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bq27531-G1
SLUSBE7C – MARCH 2013 – REVISED JANUARY 2016
bq27531-G1 Battery Management Unit Impedance Track™ Fuel Gauge With MaxLife™
Technology for Use With the bq2419x Charger Controller
1 Features
3
•
The Texas Instruments bq27531-G1 system-side LiIon Battery Management Unit is a microcontroller
peripheral that provides Impedance Track fuel
gauging and charging control for single-cell Li-Ion
battery packs. The device requires little system
microcontroller firmware development. Together with
the bq2419x Single-Cell Switched-Mode Charger, the
bq27531-G1 manages an embedded battery
(nonremovable) or a removable battery pack.
1
•
•
•
•
•
•
•
•
Battery Fuel Gauge and Charger Controller for 1Cell Li-Ion Applications
Resides on System Main Board
Battery Fuel Gauge Based on Patented
Impedance Track™ Technology
– Models the 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 (5 mΩ to 20 mΩ)
Battery Charger Controller With Customizable
Charge Profiles
– Configurable Charge Voltage and Current
Based on Temperature
– Optional State of Health (SoH) and MultilevelBased Charge Profiles
Host-Free Autonomous Battery Management
System
– Reduced Software Overhead Allows for Easy
Portability Across Platforms and Shorter OEM
Design Cycles
– Higher Safety and Security
Intelligent Charging—Customized and Adaptive
Charging Profiles
– Charger Control Based on SoH
– Temperature Level Charging (TLC)
Battery Charger Controller for bq2419x Single-Cell
Switched-Mode Battery Charger
– Stand-Alone Charging Solution
– SHIP Mode Capability
400-kHz I2C Interface for Connection to System
Microcontroller Port
In a 15-Pin NanoFree™ Packaging
Description
The bq27531-G1 uses the patented Impedance Track
algorithm for fuel gauging, and provides information
such as remaining battery capacity (mAh), state-ofcharge (%), run time to empty (minimum), battery
voltage (mV), temperature (°C), and state of health
(%).
Battery fuel gauging with the bq27531-G1 requires
only PACK+ (P+), PACK– (P–), and Thermistor (T)
connections to a removable battery pack or
embedded battery circuit. The CSP option is a 15-pin
package in the dimensions of 2.61 mm × 1.96 mm
with a 0.5-mm lead pitch, which is ideal for spaceconstrained applications.
Device Information(1)
PART NUMBER
PACKAGE
bq27531-G1
BODY SIZE (NOM)
DSBGA (15)
2.61 mm × 1.96 mm
(1) For all available packages, see the orderable addendum at
the end of the data sheet.
Simplified Schematic
5V USB or
AC Adapter
SW
VBUS
SYSTEM LOAD
SYS
BQ2419x
BAT
PGND
I2C
2
•
•
•
•
Applications
Smart Phones, Feature Phones, and Tablets
Digital Still and Video Cameras
Handheld Terminals
MP3 or Multimedia Players
Single Cell Li-Ion Battery Pack
Voltage
Sense
I2C
Application
Processor
Temp
Sense
P+
T
PROTECTION IC
BQ27531-G1
SOCINT
P-
FETs
Current
Sense
1
An IMPORTANT NOTICE at the end of this data sheet addresses availability, warranty, changes, use in safety-critical applications,
intellectual property matters and other important disclaimers. PRODUCTION DATA.
bq27531-G1
SLUSBE7C – MARCH 2013 – REVISED JANUARY 2016
www.ti.com
Table of Contents
1
2
3
4
5
6
7
Features ..................................................................
Applications ...........................................................
Description .............................................................
Revision History.....................................................
Device Options.......................................................
Pin Configuration and Functions .........................
Specifications.........................................................
1
1
1
2
3
3
4
7.1
7.2
7.3
7.4
7.5
7.6
7.7
7.8
7.9
7.10
4
4
4
4
5
5
5
5
5
Absolute Maximum Ratings ......................................
ESD Ratings..............................................................
Recommended Operating Conditions.......................
Thermal Information ..................................................
Electrical Characteristics: Supply Current.................
Digital Input and Output DC Characteristics .............
Power-On Reset........................................................
2.5-V LDO Regulator ................................................
Internal Clock Oscillators ..........................................
ADC (Temperature and Cell Measurement)
Characteristics ...........................................................
7.11 Integrating ADC (Coulomb Counter)
Characteristics ...........................................................
7.12 Data Flash Memory Characteristics........................
7.13 I2C-Compatible Interface Communication Timing
Characteristics ...........................................................
6
6
6
7
7.14 Typical Characteristics ............................................ 8
8
Detailed Description .............................................. 9
8.1
8.2
8.3
8.4
8.5
9
Overview ................................................................... 9
Functional Block Diagram ....................................... 10
Feature Description................................................. 11
Device Functional Modes........................................ 12
Programming........................................................... 16
Application and Implementation ........................ 21
9.1 Application Information............................................ 21
9.2 Typical Application ................................................. 21
10 Power Supply Recommendations ..................... 26
10.1 Power Supply Decoupling ..................................... 26
11 Layout................................................................... 26
11.1 Layout Guidelines ................................................. 26
11.2 Layout Example .................................................... 27
12 Device and Documentation Support ................. 28
12.1
12.2
12.3
12.4
12.5
Documentation Support ........................................
Community Resources..........................................
Trademarks ...........................................................
Electrostatic Discharge Caution ............................
Glossary ................................................................
28
28
28
28
28
13 Mechanical, Packaging, and Orderable
Information ........................................................... 28
4 Revision History
Changes from Revision B (September 2015) to Revision C
•
Page
Changed ESD Ratings ........................................................................................................................................................... 4
Changes from Revision A (June 2015) to Revision B
Page
•
Changed a Pin Functions description to correct the TRM link ............................................................................................... 3
•
Changed Figure 6 ................................................................................................................................................................ 13
•
Added Figure 7 .................................................................................................................................................................... 14
2
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SLUSBE7C – MARCH 2013 – REVISED JANUARY 2016
5 Device Options
PART NUMBER
bq27531YZFR-G1
bq27531YZFT-G1
FIRMWARE
VERSION
COMMUNICATION
FORMAT
1.02
(0x0102)
I2C
6 Pin Configuration and Functions
YZF Package
15-Pin DSBGA
(TOP VIEW)
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
A3
E
(BOTTOM VIEW)
xx
xx
Pin A1
Index Area
D
DIM
MIN
TYP
MAX
D
2580
2610
2640
E
1926
1956
1986
UNITS
m
Pin Functions
PIN
NAME
NO.
I/O (1)
DESCRIPTION
BAT
E2
I
BI/TOUT
E3
I/O
Battery insertion detection input. Power pin for pack thermistor network. Thermistor multiplexer control pin. Use with
pullup resistor >1 MΩ (1.8 MΩ typical).
BSDA
C3
I/O
Battery Charger data line for chipset communication. Push-pull output.
BSCL
B2
O
Battery Charger clock output line for chipset communication. Push-pull output.
CE
D2
I
Chip Enable. Internal LDO is disconnected from REGIN when driven low. Note: CE has an internal ESD protection
diode connected to REGIN. Recommend maintaining VCE ≤ VREGIN under all conditions.
REGIN
E1
P
Regulator input. Decouple with 0.1-μF ceramic capacitor to Vss.
SCL
A3
I
Slave I2C serial communications clock input line for communication with system (Master). Open-drain I/O. Use with
10-kΩ pullup resistor (typical).
SDA
B3
I/O
Slave I2C serial communications data line for communication with system (Master). Open-drain I/O. Use with 10-kΩ
pullup resistor (typical).
