Texas Instruments | BQ35100 Lithium Primary Battery Fuel Gauge and End-Of-Service Monitor (Rev. E) | Datasheet | Texas Instruments BQ35100 Lithium Primary Battery Fuel Gauge and End-Of-Service Monitor (Rev. E) Datasheet

Texas Instruments BQ35100 Lithium Primary Battery Fuel Gauge and End-Of-Service Monitor (Rev. E) Datasheet
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BQ35100
SLUSCM6E – JUNE 2016 – REVISED APRIL 2019
BQ35100 Lithium Primary Battery Fuel Gauge and End-Of-Service Monitor
1 Features
3 Description
•
The BQ35100 Battery Fuel Gauge and End-OfService Monitor provides highly configurable fuel
gauging for non-rechargeable (primary) lithium
batteries without requiring a forced discharge of the
battery. Built so that optimization is not necessary to
achieve accurate gauging, the BQ35100 device uses
patented TI gauging algorithms to support the option
to seamlessly replace an old battery with a new one.
1
•
•
Fuel gauge and battery diagnostics for flow meter
applications predict end-of-service or early battery
failure
– Supports lithium thionyl chloride (Li-SOCl2)
and lithium manganese dioxide (Li-MnO2)
chemistry batteries
– Accurate voltage, temperature, current, and
coulomb counter measurements that report
battery health and service life
– State-of-health (SOH) algorithm for Li-MnO2
– End-of-service (EOS algorithm for Li-SOCl2)
– Coulomb accumulation (ACC) algorithm for all
battery types
Ultra-low average power consumption to
maximize battery run time
– Gauge enabled through host-controlled
periodic updates
– State-of-health (SOH) ~0.06 µA
– End-of-service (EOS) ~0.35 µA
– Coulomb accumulation (ACC) diagnostic
updates ~0.3 µA
System interaction capabilities
– I2C host communication, providing battery
parameter and status access
– Configurable host interrupt
– Battery information data logging options for in
operation diagnostics and failure analysis
– SHA-1 authentication to help prevent
counterfeit battery use
The BQ35100 device provides accurate results with
ultra-low average power consumption where less
than 2 µA can be achieved through host control via
the GAUGE ENABLE (GE) pin. The device is only
required to be powered long enough, at a systemdetermined update frequency, to gather data and to
make calculations to support the selected algorithm.
A typical system may need to only be updated once
every 8 hours as the gauge is not required to be
powered to measure all discharge activity.
The fuel gauging functions use voltage, current, and
temperature measurements to provide state-of-health
(SOH) data and end-of-service (EOS) warning
information where the host can read the gathered
data through a 400-kHz I2C bus. An ALERT output,
based on a variety of configurable status and data
options, is also available to interrupt the host.
Device Information(1)
PART NUMBER
PACKAGE
BQ35100
TSSOP (14)
BODY SIZE (NOM)
5.00 mm × 4.40 mm
(1) For all available packages, see the orderable addendum at
the end of the data sheet.
Simplified Schematic
BAT+
2 Applications
•
•
•
Used in primary battery systems and suitable for
dynamic load and large ambient temperature
change applications
– Smart meters and flow meters
– Door access control
– Smoke and gas leak detectors
– Building automation
– IoT, including sensor nodes
– Asset tracking
Battery status reporting and diagnostics with early
failure detection for flow meter systems
Extends battery runtime with accurate battery
gauging for smoke detector, sensor node, and
asset tracker applications
REGIN
I2C CLK
10 k 10 k
I2C DATA
REG25
ALERT
1 VIN
100k
100
SDA 14
2 ALERT
SCL 13
3 NC
VEN 12
REG 25
10k NTC
4 BAT
GAUGE ENABLE
TS 11
0.1 µF
REGIN
VSUPPLY 1 M
REG25
1 µF
5 GE
SRN 10
6 REGIN
SRP 9
7 REG25
VSS 8
0.1 µF
0.1 µF
100
0.1
75 ppm
100
0.1 µF
1 µF
PACK–
Copyright © 2017, Texas Instruments Incorporated
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.
BQ35100
SLUSCM6E – JUNE 2016 – REVISED APRIL 2019
www.ti.com
Table of Contents
1
2
3
4
5
6
Features ..................................................................
Applications ...........................................................
Description .............................................................
Revision History.....................................................
Pin Configuration and Functions .........................
Specifications.........................................................
6.1
6.2
6.3
6.4
6.5
6.6
6.7
6.8
6.9
6.10
6.11
6.12
6.13
6.14
6.15
1
1
1
2
4
5
Absolute Maximum Ratings ...................................... 5
ESD Ratings.............................................................. 5
Recommended Operating Conditions....................... 5
Thermal Information .................................................. 6
Power Supply Current Static Modes ......................... 6
Digital Input and Outputs ......................................... 6
Power-On Reset........................................................ 7
LDO Regulator .......................................................... 7
Internal Temperature Sensor .................................... 7
Internal Clock Oscillators ....................................... 7
Integrating ADC (Coulomb Counter)....................... 7
ADC (Temperature and Voltage Measurements) ... 8
Data Flash Memory................................................. 8
I2C-Compatible Interface Timing Characteristics .... 8
Typical Characteristics ........................................... 9
7
Detailed Description ............................................ 10
7.1
7.2
7.3
7.4
8
Overview .................................................................
Functional Block Diagram ......................................
Feature Description.................................................
Device Functional Modes........................................
10
10
10
15
Application and Implementation ........................ 17
8.1 Application Information .......................................... 17
8.2 Typical Applications ................................................ 17
9 Power Supply Recommendations...................... 21
10 Layout................................................................... 22
10.1 Layout Guidelines ................................................. 22
10.2 Layout Example .................................................... 22
10.3 ESD Spark Gap .................................................... 24
11 Device and Documentation Support ................. 25
11.1
11.2
11.3
11.4
11.5
11.6
Documentation Support ........................................
