
Thresholds
[RAM]
State [NVM]
-
5
Op Config
H2
0x0000
0xFFFF
0x01F8
Hex
12
Design Capacity
I2
0
32767
1340
mAh
14
Design Energy
I2
0
32767
4960
mWh
18
Terminate Voltage
I2
2800
3700
3200
mV
30
Taper Current
I2
0
1000
75
mA
32
Taper Voltage
I2
0
5000
4100
mV
34
Sleep Current
I2
0
100
10
mA
88
R_a [NVM]
0 - 28
Cell0 R_a 0-14
I2
Table
Table
Table
2^–10Ω
(num)
89
R_a [RAM]
0 - 28
Cell0 R_a 0-14
I2
Table
Table
Table
2^–10Ω
(num)
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Table 7. Block Data Summary (continued)
Class
Calibration
[NVM]
Security [RAM]
SubClass
ID
SubClass
Offset
104
Data [NVM]
0
CC Delta
F4
2.98E+04
1.19E+06 567744.5
68
4
CC Offset
U2
0
65535
–1200
num (mV)
6
Board Offset
I1
–128
127
0
num (uV)
7
Int Temp Offset
I1
–128
127
0
num (°C)
8
Pack V Offset
I1
–128
127
0
num (mV)
0
CC Gain
F4
1.00E-01
4.00E+01 0.4768
4
CC Cal Temp
I2
0
32767
2982
0
Sealed to Unsealed
H4
0x0
0xffffffff
x367204
14
105
CC Cal [NVM]
112
Codes [RAM]
Name
Data
Type
Min
Max
Default
Unit
(EVSW Unit)
num
(2^–10Ω)
Num
(2^–10Ω)
0.1K
-
FUNCTIONAL DESCRIPTION
FUEL GAUGING
The bq27425 is an easy to configure fuel gauge that measures the cell voltage, temperature, and current to
determine battery state of charge (SOC). The bq27425 monitors charge and discharge activity by sensing the
voltage across a small-value resistor (5 mΩ to 20 mΩ typ.) between the SRX and VSS 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 the Design Capacity. The bq27425 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.
In addition, a FACTORY_RESTORE subcommand is provided to restore default resistance and Qmax to factory
condition.
FUEL GAUGING CONFIGURATIONS
The bq27425 features easy to configure data NVM to speed-up fuel gauging design. Users are required to
configure Design Capacity, Termination Voltage, and Operation Configuration (see The Operation
Configuration Register section for details) to achieve optimal performance. The Impedance Track™ algorithm
uses these parameters with it’s built-in parameters to achieve accurate battery fuel gauging.
Several built-in parameters are used in the Impedance Track™ algorithm to identify different modes of battery:
• Charging : Chg Current Threshold (default = DesignCapacity /13.3 ),
• Discharging: Dsg Current Threshold (default = DesignCapacity /16.7 )
• Relax: Quit Current Threshold (default = DesignCapacity /25.0 )
To achieve accurate fuel gauging, the bq27425 uses Constant Power Model for fuel gauging. This model uses
the average discharge power from the beginning of the discharge cycle until present time to compute
load-compensated capacity such as RemainingCapacity( ) and FullChargeCapacity( ) in the Impedance Track™
algorithm.
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DETAILED PIN DESCRIPTIONS
The Operation Configuration Register
Two bq27425 pins are configured via the Operation Configuration data NVM register, as indicated in Table 8.
This register is programmed/read via the methods described in Section Accessing the Data NVM.
Table 8. Operation Configuration Bit Definition
bit7
bit6
bit5
bit4
bit3
bit2
bit1
bit0
High Byte
INTSNSEN
RSVD0
BIE
BI_PU_EN
GNDSEL
RSVD0
RSVD0
RSVD1
Low Byte
RSVD1
RSVD1
SLEEP
RMFCC
RSVD1
BATLOWEN
GPIOPOL
WRTEMP
INTSNSEN = Enables temperature compensation of the integrated sense resistor. Default is 0.
BIE =
Battery Insertion Enable. If set, the battery insertion is detection via BIN pin input. If cleared, the detection relies on the
host to issue BAT_INSERT subcommand to indicate battery presence in the system. Default is 0.
BI_PU_EN = Enables internal weak pull-up on BIN pin. Default is 0 which assumes an external pull-up resistor.