SOC_INT
A2
I/O
SOC state interrupts output. Generates a pulse as described in the bq27531-G1 Technical Reference Manual
(SLUUA96). Open-drain output.
SRN
B1
IA
Analog input pin connected to the internal coulomb counter where SRN is nearest the Vss connection. Connect to 5mΩ to 20-mΩ sense resistor.
SRP
A1
IA
Analog input pin connected to the internal coulomb counter where SRP is nearest the PACK– connection. Connect to
5-mΩ to 20-mΩ sense resistor.
TS
D3
IA
Pack thermistor voltage sense (use 103AT-type thermistor). ADC input.
VCC
D1
P
Regulator output and bq27531-G1 power. Decouple with 1-μF ceramic capacitor to Vss.
VSS
C1, C2
P
Device ground
(1)
Cell voltage measurement input. ADC input. Recommend 4.8 V maximum for conversion accuracy.
I/O = Digital input/output, IA = Analog input, P = Power connection
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7 Specifications
7.1 Absolute Maximum Ratings
over operating free-air temperature range (unless otherwise noted) (1)
MIN
MAX
–0.3
5.5
UNIT
VREGIN
Regulator input
VCE
CE input pin
–0.3
VREGIN + 0.3
V
VCC
Supply voltage
–0.3
2.75
V
VIOD
Open-drain I/O pins (SDA, SCL, SOC_INT)
–0.3
5.5
V
–0.3
5.5
–0.3
6.0
V
(2)
VBAT
BAT input pin
VI
Input voltage to all other pins
(BI/TOUT, TS, SRP, SRN, BSDA, BSCL)
–0.3
VCC + 0.3
V
TA
Operating free-air temperature
–40
85
°C
(1)
(2)
–0.3
6.0
V
(2)
Stresses beyond those listed under Absolute Maximum Ratings may cause permanent damage to the device. These are stress ratings
only, which do not imply functional operation of the device at these or any other conditions beyond those indicated under Recommended
Operating Conditions. Exposure to absolute-maximum-rated conditions for extended periods may affect device reliability.
Condition not to exceed 100 hours at 25°C lifetime.
7.2 ESD Ratings
VALUE
Electrostatic
discharge
V(ESD)
(1)
(2)
Human body model (HBM), per ANSI/ESDA/JEDEC JS-001, BAT pin (1)
±1500
Human-body model (HBM), per ANSI/ESDA/JEDEC JS-001), All other pins (1)
±2000
Charged device model (CDM), per JEDEC specification JESD22-C101 (2)
±250
UNIT
V
JEDEC document JEP155 states that 500-V HBM allows safe manufacturing with a standard ESD control process.
JEDEC document JEP157 states that 250-V CDM allows safe manufacturing with a standard ESD control process.
7.3 Recommended Operating Conditions
TA = –40°C to 85°C, VREGIN = VBAT = 3.6 V (unless otherwise noted)
MIN
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
tPUCD
Power-up communication delay
No flash writes
Nominal capacitor values specified.
Recommend a 5% ceramic X5R type
capacitor located close to the device.
NOM
MAX
2.8
4.5
2.45
2.8
UNIT
V
0.1
μF
1
μF
250
ms
0.47
7.4 Thermal Information
bq27531-G1
THERMAL METRIC (1)
YZF [DSBGA]
UNIT
15 PINS
RθJA
Junction-to-ambient thermal resistance
70
°C/W
RθJC(top)
Junction-to-case(top) thermal resistance
17
°C/W
RθJB
Junction-to-board thermal resistance
20
°C/W
ψJT
Junction-to-top characterization parameter
1
°C/W
ψJB
Junction-to-board characterization parameter
18
°C/W
RθJC(bot)
Junction-to-case(bottom) thermal resistance
N/A
°C/W
(1)
4
For more information about traditional and new thermal metrics, see the Semiconductor and IC Package Thermal Metrics application
report, SPRA953.
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SLUSBE7C – MARCH 2013 – REVISED JANUARY 2016
7.5 Electrical Characteristics: Supply Current
TA = 25°C and VREGIN = VBAT = 3.6 V (unless otherwise noted)
PARAMETER
TEST CONDITIONS
MIN
TYP
MAX
UNIT
ICC (1)
NORMAL operating mode current
Fuel gauge in NORMAL mode
ILOAD > Sleep current
118
μA
ISLP+ (1)
SLEEP+ operating mode current
Fuel gauge in SLEEP+ mode
ILOAD < Sleep current
62
μA
ISLP (1)
Low-power storage mode current
Fuel gauge in SLEEP mode
ILOAD < Sleep current
23
μA
IHIB (1)
HIBERNATE operating mode current
Fuel gauge in HIBERNATE mode
ILOAD < Hibernate current
8
μA
(1)
Specified by design. Not production tested.
7.6 Digital Input and Output DC 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
VOL
Output voltage, low (SCL, SDA,
SOC_INT, BSDA, BSCL)
IOL = 3 mA
VOH(PP)
Output voltage, high (BSDA, BSCL)
IOH = –1 mA
VCC – 0.5
VOH(OD)
Output voltage, high (SDA, SCL,
SOC_INT)
External pullup resistor connected to
VCC
VCC – 0.5
Input voltage, low (SDA, SCL)
VIL
Input voltage, low (BI/TOUT)
Input voltage, high (SDA, SCL)
VIH
Input voltage, high (BI/TOUT)
VIL(CE)
Input voltage, low (CE)
VIH(CE)
Input voltage, high (CE)
Ilkg
BAT INSERT CHECK mode active
(1)
(1)
TYP
MAX
0.4
VREGIN = 2.8 V to 4.5 V
V
V
–0.3
0.6
–0.3
0.6
1.2
BAT INSERT CHECK mode active
UNIT
1.2
VCC + 0.3
0.8
2.65
Input leakage current (I/O pins)
0.3
V
V
V
μA
Specified by design. Not production tested.
7.7 Power-On Reset
TA = –40°C to 85°C, typical values at TA = 25°C and VREGIN = 3.6 V (unless otherwise noted)
PARAMETER
VIT+
Positive-going battery voltage input at
VCC
VHYS
Power-on reset hysteresis
TEST CONDITIONS
MIN
TYP
MAX
UNIT
2.05
2.15
2.20
V
115
mV
7.8 2.5-V LDO Regulator
TA = –40°C to 85°C, CLDO25 = 1 μF, VREGIN = 3.6 V (unless otherwise noted)
PARAMETER
VREG25
(1)
Regulator output voltage (VCC)
TEST CONDITION
MIN
TYP
MAX
2.8 V ≤ VREGIN ≤ 4.5 V, IOUT ≤ 16 mA (1)
2.3
2.5
2.6
2.45 V ≤ VREGIN < 2.8 V (low battery),
IOUT ≤ 3mA
2.3
UNIT
V
LDO output current, IOUT, is the total load current. LDO regulator must be used to power internal fuel gauge only.