Receiving Notification of Documentation Updates
Community Resources..........................................
Trademarks ...........................................................
Electrostatic Discharge Caution ............................
Glossary ................................................................
25
25
25
25
25
25
12 Mechanical, Packaging, and Orderable
Information ........................................................... 25
4 Revision History
Changes from Revision D (May 2018) to Revision E
•
Page
Corrected a typo in Features ................................................................................................................................................. 1
Changes from Revision C (September 2017) to Revision D
Page
•
Added further information to Features and Applications ........................................................................................................ 1
•
Changed Recommended Operating Conditions .................................................................................................................... 5
•
Added Power Supply Current Static Modes ........................................................................................................................... 6
•
Changed Basic Measurement Systems ............................................................................................................................... 10
•
Changed Device Functional Modes ..................................................................................................................................... 15
•
Added EOS Mode Load Pulse Synchronization................................................................................................................... 20
•
Added Benefits of the bq35100 Gauge Compared to Alternative Monitoring Techniques .................................................. 20
Changes from Revision B (September 2016) to Revision C
Page
•
Changed Features, Applications, and Description ................................................................................................................ 1
•
Added Preparation for Gauging ........................................................................................................................................... 18
•
Changed Detailed Design Procedure .................................................................................................................................. 18
•
Added Using the bq35100 with a Battery and Capacitor in Parallel ................................................................................... 20
2
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Changes from Revision A (July 2016) to Revision B
Page
•
Changed Device Information ................................................................................................................................................. 1
•
Changed Specifications ......................................................................................................................................................... 5
•
Changed Application Curves ............................................................................................................................................... 21
•
Changed VCC to VREG25 in Layout Guidelines ...................................................................................................................... 22
•
Changed VCC to VREG25 in Board Offset Considerations ..................................................................................................... 23
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BQ35100
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5 Pin Configuration and Functions
TSSOP (PW) Package
14-Pin
Top View
VIN
1
14
SDA
ALERT
2
13
SCL
NC
3
12
VEN
BAT
4
11
TS
GE
5
10
SRN
REGIN
6
9
SRP
REG25
7
8
V
SS
Not to scale
Pin Functions
(1)
4
NUMBER
NAME
I/O
1
VIN
AI (1)
DESCRIPTION
2
ALERT
O
Active low interrupt open-drain output. Requires an external pullup
3
NC
—
Not used and should be connected to VSS.
4
BAT
P
Voltage measurement input and can be left floating or tied to VSS if not used.
5
GE
I
Gauge enable. Internal LDO is disconnected from REGIN when driven low.
6
REGIN
P
Internal integrated LDO input. Decouple with 0.1-µF ceramic capacitor to VSS.
7
REG25
P
2.5-V output voltage of the internal integrated LDO. Decouple with 1-µF ceramic capacitor
VSS.
8
VSS
P
Device ground
9
SRP
I
Analog input pin connected to the internal coulomb-counter peripheral for integrating a small
voltage between SRP and SRN where SRP is nearest the BAT– connection.
10
SRN
I
Analog input pin connected to the internal coulomb-counter peripheral for integrating a small
voltage between SRP and SRN where SRN is nearest the PACK– connection.
Optional voltage measurement input
11
TS
I
Pack thermistor voltage sense (use 103AT-type thermistor)
12
VEN
O
Optional open-drain external voltage divider control output
13
SCL
I
Slave I2C serial communication clock input. Use with a 10-K pullup resistor (typical).
14
SDA
I/O
Open-drain slave I2C serial communication data line. Use with a 10-kΩ pullup resistor
(typical).
P = Power Connection, O = Digital Output, AI = Analog Input, I = Digital Input, I/OD = Digital Input/Output
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6 Specifications
6.1 Absolute Maximum Ratings
Over-operating free-air temperature range (unless otherwise noted) (1)
MIN
MAX
UNIT
VREGIN
Regulator Input Range
–0.3
5.5
V
VREG25
Supply Voltage Range
–0.3
2.75
V
Open-drain I/O pins (SDA, SCL, VEN)
–0.3
5.5
V
Open-drain I/O pins (ALERT)
–0.3
2.75
V
VBAT
BAT Input Pin
–0.3
5.5
V
VI
Input voltage range (SRN, SRP, TS)
–0.3
VREG25 + 0.3
V
TA
Operating free-air temperature range
–40
85
°C
TF
Functional Temperature Range
–40
100
°C
Storage temperature range
–65
150
°C
Lead temperature (soldering, 10 s)
–40
100
°C
VIOD
TSTG
(1)
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.
6.2 ESD Ratings
VALUE
V(ESD)
Electrostatic
discharge
Human Body Model (HBM), per ANSI/ESDA/JEDEC JS-001 (1), BAT pin
±1500
Human Body Model (HBM), per ANSI/ESDA/JEDEC JS-001 (1), all other pins
±2000
Charged-device model (CDM), per JEDEC specification JESD22-C101
(1)
(2)
(2)
UNIT
V
±500
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.
6.3 Recommended Operating Conditions
TA =–40°C to 85°C; Typical Values at TA = 25°C CLDO25 = 1.0 μF, and VREGIN = 3.6 V (unless otherwise noted)
MIN
VREGIN
CREGIN
CLDO25
Supply Voltage
No operating restrictions
No FLASH writes
External input capacitor
for internal LDO
between REGIN and
Nominal capacitor values specified.
VSS
Recommend a 10% ceramic X5R type
capacitor located close to the device.