GNDSEL =
The ADC ground select control. The Vss (Pin D1) is selected as ground reference when the bit is clear. Pin A1 is
selected when the bit is set. Default is 0.
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.
BATLOWEN =
If set, the BAT_LOW function for GPOUT pin is selected. If cleared, the SOC_INT function is selected for GPOUT.
Default is 0.
GPIO_POL = GPOUT pin is active-high if set or active-low if cleared. Default is 0.
WRTEMP = Enables the host to write Temperature( ) if set. If cleared, the internal temperature sensor is used for Temperature( ).
Default is 0.
RSVD0 = Reserved. Default is 0. (Set to 0 for proper operation)
RSVD1 = Reserved. Default is 1. (Set to 1 for proper operation)
GPOUT Pin
The GPOUT Pin is a multiplex pin and the polarity of the pin output can be selected via the [GPIO_POL] bit of
the Operation Configuration. The function is defined by [BATLOWEN]. If set, the Battery Low Indicator
(BAT_LOW) function for GPOUT pin is selected. If cleared, the SOC interrupt (SOC_INT) function is selected for
GPOUT.
When the BAT_LOW function is activated, the signaling on the multiplexed pin follows the status of the [SOC1]
bit in the Flags( ) register. The bq27425 has two flags accessed by the Flags( ) function that warns when the
battery’s SOC has fallen to critical levels. When StateOfCharge( ) 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
StateOfCharge( ) rises above SOC1 Set Threshold. The bq27425’s GPOUT pin automatically reflects the status
of the [SOC1] flag when OpConfig[BATLOWEN=0].
When StateOfCharge( ) falls below the second capacity threshold, SOCF Set Threshold, the [SOCF] (State of
Charge Final) flag is set, serving as a final discharge warning. Similarly, when StateOfCharge( ) rises above
SOCF Clear Threshold and the [SOCF] flag has already been set, the [SOCF] flag is cleared.
When the SOC_INT function is activated, the GPOUT pin generates 1ms pulse width under various conditions as
described in Table 9.
20
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Table 9. SOC_INT Function Definition
SOCI_Delta
Enable Condition
Pulse Width
Description
SOCI_Delta ≠ 0
1ms
During charge, when the StateOfCharge() reaches greater than or equal to (≥) the
defined SOC_INT intervals. The intervals are defined as 100% and 100% – n ×
SOCI_Delta.
During discharge, when the StateOfCharge() reaches less than ( Chg Current Threshold (default = DesignCapacity / 13.3),
then the [OTC] bit of Flags( ) is set. When Temperature() falls to OT Chg Recovery (default = 50°C), the [OTC]
of Flags() is reset.
Over-Temperature Indication: Discharge
If during discharging, Temperature( ) reaches the threshold of OT Dsg (default = 60°C) for a period of OT Dsg
Time (default = 2 seconds) , and AverageCurrent( ) ≤ -Dsg Current Threshold (default = DesignCapacity
/16.7 ) , then the [OTD] bit of Flags( ) is set. When Temperature( ) falls to OT Dsg Recovery (default = 55°C),
the [OTD] bit of Flags( ) is reset.
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DETECTING CHARGE TERMINATION
The bq27425 detects charge termination when (1) during 2 consecutive periods of Current Taper Window
(default = 40 seconds), the AverageCurrent( ) is < Taper Current (default = 100 mA), (2) during the same
periods, the accumulated change in capacity > 0.25mAh/ / Current Taper Window (default = 40 seconds), and
(3) Voltage( ) > (Charging Voltage – 100mV) where Charging Voltage = 4200mV by default. When this occurs,
the [CHG] bit of Flags( ) is cleared. Also, if the [RMFCC] bit of Operation Configuration is set, and
RemainingCapacity( ) is set equal to FullChargeCapacity( ).
Charge Inhibit
The bq27425 can indicate when battery temperature has fallen below or risen above predefined thresholds
Charge Inhibit Temp Low (default = 0˚C) or Charge Inhibit Temp High (default = 45˚C), 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 Temp Low, Charge Temp High] (default = [5˚C,40˚C]).