7.9 Internal Clock Oscillators
TA = –40°C to 85°C, 2.4 V < VCC < 2.6 V; typical values at TA = 25°C and VCC = 2.5 V (unless otherwise noted)
PARAMETER
TEST CONDITIONS
MIN
TYP
MAX
UNIT
fOSC
High-frequency oscillator
8.389
MHz
fLOSC
Low-frequency oscillator
32.768
kHz
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7.10 ADC (Temperature and Cell Measurement) Characteristics
TA = –40°C to 85°C, 2.4 V < VCC < 2.6 V; typical values at TA = 25°C and VCC = 2.5 V (unless otherwise noted)
PARAMETER
TEST CONDITIONS
MIN
TYP
MAX
VADC1
Input voltage (TS)
VSS –
0.125
2
VADC2
Input voltage (BAT)
VSS –
0.125
5
VIN(ADC)
Input voltage
GTEMP
Internal temperature sensor voltage
gain
tADC_CONV
Conversion time
0.05
Resolution
VOS(ADC)
(1)
Effective input resistance (TS)
ZADC2
(1)
Effective input resistance (BAT)
(1)
Ilkg(ADC)
(1)
V
ms
15
bits
mV
8
MΩ
8
bq27531-G1 measuring cell voltage
V
125
1
bq27531-G1 not measuring cell voltage
V
mV/°C
14
Input offset
ZADC1
1
–2
UNIT
MΩ
100
kΩ
Input leakage current
0.3
μA
Specified by design. Not tested in production.
7.11 Integrating ADC (Coulomb Counter) Characteristics
TA = –40°C to 85°C, 2.4 V < VCC < 2.6 V; typical values at TA = 25°C and VCC = 2.5 V (unless otherwise noted)
PARAMETER
TEST CONDITIONS
VSR
Input voltage,
V(SRP) and V(SRN)
VSR = V(SRP) – V(SRN)
tSR_CONV
Conversion time
Single conversion
Resolution
VOS(SR)
Input offset
INL
Integral nonlinearity error
ZIN(SR)
(1)
(1)
TYP
–0.125
MAX
UNIT
0.125
V
1
s
14
15
bits
±0.034%
FSR
μV
10
±0.007%
Effective input resistance
Ilkg(SR) (1)
MIN
2.5
MΩ
Input leakage current
0.3
μA
Specified by design. Not tested in production.
7.12 Data Flash Memory Characteristics
TA = –40°C to 85°C, 2.4 V < VCC < 2.6 V; typical values at TA = 25°C and VCC = 2.5 V (unless otherwise noted)
PARAMETER
tDR
(1)
TEST CONDITIONS
Data retention
Flash-programming write
cycles (1)
tWORDPROG
(1)
ICCPROG
(1)
tDFERASE
tIFERASE
(1)
tPGERASE
(1)
6
(1)
(1)
MIN
TYP
MAX
UNIT
10
Years
20000
Cycles
Word programming time
Flash-write supply current
5
2
ms
10
mA
Data flash master erase time
200
ms
Instruction flash master erase
time
200
ms
20
ms
Flash page erase time
Specified by design. Not production tested.
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7.13 I2C-Compatible Interface Communication Timing Characteristics
TA = –40°C to 85°C, 2.4 V < VCC < 2.6 V; typical values at TA = 25°C and VCC = 2.5 V (unless otherwise noted)
PARAMETER
MIN
NOM
MAX
UNIT
tr
SCL/SDA rise time
300
ns
tf
SCL/SDA fall time
300
ns
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
tsu(STOP)
Setup time for stop
t(BUF)
Bus free time between stop and start
fSCL
(1)
Clock frequency
0
ns
600
ns
66
μs
(1)
400
kHz
If the clock frequency (fSCL) is > 100 kHz, use 1-byte write commands for proper operation. All other transactions types are supported at
400 kHz. (See I2C Interface and I2C Command Waiting Time).
Figure 1. I2C-Compatible Interface Timing Diagrams
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7.14 Typical Characteristics
8.8
VREGIN = 2.7 V
VREGIN = 4.5 V
2.6
fOSC - High Frequency Oscillator (MHz)
VREG25 - Regulator Output Voltage (V)
2.65
2.55
2.5
2.45
2.4
2.35
8.7
8.6
8.5
8.4
8.3
8.2
8.1
8
-40
Temperature (qC)
-20
0
20
40
Temperature (qC)
D001
34
5
33.5
4
33
32.5
32
31.5
31
30.5
30
-40
-20
0
20
40
Temperature (qC)
60
80
100
8
100
D002
3
2
1
0
-1
-2
-3
-4
-5
-30
-20
D003
Figure 4. Low-Frequency Oscillator Frequency vs
Temperature
80
Figure 3. High-Frequency Oscillator Frequency vs
Temperature
Reported Temperature Error (qC)
fLOSC - Low Frequency Oscillator (kHz)
Figure 2. Regulator Output Voltage vs Temperature
60
-10
0
10
20
30
Temperature (qC)
40
50
60
D004
Figure 5. Reported Internal Temperature Measurement vs
Temperature
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8 Detailed Description
8.1 Overview
The fuel gauge 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
remaining capacity and state-of-charge (SOC) as well as SOC interrupt signal to the host.
The fuel gauge can control a bq2419x Charger IC without the intervention from an application system processor.
Using the bq27531-G1 and bq2419x chipset, batteries can be charged with the typical constant-current,
constant-voltage (CCCV) profile or charged using a Multi-Level Charging (MLC) algorithm.
NOTE
Formatting conventions used in this document:
Commands: italics with parentheses and no breaking spaces, for example, Control()
Data flash: italics, bold, and breaking spaces, for example, Design Capacity
Register bits and flags: brackets and italics, for example, [TDA]
Data flash bits: brackets, italics and bold, for example, [LED1]
Modes and states: ALL CAPITALS, for example, UNSEALED mode
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8.2 Functional Block Diagram
REGIN
LDO
POR
2.5 V
VCC
HFO
BAT
CC
HFO
SRN
LFO
HFO/128
4R
HFO/128
SRP
MUX
ADC
R
Wake
Comparator
TS
Internal
Temp
Sensor
BI/TOUT
HFO/4
SDA
SOCINT
22
I2C Slave
Engine
Instruction
ROM
22
CPU
VSS
SCL
I/O
Controller
Instruction
FLASH
BSDA
8
Wake
and
Watchdog
Timer
10
GP Timer
and
PWM
8
I2C Master
Engine
BSCL
Data
SRAM
Data
FLASH
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8.3 Feature Description
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 control and status registers, as well as
its data flash locations. Commands are sent from system to gauge using the I2C serial communications engine,
and can be executed during application development, pack manufacture, or end-equipment operation.
Cell information is stored in nonvolatile 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 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 key to the high-accuracy gas gauging prediction is the TI proprietary Impedance Track algorithm. This
algorithm uses cell measurements, characteristics, and properties to create SOC predictions that can achieve
less than 1% error across a wide variety of operating conditions and over the lifetime of the battery.
The fuel gauge measures the charging and discharging of the battery by monitoring the voltage across a smallvalue series sense resistor (5 to 20 mΩ, typical) located between the system VSS and the battery PACK–
terminal. When a cell is attached to the fuel gauge, cell impedance is computed, based on cell current, cell opencircuit voltage (OCV), and cell voltage under loading conditions.
The external temperature sensing is optimized with the use of a high-accuracy negative temperature coefficient
(NTC) thermistor with R25 = 10.0 kΩ ±1%, B25/85 = 3435 K ±1% (such as Semitec NTC 103AT). The fuel gauge
can also be configured to use its internal temperature sensor. When an external thermistor is used, a 18.2-kΩ
pullup resistor between the BI/TOUT and TS pins is also required. The fuel gauge uses temperature to monitor
the battery-pack environment, which is used for fuel gauging and cell protection functionality.
To minimize power consumption, the fuel gauge has different power modes: NORMAL, SLEEP, SLEEP+,
HIBERNATE, and BAT INSERT CHECK. The fuel gauge passes automatically between these modes, depending
upon the occurrence of specific events, though a system processor can initiate some of these modes directly.
For complete operational details, see the bq27531-G1 Technical Reference Manual (SLUUA96).