External output
capacitor for internal
LDO between VREG25
NOM
MAX
UNIT
2.7
4.5
V
2.45
2.7
V
0.47
0.1
µF
1
µF
0.05
µA
0.3
µA
ICC_GELOW (1)
Gas gauge in Disabled
mode
ICC_ACC_AVE (1)
Gas gauge in
ACCUMULATOR mode Update every 30 minutes otherwise GE = Low
average current
ICC_SOH_AVE (1)
State-of-health average
Update every 8 hours otherwise GE = Low
current
0.06
µA
ICC_EOS_AVE (1)
End-of-service average Update every 8 hours 3- s Load Pulse
current
otherwise GE = Low
0.35
µA
VA1
Input voltage range
(VIN, TS)
VSS – 0.05
1
V
VA2
Input voltage range
(BAT)
VSS – 0.125
5.0
V
(1)
GE = Low
Not production tested
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Recommended Operating Conditions (continued)
TA =–40°C to 85°C; Typical Values at TA = 25°C CLDO25 = 1.0 μF, and VREGIN = 3.6 V (unless otherwise noted)
MIN
VA3
Input voltage range
(SRP, SRN)
ILKG
Input leakage current
(I/O pins)
tPUCD
Power-up
communication
NOM
VSS – 0.125
MAX
UNIT
0.125
V
0.3
µA
250
ms
6.4 Thermal Information
BQ35100
THERMAL METRIC (1)
TSSOP (PW)
UNIT
14 PINS
RθJA, High K
Junction-to-ambient thermal resistance
103.8
°C/W
RθJC(top)
Junction-to-case(top) thermal resistance
31.9
°C/W
RθJB
Junction-to-board thermal resistance
46.6
°C/W
ψJT
Junction-to-top characterization parameter
2.0
°C/W
ψJB
Junction-to-board characterization parameter
45.9
°C/W
RθJC(bottom)
Junction-to-case(bottom) thermal resistance
N/A
°C/W
(1)
For more information about traditional and new thermal metrics, see the Semiconductor and IC Package Thermal Metrics application
report, SPRA953.
6.5 Power Supply Current Static Modes
over operating free-air temperature range (unless otherwise noted)
PARAMETER
TEST CONDITIONS
MIN
TYP
MAX
UNIT
ICC_ACCU (1)
Gas gauge in
ACCUMULATOR mode
GE = High AND GaugeStart()
received and GaugeStop() not
Received (GMSEL1,0 = 0,0)
130
µA
ICC_SOH (1)
State-of-health operating
current
GE = High AND GaugeStart()
received and GaugeStop() not
Received (GMSEL1,0 = 0,1)
40
µA
ICC_EOS_Burst (1)
End-of-service operating
current—data burst
GE = High AND GaugeStart()
received and GaugeStop() not
Received (GMSEL1,0 = 1,0)
315
µA
ICC_EOS_Gather (1)
End-of-service operating
current—data gathering
GE = High AND GaugeStart() AND
GaugeStop() Received (GMSEL1,0
= 1,0)
75
µA
ICC_GELOW (1)
Device Disabled
GE = LOW
0.05
µA
(1)
Not production tested
6.6 Digital Input and Outputs
PARAMETER
TEST CONDITIONS
MIN
TYP
MAX
UNIT
VOL
Output voltage low (SDA, SCL,
VEN)
IOL = 3 mA
VOH(PP)
Output high voltage
IOH = –1 mA
VREG25 – 0.5
V
VOH(OD)
Output high voltage (SDA, SCL,
VEN, ALERT)
External pullup resistor connected to
VREG25
VREG25 – 0.5
V
VIL
Input voltage low (SDA, SCL)
–0.3
0.6
V
VIH
Input voltage high (SDA, SCL)
1.2
5.5
V
VIL(GE)
GE Low-level input voltage
VIH(GE)
GE High-level input voltage
Ilkg
Input leakage current (I/O pins)
6
VREGIN = 2.8 to 4.5 V
0.4
0.8
2.65
0.3
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V
V
μA
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6.7 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 REG25
VHYS
Power-on reset hysteresis
TEST CONDITIONS
MIN
TYP
MAX
UNIT
2.05
2.20
2.31
V
115
mV
6.8 LDO Regulator
TA = 25°C, CLDO25 = 1.0 μF, VREGIN = 3.6 V (unless otherwise noted) (1)
PARAMETER
VREG25
ISHORT (2)
(1)
(2)
Regulator output voltage
Short circuit current limit
TEST CONDITIONS
MIN
TYP
MAX
2.7 V ≤ VREGIN ≤ 4.5 V, IOUT ≤ 16 mA TA = –40°C
to 85°C
2.3
2.5
2.7
2.45 V ≤ VREGIN < 2.7 V, IOUT ≤ 3 mA TA =
–40°C to 85°C
2.3
UNIT
V
VREG25 = 0 V
TA = –40°C to 85°C
250
mA
LDO output current, IOUT, is the sum of internal and external load currents.
Specified by design. Not production tested.
6.9 Internal Temperature Sensor
TA = –40°C to 85°C, 2.4 V < REG25 < 2.6 V; Typical Values at TA = 25°C and REG25 = 2.5 V (unless otherwise noted)
PARAMETER
GTEMP
TEST CONDITIONS
MIN
Internal temperature sensor
voltage gain
TYP
MAX
–2
UNIT
mV/°C
6.10 Internal Clock Oscillators
TA = –40°C to 85°C, 2.4 V < REG25 < 2.6 V; Typical Values at TA = 25°C and REG25 = 2.5 V (unless otherwise noted)
PARAMETER
TEST CONDITIONS
MIN
TYP
MAX
UNIT
f(LOSC)
Operating frequency
32.768
kHz
f(OSC)
Operating frequency
2.097
MHz
t(SXO)
Start-up time (1)
(1)
2.5
5
ms
The startup time is defined as the time it takes for the oscillator output frequency to be ±3%.