OPERATING MODES
The bq27425 has different operating modes: POR, INITIALIZATION, NORMAL, CONFIG UPDATE, SLEEP, and
HIBERNATE. Following Power On Reset (POR), the fuel gauge begins INITIALIZATION. In NORMAL mode, the
bq27425 is fully powered and can execute any allowable task. Configuration data in RAM and NVM can be
updated by the host using the CONFIG UPDATE mode. In SLEEP mode the fuel gauge turns off the high
frequency oscillator clock to enter a reduced-power state, periodically taking measurements and performing
calculations. In HIBERNATE mode, the fuel gauge is in a very low power state, but can be woken up by
communication or certain I/O activity.
via RESET
subcommand
(from any mode)
Power On Reset [POR]
Copy configuration ROM
defaults to RAM data.
Set Flags[ITPOR] = 1.
Exit from CONFIG UPDATE
Flags [CFGUPMODE] = 0
AND
Flags [ITPOR] = 0
INITIALIZATION
Flags
[BAT _ DET ] = 0
(via SOFT_RESET
subcommand)
Initialize algorithm and data..
Check for battery insertion.
.
(No gauging in this mode.)
CONFIG UPDATE
Host can change RAM and
NVM based data blocks.
(No gauging in this mode.)
I CC = Normal
Entry to CONFIG UPDATE
Flags [CFGUPMODE] = 1
(via SET_CFGUPDATE
subcommand)
Exit From NORMAL
Entry to NORMAL
Flags [ BAT _ DET ] = 1
Flags [BAT _ DET ] = 0
Exit From HIBERNATE
V CELL < POR threshold
NORMAL
Exit From HIBERNATE
Communication Activity
OR
bq27425 clears Control Status
[HIBERNATE ] = 0
Recommend Host also set Control
Status [HIBERNATE ] = 0
HIBERNATE
Wakeup From HIBERNATE
Communication to gauge
AND
Comm address is NOT for bq27425
Disable all subcircuits
except GPIO .
Fuel gauging and data
updated every 1s
Exit From SLEEP /FULLSLEEP
Pack Configuration
[SLEEP ] = 0
OR
| AverageCurrent ( ) | > Sleep Current
OR
Current is Detected above I WAKE
ICC = Normal
Entry to SLEEP
Pack Configuration
[SLEEP ] = 1
AND
| AverageCurrent ( ) | = Sleep Current
SLEEP
Fuel gauging and data
updated every 20 seconds
I CC = Hibernate
I CC = Sleep
Exit From
WAIT _HIBERNATE
Host must set Control Status
[HIBERNATE ] = 0
AND
VCELL > Hibernate Voltage
Exit From WAIT _ HIBERNATE
Cell relaxed
AND
| AverageCurrent () | < Hibernate
Current
OR
V CELL
Cell relaxed
AND
< Hibernate Voltage
WAIT _HIBERNATE
System Sleep
Fuel gauging and data
updated every 20 seconds
Exit From SLEEP
( Host has set Control Status
[HIBERNATE ] = 1
OR
VCELL < Hibernate Voltage
I CC = Sleep /FullSleep
System Shutdown
Figure 2. Power Mode Diagram
22
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SLUSAI6 – NOVEMBER 2011
POR and INITIALIZATION Modes
Upon Power On Reset (POR), the fuel gauge copies ROM-based configuration defaults to RAM and begins
INITIALIZATION mode where essential data is initialized and will remain in INITIALIZATION mode as
halted-CPU state when an adapter, or other power source is present to power the bq27425 (and system), yet no
battery has been detected. The occurrence of POR or a Control( ) RESET subcommand will set the Flags( )
[ITPOR] status bit to indicate that RAM has returned to ROM default data. When battery insertion is detected, a
series of initialization activities begin including an OCV measurement. In addition CONTROL_STATUS[QMAXU]
and [RESU] bits are cleared to allow fast learning of Qmax and impedance.
Some commands, issued by a system processor, can be processed while the bq27425 is halted in this mode.
The gauge will wake up to process the command, and then return to the halted state awaiting battery insertion.
The current consumption of INITIALIZATION mode is similar to NORMAL mode.