8.3.1 Functional Description
The fuel gauge measures the cell voltage, temperature, and current to determine battery SOC. The fuel gauge
monitors the charging and discharging of the battery by sensing the voltage across a small-value resistor (5 mΩ
to 20 mΩ, typical) between the SRP and SRN pins and in series with the cell. By integrating charge passing
through the battery, the battery 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 SOC and chemical capacity (Qmax). The
initial Qmax values are taken from a cell manufacturer's data sheet multiplied by the number of parallel cells. It is
also used for the value in Design Capacity. The fuel gauge 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 fuel gauge has two flags accessed by the Flags() function that warn when the battery SOC has fallen to
critical levels. When RemainingCapacity() falls below the first capacity threshold as 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.
When the voltage is discharged to Terminate Voltage, the SOC will be set to 0.
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8.4 Device Functional Modes
8.4.1 Power Modes
The fuel gauge has different power modes:
• BAT INSERT CHECK: The BAT INSERT CHECK mode is a powered-up, but low-power halted, state where
the fuel gauge resides when no battery is inserted into the system.
• NORMAL: In NORMAL mode, the fuel gauge is fully powered and can execute any allowable task.
• SLEEP: In SLEEP mode, the fuel gauge turns off the high-frequency oscillator and exists in a reduced- power
state, periodically taking measurements and performing calculations.
• SLEEP+: In SLEEP+ mode, both low-frequency and high-frequency oscillators are active. Although the
SLEEP+ mode has higher current consumption than the SLEEP mode, it is also a reduced power mode.
• HIBERNATE: In HIBERNATE mode, the fuel gauge is in a low power state, but can be woken up by
communication or certain I/O activity.
The relationship between these modes is shown in Figure 6 and Figure 7.
8.4.1.1 BAT INSERT CHECK Mode
This mode is a halted-CPU state that occurs when an adapter, or other power source, is present to power the
fuel gauge (and system), yet no battery has been detected. When battery insertion is detected, a series of
initialization activities begin, which include: OCV measurement, setting the Flags() [BAT_DET] bit, and selecting
the appropriate battery profiles.
Some commands, issued by a system processor, can be processed while the fuel gauge is halted in this mode.
The gauge wakes up to process the command, then returns to the halted state awaiting battery insertion.
8.4.1.2 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.
8.4.1.3 SLEEP Mode
SLEEP mode is entered automatically if the feature is enabled (Op Config [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 fuel gauge performs a coulomb counter autocalibration to minimize offset.
During SLEEP mode, the fuel gauge periodically takes data measurements and updates its data set. However, a
majority of its time is spent in an idle condition.
The fuel gauge exits SLEEP mode if any entry condition is broken, specifically when:
• AverageCurrent() rises above Sleep Current, or
• A current in excess of IWAKE through RSENSE is detected.
In the event that a battery is removed from the system while a charger is present (and powering the gauge),
Impedance Track updates are not necessary. Hence, the fuel gauge enters a state that checks for battery
insertion and does not continue executing the Impedance Track algorithm.
12
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Device Functional Modes (continued)
Exit From HIBERNATE
Battery Removed
POR
BAT INSERT CHECK
Exit From HIBERNATE
Communication Activity
AND Comm address is for bq27531
bq27531 clears CONTROL_STATUS
[HIBERNATE] = 0
Recommend Host also set
CONTROL_STATUS
[HEBERNATE] = 0
Check for battery insertion
from HALT state.
No gauging
Entry To NORMAL
Flags [BAT_DET] = 1
Exit From NORMAL
Flags [BAT_DET] = 0
NORMAL
Entry To SLEEP+
Operation Configuration [SLEEP] = 1
AND
CONTROL_STAUS [SNOOZE] = 1]
AND
Ι AverageCurrent ( ) Ι < Sleep Current
Flags [BAT_DET] = 0
Fuel gauging and data
updated every second
Exit From SLEEP
Flags [BAT_DET] = 0
Exit From SLEEP
Ι AverageCurrent ( ) Ι > Sleep Current
OR
Current is detected above Ι WAKE
Exit From SLEEP+
Any communication to the gauge
OR
Ι AverageCurrent ( ) Ι > Sleep Current
OR
Current is detected above Ι WAKE
SLEEP+
Entry To SLEEP+
Operation Configuration [SLEEP] = 1
Fuel gauging and data
updated every 20 seconds.
Both LFO and HFO are ON.
AND
Ι AverageCurrent ( ) Ι < Sleep Current
AND
CONTROL_STAUS [SNOOZE] = 0
Entry to SLEEP+
CONTROL_STATUS [SNOOZE] = 1
Entry to SLEEP
CONTROL_STATUS [SNOOZE] = 0
SLEEP
Fuel gauging and data
updated every 20 seconds.
(LFO ON and HFO OFF)
Exit From WAIT_HIBERNATE
Host must set CONTROL_STATUS
[HIBERNATE] = 0
AND
VCELL < Hibernate Voltage
To WAIT_HIBERNATE
System Sleep
Exit From SLEEP
Host has set CONTROL_STATUS
[HIBERNATE] = 1
OR
VCELL < Hibernate Voltage
Figure 6. Power Mode Diagram—System Sleep
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Device Functional Modes (continued)
POR
Exit From HIBERNATE
Battery Removed
Exit From HIBERNATE
Communication Activity
AND Comm address is for bq27531
bq27531 clears CONTROL_STATUS
[HIBERNATE] = 0
Recommend Host also set
CONTROL_STATUS
[HEBERNATE] = 0
Exit From SLEEP
Flags [BAT_DET] = 0
BAT INSERT CHECK
Check for battery insertion
from HALT state.
No gauging
Entry To NORMAL
Flags [BAT_DET] = 1
Flags [BAT_DET] = 0
Exit From NORMAL
Flags [BAT_DET] = 0
NORMAL
Fuel gauging and data
updated every second.
HIBERNATE
Disable all bq27531
subcircuits.
Wakeup From HIBERNATE
Communication Activity
AND
Comm address is not for
bq27531
Exit From WAIT_HIBERNATE
Host must set CONTROL_STATUS
[HIBERNATE] = 0
AND
VCELL < Hibernate Voltage
To SLEEP
WAIT_HIBERNATE
Exit From WAIT_HIBERNATE
Cell relaxed
AND
Ι AverageCurrent () Ι < Hibernate
Current
OR
Cell relaxed
AND
VCELL < Hibernate Voltage
Fuel gauging and data
updated every 20 seconds.
Exit From SLEEP
Host has set CONTROL_STATUS
[HIBERNATE] = 1
OR
VCELL < Hibernate Voltage
System Shutdown
Figure 7. Power Mode Diagram—System Shutdown
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Device Functional Modes (continued)
8.4.2 SLEEP+ Mode
Compared to the SLEEP mode, SLEEP+ mode has the high-frequency oscillator in operation. The
communication delay could be eliminated. The SLEEP+ mode is entered automatically if the feature is enabled
(CONTROL_STATUS [SNOOZE] = 1) and AverageCurrent() is below the programmable level Sleep Current.
During SLEEP+ mode, the fuel gauge periodically takes data measurements and updates its data set. However,
a majority of its time is spent in an idle condition.
The fuel gauge exits SLEEP+ mode if any entry condition is broken, specifically when:
• Any communication activity with the gauge, or
• AverageCurrent() rises above Sleep Current , or
• A current in excess of IWAKE through RSENSE is detected.
8.4.3 HIBERNATE Mode
HIBERNATE mode should be used when the system equipment needs to enter a low-power state, and minimal
gauge power consumption is required. This mode is ideal when system equipment is set to its own HIBERNATE,
SHUTDOWN, or OFF mode.