6.11 Integrating ADC (Coulomb Counter)
TA = –40°C to 85°C, 2.4 V < REG25 < 2.6 V; Typical Values at TA = 25°C and REG25 = 2.5 V (unless otherwise noted)
PARAMETER
V(SR)
tSR_CONV
Input voltage range,
V(SRN) and V(SRP)
V(SR) = V(SRN) – V(SRP)
Conversion time
Single conversion
Resolution
VOS(SR)
Input offset
INL
Integral nonlinearity
error
ZIN(SR)
Effective input
resistance (2)
ILKG(SR)
Input leakage
current (2)
(1)
(2)
TEST CONDITIONS
MIN
TYP
–0.125
MAX
UNIT
0.125
V
1
14
s
15
10
bits
µV
FSR (1)
±0.007%
2.5
MΩ
0.3
µA
Full-scale reference
Specified by design. Not tested in production.
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6.12 ADC (Temperature and Voltage Measurements)
TA = –40°C to 85°C, 2.4 V < REG25 < 2.6 V; Typical Values at TA = 25°C and REG25 = 2.5 V (unless otherwise noted)
PARAMETER
TEST CONDITIONS
MIN
TYP
MAX
VIN(BAT)
BAT Input range
VSS – 0.125
5
VIN(TSAT)
TS Input range
VSS – 0.125
VREG25
tSR_CONV
Conversion time
Resolution
Input offset
ZADC1
Effective input
resistance(TS) (1)
ZADC2
Effective input
resistance(BAT) (1)
ILKG(ADC)
Input leakage
current (1)
V
V
125
14
VOS(SR)
(1)
Single conversion
UNIT
ms
15
bits
1
With internal pull-down activated
5
When not measuring
8
During measurement
µV
kΩ
MΩ
100
kΩ
0.3
µA
Specified by design. Not tested in production.
6.13 Data Flash Memory
TA = –40°C to 85°C, 2.4 V < REG25 < 2.6 V; Typical Values at TA = 25°C and REG25 = 2.5 V (unless otherwise noted)
PARAMETER
TEST CONDITIONS
Data retention
tDR
(1)
Flash-programming write cycles (1)
tWORDPROG
Word programming time (1)
ICCPROG
Flash-write supply current (1)
(1)
MIN
TYP
MAX
UNIT
10
Years
20,000
Cycles
5
2
ms
10
mA
Specified by design. Not tested in production.
6.14 I2C-Compatible Interface Timing Characteristics
TA = –40°C to 85°C, 2.45 V < VREGIN = VBAT < 5.5 V; Typical Values at TA = 25°C and VBAT = 3.6 V (unless otherwise noted)
MIN
NOM
MAX
UNIT
tR
SCL/SDA rise time
300
ns
tF
SCL/SDA fall time
300
ns
tW(H)
SCL pulse width (high)
600
ns
tW(L)
SCL pulse width (low)
1.3
µs
tSU(STA)
Setup for repeated start
600
ns
td(STA)
Start to first falling edge of SCL
600
ns
tSU(DAT)
Data setup time
100
ns
th(DAT)
Data hold time
tSU(STOP)
Setup time for stop
tBUF
Bus free time between stop and start
fSCL
Clock frequency
8
0
ns
600
ns
66
µs
400
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tSU(STA)
tw(H)
tf
tw(L)
tr
t(BUF)
SCL
SDA
td(STA)
tsu(STOP)
tf
tr
th(DAT)
tsu(DAT)
REPEATED
START
STOP
START
Figure 1. I2C-Compatible Interface Timing Diagrams
6.15 Typical Characteristics
15
25
20
10
Current Error (mA)
Voltage Error (mV)
15
5
0
-5
-10
10
5
0
-5
-10
-15
-15
-20
2800
-40qC
-20qC
3000
3200
25qC
65qC
85qC
-40qC
-20qC
-20
3400 3600 3800
Battery Voltage (mV)
4000
4200
4400
-25
-3000
-2000
25qC
65qC
-1000
D001
Figure 2. V(Err) Across VIN (0 mA)
85qC
0
1000
Current (mA)
2000
3000
D003
Figure 3. I(Err)
2
1
Temperature Error (qC)
0
-1
-2
-3
-4
-5
-6
-7
-8
-9
-40
-20
0
20
40
Temperature (qC)
60
80
100
D004
Figure 4. T(Err)
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7 Detailed Description
7.1 Overview
The BQ35100 Battery Fuel Gauge and End-Of-Service Monitor provides gas gauging for lithium thionyl
chloride (Li-SOCl2) and lithium manganese dioxide (Li-MnO2) primary batteries without requiring any forced
discharge of the battery. The lithium primary gas gauging function uses voltage, current, and temperature
data to provide state-of-health (SOH) and end-of-service (EOS) data.
7.2 Functional Block Diagram
REGIN
GE
2.5-V LDO
+
Power Mgmt
REG25
Oscillator
System Clock
Divider
BAT
VIN
ADC
TS
Temp
Sensor
SDA
SCL
I2C
Communications
Gauging
Algorithm
Coulomb
Counter
SRP
SRN
VEN
Peripherals
ALERT
Data
Memory
NC
VSS
Program
Memory
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7.3 Feature Description
7.3.1 Basic Measurement Systems
7.3.1.1 Voltage
The device measures the BAT input using the integrated delta-sigma ADC, which is scaled by the internal
translation network, through the ADC. The translation gain function is determined by a calibration process.
In systems where the battery voltage is greater than VIN(BAT) MAX (for example, 2-series cell or more), then an
external voltage scaling circuit is required. The firmware then scales this <1 V value to reflect an average cell
value and then again by the number of series cells to reflect the full battery voltage value.