CONFIG UPDATE Mode
If the application requires different configuration data for the bq27425. The host can update both NVM and RAM
based parameters using the Control( ) SET_CFGUPDATE subcommand to enter CONFIG UPDATE mode as
indicated by the Flags( ) [CFGUPMODE] status bit. In this mode, fuel gauging is suspended while the host uses
the Extended Data Commands to modify the configuration data blocks. To resume fuel gauging, the host sends a
Control( ) SOFT_RESET subcommand to return to the INITIALIZATION mode and clear both Flags( ) [ITPOR]
and [CFGUPMODE] bits.
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 (Operation Configuration [SLEEP]) = 1) and
AverageCurrent( ) is below the programmable level Sleep Current (default = 10mA). Once entry into SLEEP
mode has been qualified, but prior to entering it, the bq27425 performs an ADC autocalibration to minimize
offset.
During SLEEP mode, the bq27425 periodically takes data measurements and updates its data set. However, a
majority of its time is spent in an idle condition.
The bq27425 exits SLEEP if any entry condition is broken, specifically when: AverageCurrent( ) rises above
Sleep Current (default = 10mA).
HIBERNATE Mode
HIBERNATE mode could be used when the system equipment needs to enter a very low-power state, and
minimal gauge power consumption is required. This mode is ideal when a system equipment is set to its own
HIBERNATE, SHUTDOWN, or OFF modes.
Before the fuel gauge can enter HIBERNATE mode, the system must set the [HIBERNATE] bit of the
CONTROL_STATUS register. The gauge waits to enter HIBERNATE mode until it has taken a valid OCV
measurement and the magnitude of the average cell current has fallen below Hibernate Current. The gauge can
also enter HIBERNATE mode if the cell voltage falls below Hibernate Voltage. The gauge will remain in
HIBERNATE mode until the system issues a direct I2C command to the gauge. I2C Communication that is not
directed to the gauge will not wake the gauge (or at least for very long).
It is the system’s responsibility to wake the bq27425 after it has gone into HIBERNATE mode and prevents a
charger from charging the battery before the [OCVTAKEN] bit is set which signals an OCV reading is taken. After
waking, the gauge can proceed with the initialization of the battery information.
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I2C INTERFACE
The bq27425 supports the standard I2C read, incremental read, quick read, one byte write, and incremental write
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 will therefore be 0xAA or 0xAB for write or read, respectively.
Host generated
S
ADDR[6:0]
0 A
bq27425 generated
CMD[7:0]
A
DATA [7:0]
A P
S
ADDR[6:0]
(a) 1-byte write
S
ADDR[6:0]
0 A
1 A
DATA [7:0]
N P
(b) quick read
CMD[7:0]
A Sr
ADDR[6:0]
1 A
DATA [7:0]
N P
(c) 1- byte read
S
ADDR[6:0]
0 A
CMD[7:0]
A Sr
ADDR[6:0]
1 A
DATA [7:0]
A ...
DATA [7:0]
N P
(d) incremental read
S
ADDR[6:0]
0 A
CMD[7:0]
A
DATA [7:0]
A
DATA [7:0]
A
...
A P
(e) incremental write
(S = Start, Sr = Repeated Start, A = Acknowledge, N = No Acknowledge, and P = Stop).
Figure 3. Supported I2C Formats
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 bq27425 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).
The following command sequences are not supported:
Attempt to write a read-only address (NACK after data sent by master):
S
ADDR[6:0]
0
A
CMD[7:0]
A
DATA[7:0]
N
P
Attempt to read an address above 0x6B (NACK command):
S
24
ADDR[6:0]
0
A
CMD[7:0]
N P
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bq27425-G1
SLUSAI6 – NOVEMBER 2011
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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, as an
example, the 66 µs waiting time required between issuing the control command and reading the status data.
Similarly, a 100 ms waiting time is required between the BlockDataChecksum( ) Extended command. For
read-write Standard Commands, such as Temperature( ), a minimum of 2 seconds is needed to observe the data
read back following the associated data write. For read-only standard commands, there is no waiting time
required; however, 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 a watchdog timer.
S
ADDR [6:0]
0 A
CMD [7:0]
A
S
ADDR [6:0]
0 A
CMD [7:0]
A Sr
DATA [7:0]
ADDR [6:0]
A
1 A
DATA [7:0]
DATA [7:0]
A P
A
66ms
DATA [7:0]
N P
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]
A
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 of approximately 75 µs will occur on all I2C traffic as the device must wake-up to process the
packet. In NORMAL mode, 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 (
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