Before the fuel gauge can enter HIBERNATE mode, the system must set the CONTROL_STATUS
[HIBERNATE] bit. 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 and a valid OCV measurement has been
taken. The gauge remains in HIBERNATE mode until the system issues a direct I 2 C command to the gauge or
a POR occurs. Any I 2 C communication that is not directed to the gauge does not wake the gauge.
It is the responsibility of the system to wake the fuel gauge after it has gone into HIBERNATE mode. After
waking, the gauge can proceed with the initialization of the battery information (OCV, profile selection, and so
forth).
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8.5 Programming
8.5.1 Data Commands
8.5.1.1 Standard Data Commands
The bq27531-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. 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 details are
found in the bq27531-G1 Technical Reference Manual (SLUUA96).
Table 1. Standard Commands
COMMAND CODE
UNIT
SEALED
ACCESS
UNSEALED
ACCESS
Control()
0x00 and 0x01
NA
R/W
R/W
AtRate()
0x02 and 0x03
mA
R/W
R/W
AtRateTimeToEmpty()
0x04 and 0x05
Minutes
R
R/W
Temperature()
0x06 and 0x07
0.1 K
R/W
R/W
NAME
Voltage()
0x08 and 0x09
mV
R
R/W
Flags()
0x0A and 0x0B
Hex
R
R/W
NominalAvailableCapacity()
0x0C and 0x0D
mAh
R
R/W
FullAvailableCapacity()
0x0E and 0x0F
mAh
R
R/W
RemainingCapacity()
0x10 and 0x11
mAh
R
R/W
FullChargeCapacity()
0x12 and 0x13
mAh
R
R/W
AverageCurrent()
0x14 and 0x15
mA
R
R/W
TimeToEmpty()
0x16 and 0x17
Minutes
R
R/W
RemainingCapacityUnfiltered()
0x18 and 0x19
mAh
R
R/W
StandbyCurrent()
0x1A and 0x1B
mA
R
R/W
RemainingCapacityFiltered()
0x1C and 0x1D
mAh
R
R/W
ProgChargingCurrent()
0x1E and 0x1F
mA
R (1)
R (1)
(1)
R (1)
ProgChargingVoltage()
0x20 and 0x21
mV
FullChargeCapacityUnfiltered()
0x22 and 0x23
mAh
R
R/W
AveragePower()
0x24 and 0x25
mW
R
R/W
FullChargeCapacityFiltered()
0x26 and 0x27
mAh
R
R/W
StateOfHealth()
0x28 and 0x29
%/num
R
R/W
CycleCount()
0x2A and 0x2B
Counters
R
R/W
StateOfCharge()
0x2C and 0x2D
%
R
R/W
TrueSOC()
0x2E and 0x2F
%
R
R/W
InstantaneousCurrentReading()
0x30 and 0x31
mA
R
R/W
InternalTemperature()
0x32 and 0x33
0.1 K
R
R/W
ChargingLevel()
0x34 and 0x35
Num
R
R
LevelTaperCurrent()
0x6E and 0x6F
mA
R
R
CalcChargingCurrent()
0x70 and 0x71
mA
R
R
CalcChargingVoltage()
0x72 and 0x73
V
R
R
(1)
16
R
Only writeable when Charger Options [BYPASS] is set.
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8.5.1.1.1
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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
bq27531-G1 during normal operation and additional features when the device is in different access modes, as
described in Table 2. Additional details are found in the bq27531-G1 Technical Reference Manual (SLUUA96).
Table 2. Control() Subcommands
CNTL
DATA
SEALED
ACCESS
CONTROL_STATUS
0x0000
Yes
Reports the status of hibernate, IT, and so forth
DEVICE_TYPE
0x0001
Yes
Reports the device type (for example, 0x0531 for bq27531)
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
Yes
Returns previous MAC 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 the internal CC offset
CC_OFFSET_SAVE
0x000b
No
Forces the device to store the internal CC offset
OCV_CMD
0x000c
Yes
Request the gauge to take a OCV measurement
BAT_INSERT
0x000d
Yes
Forces the BAT_DET bit set when the [BIE] bit is 0
BAT_REMOVE
0x000e
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_SLEEP+
0x0013
Yes
Forces CONTROL_STATUS [SNOOZE] to 1
CLEAR_SLEEP+
0x0014
Yes
Forces CONTROL_STATUS [SNOOZE] to 0
OTG_ENABLE
0x0015
Yes
Commands the bq2419x into USB On The Go mode
OTG_DISABLE
0x0016
Yes
Disables OTG mode at the bq2419x
DIV_CUR_ENABLE
0x0017
Yes
Makes the programmed charge current to be half of what is calculated
by the gauge charging algorithm.
CHG_ENABLE
0x001A
Yes
Enable charger. Charge will continue as dictated by gauge charging
algorithm.
CHG_DISABLE
0x001B
Yes
Disable charger (Set CE bit of bq2419x)
GG_CHGRCTL_ENABLE
0x001C
Yes
Enables the gas gauge to control the charger while continuously
resetting the charger watchdog
GG_CHGRCTL_DISABLE
0x001D
Yes
The gas gauge stops resetting the charger watchdog
DIV_CUR_DISABLE
0x001E
Yes
Makes the programmed charge current to be same as what is
calculated by the gauge charging algorithm.
DF_VERSION
0x001F
Yes
Returns the data flash version
SEALED
0x0020
No
Places device in SEALED access mode
IT_ENABLE
0x0021
No
Enables the Impedance Track algorithm
RESET
0x0041
No
Forces a full reset of the bq27531-G1
SHIPMODE_ENABLE
0x0050
Yes
Commands the bq2419x to turn off BATFET after a delay time
programmed in data flash so that system load does not draw power
from battery
SHIPMODE_DISABLE
0x0051
Yes
Commands the bq2419x to disregard turning off BATFET before delay
time or turns on commands BATFET to turn on if an VBUS had power
during the SHIPMODE enabling process
CNTL FUNCTION
DESCRIPTION
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8.5.1.2 Charger Data Commands
The charger registers are mapped to a series of single byte Charger Data Commands to enable system reading
and writing of battery charger registers. During charger power up, the registers are initialized to Charger Reset
State. The fuel gauge can change the values of these registers during the System Reset State.
Each of the bits in the Charger Data Commands can be read/write. It is important to note that System Access
can be different from the read/write access as defined in bq2419x charger hardware. The fuel gauge may block
write access to the charger hardware when the bit function is controlled by the fuel gauge exclusively. For
example, the [VREGx] bits of Chrgr_Voltage_Reg4 are controlled by the fuel gauge and cannot be modified by
system.
The bq27531 reads the corresponding registers of System_Stat_Reg8() and Fault_Reg9() every second to mirror
the charger status. Other registers in the bq2419x are read when registers are modified by the bq27531.
Table 3. Charger Data Commands
COMMAND CODE
bq2419x
CHARGER
MEMORY
LOCATION
SEALED
ACCESS
UNSEALED
ACCESS
CHGRSTAT
0x74
NA
R
R
Every second
Chrgr_InCtrl_Reg0()
CHGR0
0x75
0x00
R/W
R/W
Data Change
Chrgr_POR_Config_Reg1()
CHGR1
0x76
0x01
R/W
R/W
Data Change
Chrgr_Current_Reg2()
CHGR2
0x77
0x02
R/W
R/W
Data Change
Chrgr_PreTerm_Reg3()
CHGR3
0x78
0x03
R/W
R/W
Data Change
Chrgr_Voltage_Reg4()
CHGR4
0x79
0x04
R/W
R/W
Data Change
Chrgr_TermTimer_Reg5()
CHGR5
0x7a
0x05
R/W
R/W
Data Change
Chrgr_IRThermal_Reg6()
CHGR6
0x7b
0x06
R/W
R/W
Data Change
Chrgr_OpCtrl_Reg7()
CHGR7
0x7c
0x07
R/W
R/W
Data Change
Chrgr_Status_Reg8()
CHGR8
0x7d
0x08
R/W
R/W
Every Second
Chrgr_Fault_Reg9()
CHGR9
0x7e
0x09
R/W
R/W
Every Second
Chrgr_Rev_RegA()
CHGRA
0x7f
0x0a
R/W
R/W
Data Change
NAME
ChargerStatus()
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8.5.2 Communications
8.5.2.1 I2C Interface
The fuel gauge 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 first 8 bits of the I2C protocol are, therefore, 0xAA or 0xAB for write or read, respectively.