7.3.1.2 Temperature
The device can measure temperature through an integrated temperature sensor or an external NTC thermistor
using the integrated delta-sigma ADC. Only one source can be used and the selection is made by setting
Operation Config A [TEMPS] appropriately. The resulting measured temperature is available through the
Temperature() command. The internal temperature sensor result is also available through the
InternalTemperature() command.
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Feature Description (continued)
7.3.1.3 Coulombs
The integrating delta-sigma ADC (coulomb counter) in the device measures the discharge flow of the battery by
measuring the voltage drop across a small-value sense resistor between the SRP and SRN pins.
The 15-bit integrating ADC measures bipolar signals from –0.125 V to 0.125 V. The device continuously monitors
the measured current and integrates this value over time using an internal counter.
7.3.1.4 Current
For the primary battery current, the integrating delta-sigma ADC in the device measures the discharge current of
the battery by measuring the voltage drop across a small-value sense resistor between the SRP and SRN pins,
and is available through the Current() command.
The measured current also includes the current consumed by the device. To subtract this value from the reported
current, a value programmed in EOS Gauge Load Current is subtracted for improved accuracy.
7.3.2 Battery Gauging
The BQ35100 device can operate in three distinct modes: ACCUMULATOR (ACC) mode, STATE-OF-HEALTH
(SOH) mode, and END-OF-SERVICE (EOS) mode. The device can be configured and used for only one of these
modes in the field, as it is not intended to be able to actively switch between modes when in normal use.
7.3.2.1 ACCUMULATOR (ACC) Mode
In this mode, the BQ35100 device measures and updates cell voltage, cell temperature, and load current every
1 s. This data is provided through the I2C interface while ControlStatus()[GA] is set. To begin accumulation, the
GAUGE_START command should be sent, and when accumulation ends, the GAUGE_STOP command should
be sent. To ensure that no data is lost, the host should wait until G_DONE is set before powering down the
device.
7.3.2.2 STATE-OF-HEALTH (SOH) Mode
This mode is suitable for determining SOH for lithium manganese dioxide (Li-MnO2) chemistry. In this mode, cell
voltage and temperature are precisely measured immediately after the GE pin is asserted. The gauge uses this
data to compute SOH. Once the initial update occurs and the host reads the updated SOH, then the device can
be powered down.
7.3.2.2.1 Low State-of-Health Alert
BatteryStatus()[SOH_LOW] is set when StateOfCharge() is less than or equal to the value programmed in
SOHLOW.
7.3.2.3 END-OF-SERVICE (EOS) Mode
This mode is suitable for gauging lithium thionyl chloride (Li-SOCl2) cells. The end-of-service (EOS) gauging
algorithm uses voltage, current, and temperature data to determine the resistance (R) and rate of change of
resistance of the battery. The resistance data is then used to find Depth of Discharge (DOD) = DOD(R). As
above, SOH is determined and in turn used to determine the EOS condition.
7.3.2.3.1 Initial EOS Learning
For optimal accuracy, the first event where the device updates its impedance value is required to be when the
battery is full (a fresh battery). If the battery is partially discharged, then the accuracy of the EOS detection is
compromised.
When a new battery is inserted, then the NEW_BATTERY() command should be sent to the device to ensure the
initial learned resistance RNEW is refreshed correctly.
7.3.2.3.1.1 End-Of-Service Detection
The BQ35100 device can detect when a sharp increase in the trend of tracked impedance occurs, indicating that
the battery is reaching its EOS condition.
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Feature Description (continued)
7.3.3 Power Control
The BQ35100 device only has one active power mode that is enabled through the GAUGE ENABLE (GE) pin.
The power consumption of the BQ35100 device can change significantly based on host commands it receives
and its default configuration, specifically with respect to data flash updates.
For information on how to configure the device to influence the average power consumption, see the Power
Control section in the BQ35100 Technical Reference Manual (SLUUBH1).
7.3.4 Battery Condition Warnings
7.3.4.1 Battery Low Warning
The BQ35100 device can indicate and optionally trigger the ALERT pin when the primary battery voltage falls
below a programmable threshold.
7.3.4.2 Temperature Low Warning
The BQ35100 device can indicate and optionally trigger the ALERT pin when the primary battery temperature
falls below a programmable threshold.
7.3.4.3 Temperature High Warning
The BQ35100 device can indicate and optionally trigger the ALERT pin when the primary battery temperature
rises above a programmable threshold.
7.3.4.4
Battery Low SOH Warning
The BQ35100 device can indicate and optionally trigger the ALERT pin when the primary battery state-of-health
(SOH) falls below a programmable threshold.
7.3.4.5 Battery EOS OCV BAD Warning
The device assumes that when GE is asserted the cell is at rest and uses the initialization voltage reading to
determine the Open Circuit Voltage (OCV). If the cell were not fully relaxed at that point, then the voltage after
the pulse could rise above the OCV. This causes an incorrect impedance to be calculated.
7.3.5 ALERT Signal
The ALERT signal can be configured to be triggered by a variety of status conditions. When the ALERT
Configuration bit is set AND the corresponding bit in BatteryStatus() or ControlStatus() is set, then the
corresponding BatteryAlert() bit is set, triggering the ALERT signal.
7.3.6 Lifetime Data Collection
The BQ35100 device can be enabled by writing to Control() 0x002E [LT_EN] to gather data regarding the
primary battery and store it to data flash.
The following data is collected in RAM and only written to DF when the host sends the End command to the
device:
• Max and Min Cell Voltage
• Max and Min Discharge Current
• Max and Min Temperature
7.3.7 SHA-1 Authentication
As of March 2012, the latest revision is FIPS 180-4. SHA-1, or secure hash algorithm, is used to compute a
condensed representation of a message or data also known as hash. For messages < 264, the SHA-1 algorithm
produces a 160-bit output called a digest.
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Feature Description (continued)
In a SHA-1 one-way hash function, there is no known mathematical method of computing the input given, only
the output. The specification of SHA-1, as defined by FIPS 180-4, states that the input consists of 512-bit blocks
with a total input length less than 264 bits. Inputs that do not conform to integer multiples of 512-bit blocks are
padded before any block is input to the hash function. The SHA-1 algorithm outputs the 160-bit digest.
The device generates a SHA-1 input block of 288 bits (total input = 160-bit message + 128-bit key). To complete
the 512-bit block size requirement of the SHA-1 function, the device pads the key and message with a 1,
followed by 159 0s, followed by the 64 bit value for 288 (000...00100100000), which conforms to the pad
requirements specified by FIPS 180-4.
•
•
•
http://www.nist.gov/itl/
http://csrc.nist.gov/publications/fips
www.faqs.org/rfcs/rfc3174.html
7.3.8 Data Commands
7.3.8.1 Command Summary
Table 1. Command Summary Table
(1)
Cmd
Mode
Name
Format
Size in
Bytes
Min Value
Max Value
Default
Value
Unit
0x00...0x01
R/W
Control
Hex
2
0x00
0xff
—
—
0x02…0x05
R
AccumulatedCapacity
Integer
4
0
4.29e9
—
µAh
0x06…0x07
R
Temperature
Signed Int
2
–32768
32767
—
0.1 K
0x08...0x09
R
Voltage
Integer
2
0
65535
—
mV
0x0A
R
BatteryStatus
Hex
1
0x00
0xff
—
—
0x0B
R
BatteryAlert
Hex
1
0x00
0xff
—
—
0x0C…0x0D
R
Current
Signed Integer
2
–32768
32767
—
mA
0x16…0x17
R
Scaled R
Integer
2
0
65535
—
mΩ
0x22…0x23
R
Measured Z
Integer
2
0
65535
—
mΩ
0x28…0x29
R
InternalTemperature
Signed Integer
2
–32768
32767
—
0.1 K
0x2E…0x2F
R
StateOfHealth
Integer
1
0
100
—
%
0x3C…0x3D
R
DesignCapacity
Integer
2
0
65535
—
mAh
0x79
R
Cal_Count
Hex
1
0x00
0xff
—
0x7a…0x7B
R
Cal_Current
Signed Int
2
0
65535
—
mA
0x7C…0x7D
R
Cal_Voltage
Integer
2
0
65535
—
mV or
Counts (1)
0x7E…0x7F
R
Cal_Temperature
Integer
2
0
65535
—
K
mV when [EXTVCELL] = 0, and ADC counts when [EXTVCELL] = 1.
7.3.8.2 0x00, 0x01 AltManufacturerAccess() and 0x3E, 0x3F AltManufacturerAccess()
AltManufacturerAccess() provides a method of reading and writing data in the Manufacturer Access System
(MAC). The MAC command is sent via AltManufacturerAccess() by a block protocol. The result is returned on
AltManufacturerAccess() via a block read.
Commands are set by writing to registers 0x00/0x01. On a valid word access, the MAC command state is set,
and commands 0x3E and 0x3F are used for MAC commands. These new addresses work the same as 0x00 and
0x01, but are primarily intended for block writes and reads.
7.3.8.3 Control(): 0x00/0x01
Issuing a Control() command requires a subsequent two-byte subcommand. These additional bytes specify the
particular control function desired. The Control() command allows the host to control specific features of the
device during normal operation, and additional features when the BQ35100 device is in different access modes,
as described in Table 2.
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Table 2. Control Functions
CNTL DATA
SEALED ACCESS
CONTROL_STATUS
CNTL FUNCTION
0x0000
Yes
Reports the status of key features
DESCRIPTION
DEVICE_TYPE
0x0001
Yes
Reports the device type of 0x40 (indicating
BQ35100)
FW_VERSION
0x0002
Yes
Reports the firmware version on the device type
HW_VERSION
0x0003
Yes
Reports the hardware version of the device type
STATIC_CHEM_CHKSUM
0x0005
Yes
Calculates chemistry checksum
CHEM_ID
0x0006
Yes
Reports the chemical identifier used by the gas
gauge algorithms
PREV_MACWRITE
0x0007
Yes
Returns previous Control() command code
BOARD_OFFSET
0x0009
Yes
Forces the device to measure and store the board
offset
CC_OFFSET
0x000A
Yes
Forces the device to measure the internal CC offset
CC_OFFSET_SAVE
0x000B
Yes
Forces the device to store the internal CC offset
DF_VERSION
0x000C
Yes
Reports the data flash version on the device
GAUGE_START
0x0011
Yes
Triggers the device to enter ACTIVE mode
GAUGE_STOP
0x0012
Yes
Triggers the device to stop gauging and complete all
outstanding tasks
SELAED
0x0020
No
Places the device in SEALED access mode
CAL_ENABLE
0x002D
No
Toggle CALIBRATION mode enable
LT_ENABLE
0x002E
No
Enables Lifetime Data collection
RESET
0x0041
No
Forces a full reset of the device
EXIT_CAL
0x0080
No
Exit CALIBRATION mode
ENTER_CAL
0x0081
No
Enter CALIBRATION mode
NEW_BATTERY
0xa613
Yes
This is used to refresh the gauge when a new battery
is installed and resets all recorded data.
7.3.9 Communications
7.3.9.1 I2C Interface
The gas gauge supports the standard I2C read, incremental read, one-byte write quick read, and functions. The
7-bit device address (ADDR) is the most significant 7 bits of the hex address and is fixed as 1010101. The 8-bit
device address is therefore 0xAA or 0xAB for write or read, respectively.