Host generated
S
ADDR[6:0]
0 A
Gauge generated
CMD [7:0]
A
DATA [7:0]
A P
S
ADDR[6:0]
1 A
(a) 1-byte write
S
ADDR[6:0]
0 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 8. 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 bq27531-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).
The following command sequences are not supported:
Attempt to write a read-only address (NACK after data sent by master):
Figure 9. Attempt to Write a Read-Only Address
Attempt to read an address above 0x6B (NACK command):
Figure 10. Attempt to Read an Address Above 0x6B
8.5.2.2 I2C Time-Out
The I2C engine releases both SDA and SCL if the I2C bus is held low for 2 seconds. If the bq27531-G1 is holding
the lines, releasing them frees them for 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.
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8.5.2.3 I2C Command Waiting Time
To ensure proper operation at 400 kHz, a t(BUF) ≥ 66 μs bus-free waiting time must be inserted between all
packets addressed to the bq27531-G1 . In addition, if the SCL clock frequency (fSCL) is > 100 kHz, use individual
1-byte write commands for proper data flow control. The following diagram shows the standard waiting time
required between issuing the control subcommand the reading the status result. For read-write standard
command, 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 must not issue any standard command 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]
A P
66ms
S
ADDR [6:0]
0 A
CMD [7:0]
A
DATA [7:0]
A P
66ms
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
66ms
N P
66ms
Waiting time inserted between two 1-byte write packets for a subcommand and reading results
(required for 100 kHz < fSCL £ 400 kHz)
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]
A
66ms
DATA [7:0]
Waiting time inserted between incremental 2-byte write packet for a subcommand and reading results
(acceptable for fSCL £ 100 kHz)
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
DATA [7:0]
A
66ms
Waiting time inserted after incremental read
Figure 11. I2C Command Waiting Time
8.5.2.4 I2C Clock Stretching
A clock stretch can occur during all modes of fuel gauge operation. In SLEEP and HIBERNATE modes, a short
clock stretch occurs on all I2C traffic as the device must wake up to process the packet. In the other modes
( BAT INSERT CHECK , NORMAL, SLEEP+ ) clock stretching only occurs for packets addressed for the fuel
gauge. The majority of clock stretch periods are small as the I2C interface performs normal data flow control.
However, less frequent yet more significant clock stretch periods may occur as blocks of Data Flash are updated.
The following table summarizes the approximate clock stretch duration for various fuel gauge operating
conditions.
Table 4. I2C Clock Stretching
GAUGING
MODE
APPROXIMATE
DURATION
OPERATING CONDITION/COMMENT
SLEEP
HIBERNATE
Clock stretch occurs at the beginning of all traffic as the device wakes up.
≤ 4 ms
BAT INSERT
CHECK
NORMAL
SLEEP+
Clock stretch occurs within the packet for flow control (after a start bit, ACK or first data bit).
≤ 4 ms
Normal Ra table Data Flash updates.
24 ms
20
Data Flash block writes.
72 ms
Restored Data Flash block write after loss of power.
116 ms
End of discharge Ra table Data Flash update.
144 ms
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9 Application and Implementation
NOTE
Information in the following applications sections is not part of the TI component
specification, and TI does not warrant its accuracy or completeness. TI’s customers are
responsible for determining suitability of components for their purposes. Customers should
validate and test their design implementation to confirm system functionality.
9.1 Application Information
The fuel gauge can control a bq2419x Charger IC without the intervention from an application system processor.
Using the bq27531-G1 and bq2419x chipset, batteries can be charged with the typical constant-current,
constant-voltage (CCCV) profile or charged using a Multi-Level Charging (MLC) algorithm.
9.2 Typical Application
1
2
Vin
GND
C5
1.0uF
J1
1
2
3
4
PSEL
PG
STAT
5
6
7
8
9
10
11
12
BSCL
BSDA
OTG
CE
R7
REGN
80.6k
24
23
22
21
C2
10uF
J5
2
1
L1
2.2uH
C7
47nF
1
SW
System Output
GND
SYS
2
C8
10uF
C9
10uF
C10
1uF
C11
0.1uF
TP13
SYS
BAT+
C13
10uF
R11
100k
169
C1
10uF
REGN
4.7uF C6
20
19
18
17
16
15
14
13
25
R2
U1
BQ2419xRGE
VBUS VBUS
PSEL
PMID
PG
REGN
STAT
BTST
SCL
SW
SDA
SW
PGND
INT
PGND
OTG
CE
SYS
ILIM
SYS
TS 1
BAT
TS2
BAT
PwPd
C14
1uF
VCC
R17
10.0k
SDA
SCL
VSS
J10
R18
10.0k
SYS
SDA
4
3
2
1
SCL
CE
OTG
R19
J P3
1MΩ
R20
SYS
SYS
R9
2.21k
R8
2.21k
J P4
D1
1MΩ
Green
D2
Green
PG
STAT
VCC
R23
10.0k
SOC_INT
SOC_INT
2
VSS
1
J13
SYS
C15
0.1uF
VCC
R21
1.80M
C17
1.0uF
SDA
SCL
C18
0.033uF
R22
18.2k
U2
BQ27531-G1YFF
E1 REGIN
BAT
D1
VCC
CE
B3 SDA
SOC_INT
A3 SCL
E3 BI/TOUT BSCL
BSDA
D3 TS
SRN
C2 VSS
SRP
C1 VSS
E2
D2
A2
B2
C3
B1
A1
BAT+
SYS
SOC_INT
BSCL
BSDA
TS_GAUGE
0.1uF
C19
TS_GAUGE
Vin Max: 4.4V
Current max: 4A
C16
0.1uF
PACK+
3
T
2
PACK1
J12
0.01
R24
R25
1.00k
C20
0.1uF
Only needed when the
Gauge is monitoring the
battery NTC.
Figure 12. Typical Application Schematic
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Typical Application (continued)
9.2.1 Design Requirements
Several key parameters must be updated to align with a given application's battery characteristics. For highest
accuracy gauging, it is important to follow-up this initial configuration with a learning cycle to optimize resistance
and maximum chemical capacity (Qmax) values prior to sealing and shipping systems to the field. Successful
and accurate configuration of the fuel gauge for a target application can be used as the basis for creating a
"golden" gas gauge (.fs) file that can be written to all gauges, assuming identical pack design and Li-ion cell
origin (chemistry, lot, and so on). Calibration data is included as part of this golden GG file to cut down on
system production time. If going this route, TI recommends averaging the voltage and current measurement
calibration data from a large sample size and use these in the golden file. Table 5 lists the items that must be
configured to achieve reliable protection and accurate gauging with minimal initial configuration.
Table 5. Key Data Flash Parameters for Configuration
NAME
DEFAULT
UNIT
RECOMMENDED SETTING
Design Capacity
2425
mAh
Set based on the nominal pack capacity as interpreted from cell manufacturer's
datasheet. If multiple parallel cells are used, must be set to N × Cell Capacity.
Reserve Capacity-mAh
0
mAh
Set to desired runtime remaining (in seconds/3600) × typical applied load
between reporting 0% SOC and reaching Terminate Voltage, if needed.
Cycle Count Threshold
900
mAh
Set to 90% of configured Design Capacity.
Must be configured using TI-supplied Battery Management Studio software.
Default open-circuit voltage and resistance tables are also updated in
conjunction with this step. Do not attempt to manually update reported Device
Chemistry as this does not change all chemistry information. Always update
chemistry using the appropriate evaluation software tool.
Chem ID
1202
hex
Load Mode
0
—
Set to applicable load model, 0 for constant current or 1 for constant power.
Load Select
1
—
Set to load profile which most closely matches typical system load.
Qmax Cell 0
2425
mAh
Set to initial configured value for Design Capacity. The gauge will update this
parameter automatically after the optimization cycle and for every regular
Qmax update thereafter.
V at Chg Term Cell 0
4200
mV
Set to nominal cell voltage for a fully charged cell. The gauge will update this
parameter automatically each time full charge termination is detected.
Terminate Voltage
3200
mV
Set to empty point reference of battery based on system needs. Typical is
between 3000 and 3200 mV.
Ra Max Delta
44
mΩ
Set to 15% of Cell0 R_a 4 resistance after an optimization cycle is completed.
Charging Voltage
4200
mV
Set based on nominal charge voltage for the battery in normal conditions
(25°C, and so forth). Used as the reference point for offsetting by Taper
Voltage for full charge termination detection.
Taper Current
121
mA
Set to the nominal taper current of the charger + taper current tolerance to
ensure that the gauge will reliably detect charge termination.
Taper Voltage
100
mV
Sets the voltage window for qualifying full charge termination. Can be set
tighter to avoid or wider to ensure possibility of reporting 100% SOC in outer
JEITA temperature ranges that use derated charging voltage.
Dsg Current Threshold
60
mA
Sets threshold for gauge detecting battery discharge. Must be set lower than
minimal system load expected in the application and higher than Quit Current.
Chg Current Threshold
75
mA
Sets the threshold for detecting battery charge. Can be set higher or lower
depending on typical trickle charge current used. Also must be set higher than
Quit Current.
Quit Current
40
mA
Sets threshold for gauge detecting battery relaxation. Can be set higher or
lower depending on typical standby current and exhibited in the end system.
Avg I Last Run
–299
mA
Current profile used in capacity simulations at onset of discharge or at all times
if Load Select = 0. Must be set to nominal system load. Is automatically
updated by the gauge every cycle.
Avg P Last Run
–1131
mW
Power profile used in capacity simulations at onset of discharge or at all times
if Load Select = 0. Must be set to nominal system power. Is automatically
updated by the gauge every cycle.
Sleep Current
10
mA
Sets the threshold at which the fuel gauge enters SLEEP mode. Take care in
setting above typical standby currents else entry to SLEEP may be
unintentionally blocked.
22
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Typical Application (continued)
Table 5. Key Data Flash Parameters for Configuration (continued)
NAME
DEFAULT
UNIT
Charge T0
0
°C
Sets the boundary between charging inhibit and charging with T0 parameters.
Charge T1
10
°C
Sets the boundary between charging with T0 and T1 parameters.
Charge T2
45
°C
Sets the boundary between charging with T1 and T2 parameters.
Charge T3
50
°C
Sets the boundary between charging with T2 and T3 parameters.
Charge T4
60
°C
Sets the boundary between charging with T3 and T4 parameters.
Charge Current T0
50
% Des Cap
Sets the charge current parameter for T0.
Charge Current T1
100
% Des Cap
Sets the charge current parameter for T1.
Charge Current T2
100
% Des Cap
Sets the charge current parameter for T2.
Charge Current T3
100
% Des Cap
Sets the charge current parameter for T3.
Charge Current T4
0
% Des Cap
Sets the charge current parameter for T4.
Charge Voltage T0
262
16 mV
Sets the charge voltage parameter for T0.
Charge Voltage T1
262
16 mV
Sets the charge voltage parameter for T1.
Charge Voltage T2
259
16 mV
Sets the charge voltage parameter for T2.
Charge Voltage T3
256
16 mV
Sets the charge voltage parameter for T3.
Charge Voltage T4
0
16 mV
Sets the charge voltage parameter for T4.
Chg Temp Hys
5
°C
Adds temperature hysteresis for boundary crossings to avoid oscillation if
temperature is changing by a degree or so on a given boundary.
Chg Disabled
Regulation V
4200
mV
Sets the voltage threshold for voltage regulation to system when charge is
disabled. TI recommends programming to same value as Charging Voltage and
maximum charge voltage that is obtained from Charge Voltage Tn parameters.
CC Gain
10
mΩ
Calibrate this parameter using TI-supplied evaluation software and calibration
procedure in the TRM. Determines conversion of coulomb counter measured
sense resistor voltage to current.
CC Delta
10
mΩ
Calibrate this parameter using TI-supplied evaluation software and calibration
procedure in the TRM. Determines conversion of coulomb counter measured
sense resistor voltage to passed charge.
CC Offset
–1418
Counts
Calibrate this parameter using TI-supplied evaluation software and calibration
procedure in the TRM. Determines native offset of coulomb counter hardware
that must be removed from conversions.
Board Offset
0
Counts
Calibrate this parameter using TI-supplied evaluation software and calibration
procedure in the TRM. Determines native offset of the printed-circuit-board
parasitics that must be removed from conversions.
mV
Calibrate this parameter using TI-supplied evaluation software and calibration
procedure in the TRM. Determines voltage offset between cell tab and ADC
input node to incorporate back into or remove from measurement, depending
on polarity.
Pack V Offset
0
RECOMMENDED SETTING
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9.2.2 Detailed Design Procedure
9.2.2.1 BAT Voltage Sense Input
A ceramic capacitor at the input to the BAT pin is used to bypass AC voltage ripple to ground, greatly reducing
its influence on battery voltage measurements. It proves most effective in applications with load profiles that
exhibit high-frequency current pulses (that is, cell phones) but is recommended for use in all applications to
reduce noise on this sensitive high-impedance measurement node.
9.2.2.2 SRP and SRN Current Sense Inputs
The filter network at the input to the coulomb counter is intended to improve differential mode rejection of voltage
measured across the sense resistor. These components must be placed as close as possible to the coulomb
counter inputs and the routing of the differential traces length-matched to best minimize impedance mismatchinduced measurement errors.
9.2.2.3 Sense Resistor Selection
Any variation encountered in the resistance present between the SRP and SRN pins of the fuel gauge will affect
the resulting differential voltage, and derived current, it senses. As such, TI recommends selecting a sense
resistor with minimal tolerance and temperature coefficient of resistance (TCR) characteristics. The standard
recommendation based on best compromise between performance and price is a 1% tolerance, 100-ppm drift
sense resistor with a 1-W power rating.
9.2.2.4 TS Temperature Sense Input
Similar to the BAT pin, a ceramic decoupling capacitor for the TS pin is used to bypass AC voltage ripple away
from the high-impedance ADC input, minimizing measurement error. Another helpful advantage is that the
capacitor provides additional ESD protection, because the TS input to system may be accessible in systems that
use removable battery packs. The capacitor must be placed as close as possible to the respective input pin for
optimal filtering performance.