Host Generated
S
0 A
ADDR[6:0]
Fuel Gauge Generated
CMD[7:0]
A
A P
DATA[7:0]
S
ADDR[6:0]
(a) 1-byte write
S
ADDR[6:0]
0 A
CMD[7:0]
1
A
DATA[7:0]
N P
(b) quick read
A Sr
ADDR[6:0]
1
A
DATA[7:0]
N P
...
DATA[7:0]
(c) 1-byte read
S
ADDR[6:0]
0 A
CMD[7:0]
A Sr
ADDR[6:0]
1
A
DATA[7:0]
A
N P
(d) incremental read
Figure 5. Supported I2C Formats: (a) 1-Byte Write, (b) Quick Read, (c) 1 Byte-read, and (d) Incremental
Read (S = Start, Sr = Repeated Start, A = Acknowledge, N = No Acknowledge, and P = Stop).
The “quick read” returns data at the address indicated by the address pointer. The address pointer, a register
internal to the I2C communication engine, increments whenever data is acknowledged by the device 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 2-byte commands that require two bytes of data).
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S
ADDR[6:0]
0
A
A
CMD[7:0]
A
DATA[7:0]
P
Figure 6. Attempt To Write a Read-Only Address (Nack After Data Sent By Master)
S
0
ADDR[6:0]
CMD[7:0]
A
N P
Figure 7. Attempt To Read an Address Above 0x7F (Nack Command)
S
ADDR[6:0]
CMD[7:0]
0 A
A
DATA[7:0]
A
DATA[7:0]
N
...
N P
Figure 8. Attempt at Incremental Writes (Nack All Extra Data Bytes Sent)
S
ADDR[6:0]
0 A
A Sr
CMD[7:0]
ADDR[6:0]
1
A
DATA[7:0]
Address
0x7F
A
...
DATA[7:0]
Data From
addr 0x7F
N P
Data From
addr 0x00
Figure 9. Incremental Read at the Maximum Allowed Read Address
The I2C engine releases both SDA and SCL if the I2C bus is held low for Bus Low Time. If the gas gauge were
holding the lines, releasing them frees the master to drive the lines. If an external condition is holding either of
the lines low, the I2C engine enters the low-power SLEEP mode.
7.4 Device Functional Modes
The BQ35100 device is intended for systems where the battery electronics are required to consume a very low
average current. To achieve this, the device is intended to be fully powered off when not required through control
of the GAUGE ENABLE (GE) pin. When this pin is low, then the device is fully powered down with no
measurements being made and no data, unless in flash, is retained.
System Current
An example system current profile is shown along with the state of GAUGE ENABLE to reduce the average
power consumption of the battery electronics.
GE HIGH
0
GE LOW
Figure 10. Power Consumption
The average power consumption of the BQ35100 device is an average of the periods where GAUGE ENABLE is
high AND low over a given period.
For example, if the system enters a high power state (500 µA) for 30 s every 4 hours, the average current will be:
315 µA × 30 s / 4 h = 0.66 µA
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Device Functional Modes (continued)
When GAUGE ENABLE is low (GE = Low), then the device is powered off and the current is nominally
ICC_GELOW, and is the leakage current into the REGIN pin. Other components connected to this node should also
be evaluated to determine the "System Off" current total.
When the device is used for gas gauging, it transitions through several power states based on the selection of
OperationCfgA[GMSEL].
Figure 11 highlights the operational flow and conditional decisions.
Systems to
begin monitoring
Startup Phase
Host sets GE High
Device powers up
GE = GAUGE ENABLE Pin
Take initial
measurements and
check for warnings
Set INITCOMP = 1
Waiting Phase
NO
Device OK to
power down
Zy Z^d Zd[ D
from Host
YES
Active
Phase
Update Discharge
Accumulation from
Coulomb Counter
NO
Is GMSEL = 10
Update Voltage and
Temperature
NO
Check for warnings
and update status
YES
Update Voltage and
Current with 128 x
8-ms conversions
Execute Lifetime
Checks
Zy Z^dKW[ D
from Host
Update
Temperature
YES
Execute End of
Service detection
algorithm and
update status
Update Lifetime DF
YES
Update Voltage
Is GMSEL = 10
NO
YES
Set G _DONE =1
NO
Are Lifetime
updates
enabled?
Write accumulated
data and status to
DF
YES
Are DF updates
enabled?
NO
Data Update
Phase
Figure 11. Operational Flow
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8 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.
8.1 Application Information
The BQ35100 device is a highly configurable device with many options. The major configuration choices
comprise the battery chemistry and control methods.
8.2 Typical Applications
Figure 12 is a simplified diagram of the main features of the BQ35100 device. Specific implementations detailing
the main configuration options are shown later in this section.
BAT+
REGIN
I2C CLK
10 k 10 k
I2C DATA
REG25
ALERT
100k
100
1 VIN
SDA 14
2 ALERT
SCL 13
3 NC
VEN 12
REG 25
10k NTC
4 BAT
GAUGE ENABLE
TS 11
0.1 µF
5 GE
REGIN
VSUPPLY 1 M
REG25
1 µF
SRN 10
6 REGIN
SRP 9
7 REG25
VSS 8
100
0.1 µF
0.1 µF
0.1
75 ppm
100
0.1 µF
1 µF
PACK–
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Figure 12. BQ35100 Single-Cell Simplified Implementation
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Typical Applications (continued)
8.2.1 Design Requirements
For design guidelines, refer to the BQ35100 EVM User's Guide (SLUUBH7).