9.2.2.5 Thermistor Selection
The fuel gauge temperature sensing circuitry is designed to work with a negative temperature coefficient-type
(NTC) thermistor with a characteristic 10-kΩ resistance at room temperature (25°C). The default curve-fitting
coefficients configured in the fuel gauge specifically assume a 103AT-2 type thermistor profile and so that is the
default recommendation for thermistor selection purposes. Moving to a separate thermistor resistance profile (for
example, JT-2 or others) requires an update to the default thermistor coefficients in data flash to ensure highest
accuracy temperature measurement performance.
9.2.2.6 REGIN Power Supply Input Filtering
A ceramic capacitor is placed at the input to the fuel gauge internal LDO to increase power supply rejection
(PSR) and improve effective line regulation. It ensures that voltage ripple is rejected to ground instead of
coupling into the internal supply rails of the fuel gauge.
9.2.2.7 VCC LDO Output Filtering
A ceramic capacitor is also needed at the output of the internal LDO to provide a current reservoir for fuel gauge
load peaks during high peripheral utilization. It acts to stabilize the regulator output and reduce core voltage
ripple inside of the fuel gauge.
24
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9.2.3 Application Curves
8.8
VREGIN = 2.7 V
VREGIN = 4.5 V
2.6
fOSC - High Frequency Oscillator (MHz)
VREG25 - Regulator Output Voltage (V)
2.65
2.55
2.5
2.45
2.4
2.35
8.7
8.6
8.5
8.4
8.3
8.2
8.1
8
-40
Temperature (qC)
-20
0
20
40
Temperature (qC)
D001
34
5
33.5
4
33
32.5
32
31.5
31
30.5
30
-40
-20
0
20
40
Temperature (qC)
60
80
100
100
D002
3
2
1
0
-1
-2
-3
-4
-5
-30
-20
D003
Figure 15. Low-Frequency Oscillator Frequency vs
Temperature
80
Figure 14. High-Frequency Oscillator Frequency vs
Temperature
Reported Temperature Error (qC)
fLOSC - Low Frequency Oscillator (kHz)
Figure 13. Regulator Output Voltage vs Temperature
60
-10
0
10
20
30
Temperature (qC)
40
50
60
D004
Figure 16. Reported Internal Temperature Measurement vs
Temperature
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10 Power Supply Recommendations
10.1 Power Supply Decoupling
Both the REGIN input pin and the VCC output pin require low equivalent series resistance (ESR) ceramic
capacitors placed as close as possible to the respective pins to optimize ripple rejection and provide a stable and
dependable power rail that is resilient to line transients. A 0.1-μF capacitor at the REGIN and a 1-μF capacitor at
VCC will suffice for satisfactory device performance.
11 Layout
11.1 Layout Guidelines
11.1.1 Sense Resistor Connections
Kelvin connections at the sense resistor are just as critical as those for the battery terminals themselves. The
differential traces must be connected at the inside of the sense resistor pads and not anywhere along the highcurrent trace path to prevent false increases to measured current that could result when measuring between the
sum of the sense resistor and trace resistance between the tap points. In addition, the routing of these leads
from the sense resistor to the input filter network and finally into the SRP and SRN pins needs to be as closely
matched in length as possible else additional measurement offset could occur. It is further recommended to add
copper trace or pour-based "guard rings" around the perimeter of the filter network and coulomb counter inputs to
shield these sensitive pins from radiated EMI into the sense nodes. This prevents differential voltage shifts that
could be interpreted as real current change to the fuel gauge. All of the filter components need to be placed as
close as possible to the coulomb counter input pins.
11.1.2 Thermistor Connections
The thermistor sense input must include a ceramic bypass capacitor placed as close to the TS input pin as
possible. The capacitor helps to filter measurements of any stray transients as the voltage bias circuit pulses
periodically during temperature sensing windows.
11.1.3 High-Current and Low-Current Path Separation
For best possible noise performance, it is extremely important to separate the low-current and high-current loops
to different areas of the board layout. The fuel gauge and all support components must be situated on one side
of the boards and tap off of the high-current loop (for measurement purposes) at the sense resistor. Routing the
low-current ground around instead of under high-current traces will further help to improve noise rejection.
26
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11.2 Layout Example
Battery power
connection to
system
Use copper
pours for battery
power path to
minimize IR
losses
SCL
To system host
processor
SDA
BSDA
BATTERY PACK
CONNECTOR
To charger slave
BSCL
C1
PACK+
Kelvin connect the
BAT sense line right
at positive terminal to
battery pack
REGIN
BAT
C2
BI/TOUT
CE
Vcc
BSDA
VSS
VSS
SDA
BSCL
SRN
SCL
SOC_INT
SRP
C3
THERM
TS
INT
PACK –
10 mΩ 1%
Via connects to Power Ground
Ground return to
system
Kelvin connect SRP
and SRN
connections right at
Rsense terminals
Figure 17. Layout Schematic
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12 Device and Documentation Support
12.1 Documentation Support
12.1.1 Related Documentation
To obtain a copy of any of the following TI documents, go to the TI website at www.ti.com.
• bq27531-G1 Technical Reference Manual User's Guide (SLUUA96)
• bq27531EVM with bq27531 Battery Management Unit Impedance Track™ Fuel Gauge and bq24192 4.5-A,
Switch-Mode Battery Charger for Single-Cell Applications User's Guide (SLUUA90)
12.2 Community Resources
The following links connect to TI community resources. Linked contents are provided "AS IS" by the respective
contributors. They do not constitute TI specifications and do not necessarily reflect TI's views; see TI's Terms of
Use.
TI E2E™ Online Community TI's Engineer-to-Engineer (E2E) Community. Created to foster collaboration
among engineers. At e2e.ti.com, you can ask questions, share knowledge, explore ideas and help
solve problems with fellow engineers.
Design Support TI's Design Support Quickly find helpful E2E forums along with design support tools and
contact information for technical support.
12.3 Trademarks
Impedance Track, MaxLife, NanoFree, E2E are trademarks of Texas Instruments.
All other trademarks are the property of their respective owners.
12.4 Electrostatic Discharge Caution
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.
12.5 Glossary
SLYZ022 — TI Glossary.
This glossary lists and explains terms, acronyms, and definitions.
13 Mechanical, Packaging, and Orderable Information
The following pages include mechanical, packaging, and orderable information. This information is the most
current data available for the designated devices. This data is subject to change without notice and revision of
this document. For browser-based versions of this data sheet, refer to the left-hand navigation.
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PACKAGE OPTION ADDENDUM
www.ti.com
10-Dec-2020
PACKAGING INFORMATION
Orderable Device
Status
(1)
Package Type Package Pins Package
Drawing
Qty
Eco Plan
(2)
Lead finish/
Ball material
MSL Peak Temp
Op Temp (°C)
Device Marking
(3)
(4/5)
(6)
BQ27531YZFR-G1
ACTIVE
DSBGA
YZF
15
3000
RoHS & Green
SNAGCU
Level-1-260C-UNLIM
-40 to 85
BQ27531
BQ27531YZFT-G1
ACTIVE
DSBGA
YZF
15
250
RoHS & Green
SNAGCU
Level-1-260C-UNLIM
-40 to 85
BQ27531
(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)
RoHS: TI defines "RoHS" to mean semiconductor products that are compliant with the current EU RoHS requirements for all 10 RoHS substances, including the requirement that RoHS substance
do not exceed 0.1% by weight in homogeneous materials. Where designed to be soldered at high temperatures, "RoHS" products are suitable for use in specified lead-free processes. TI may
reference these types of products as "Pb-Free".
RoHS Exempt: TI defines "RoHS Exempt" to mean products that contain lead but are compliant with EU RoHS pursuant to a specific EU RoHS exemption.
Green: TI defines "Green" to mean the content of Chlorine (Cl) and Bromine (Br) based flame retardants meet JS709B low halogen requirements of
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