8.2.2 Detailed Design Procedure
8.2.2.1 Preparation for Gauging
Before it is ready to gauge a lithium primary battery, a BQ35100 device-based circuit requires several steps, as
follows:
1. Provide power to the device via a supply to the BAT pin that is above VREGIN, 2.7 V.
2. Power up the device by pulling the GE pin to a supply above VIH(GE), 2.65 V.
3. Use BQStudio to calibrate the device. The device is calibrated when in ACC Mode (GMSEL = 0x0), which is
also the state the device is shipped from TI. The BQ35100 EVM User Guide details the BQStudio software
and Calibration Tab operation.
4. Use BQStudio to update the CHEM ID. The Chemistry Tab enables the selection and programming of the
appropriate CHEM ID for the cell being used.
5. Reset the device once the calibration and CHEM ID programming are complete. To do this, toggle the GE
pin Low and then back High or via the Reset command in BQStudio.
With these steps complete the next phase of configuration and use is determined by which Gauging Mode is
intended to be used.
8.2.2.2 Gauging Mode Selection
The BQ35100 device can be configured to support lithium manganese dioxide (Li-MnO2) or lithium thionyl
chloride (Li-SOCl2) cells, and can also be configured to support any chemistry through the ACCUMULATOR
mode. To select the GAUGING mode, set the GMSEL[1:0] bits in Operation Config A register.
Table 3. Chemistry
Chemistry Supported
Gauging Mode
Operation Config A [GMSEL]
All Chemistries
ACCUMULATOR
0x0
Lithium Manganese Dioxide (Li-MnO2)
STATE-OF-HEALTH
(Voltage Correlation)
0x1
Lithium Thionyl Chloride (Li-SOCl2)
END-OF-SERVICE
(Resistance Correlation)
0x2
NOTE
During operation in the field, the BQ35100 fuel gauge should be used in only one mode at
a time, and should not be switched between modes.
8.2.2.2.1 ACCUMULATOR Mode
The ACCUMULATOR mode (ACC) is chemistry-independent and accumulates the passed discharge of the
battery when the gauge is enabled, but also provides no gas gauging data, such as remaining state-of-health
(RSOC), full charge capacity (FCC), or end-of-service (EOS) indication. This is the default configuration as it is
also the required mode for the device when it is calibrated. Once calibration is completed, the device can be set
to the appropriate gauging mode or left in the default mode.
To configure the BQ35100 fuel gauge to use the ACCUMULATOR mode, the following data flash configuration
variables must be configured correctly. For more details, including information on Operation Config A [GMSEL],
see the BQ35100 Technical Reference Manual (SLUUBH1).
To
1.
2.
3.
18
use ACCUMULATOR mode, follow these steps:
Step 1: Set GE high to power up the BQ35100 gauge and wait for ALERT to go low due to INITCOMP = 1.
Step 2: Clear ALERT (read BatteryStatus()) and send GAUGE_START().
Step 3: Read AccumulatedCapacity() for the latest passed discharge data since GAUGE_START().
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4. Step 4: Send GAUGE_STOP() and wait for ALERT to go low due to G_DONE = 1.
5. Step 5: Read final AccumulatedCapacity() value.
6. Step 6: Set GE low to power down the BQ35100 device.
8.2.2.2.1.1 STATE-OF-HEALTH (Voltage Correlation) Mode
STATE-OF-HEALTH mode is typically used with lithium manganese dioxide (Li-MnO2) cells as the voltage vs.
state-of-health (SOH) profile has a defined slope to enable accuracy.
To configure the BQ35100 gauge to use the STATE-OF-HEALTH mode, the following data flash configuration
variables must be configured correctly. For more details, including information on Operation Config A [GMSEL],
see the BQ35100 Technical Reference Manual (SLUUBH1).
To
1.
2.
3.
4.
5.
use STATE-OF-HEALTH mode, follow these steps:
Step 1: Set GE high to power up the BQ35100 gauge and wait for ALERT to go low due to INITCOMP = 1.
Step 2: Clear ALERT (read BatteryStatus()).
Step 3: Read any required data such as State-Of-Health() for the latest battery data.
Step 4: Optional: Send GAUGE_START().
Step 5: Optional: Send GAUGE_STOP(). At this point, Lifetime Data can be stored and any Threshold
detection checks are run. This is only needed if these features are desired.
6. Step 6: Set GE low to power down the BQ35100 device.
8.2.2.2.1.2 END-OF-SERVICE (Resistance Correlation) Mode
END-OF-SERVICE mode is only used with lithium thionyl chloride (Li-SOCl2) cells. To configure the BQ35100
device to use END-OF-SERVICE mode, the following data flash configuration variables must be configured
correctly. For more details, including information on Operation Config A [GMSEL], R Data Seconds, see the
BQ35100 Technical Reference Manual (SLUUBH1).
To
1.
2.
3.
4.
use END-OF-SERVICE mode, follow these steps:
Step 1: Set GE high to power up the BQ35100 device and wait for ALERT to go low due to INITCOMP = 1.
Step 2: Clear ALERT (read BatteryStatus()).
Step 3: Send GAUGE_START() 1 s prior to the high load pulse starting.
Step 4: Send GAUGE_STOP() directly after the high load pulse has stopped. During the time between Step4
and Step 5 there should be no other pulse load. A low current DC load is acceptable.
5. Step 5: Wait for ALERT to go low due to G_DONE = 1.
6. Step 6: Read BatteryStatus() for an [EOS] decision and other data, such as State-Of-Health().
7. Step 7: Set GE low to power down the BQ35100 device.
8.2.2.3 Voltage Measurement Selection
The default configuration is for the BQ35100 device to support 1-series cell with a maximum of 4.5 V. If the
battery voltage can be above this level, then [EXTVCELL] in Operation Config A should be set. In this setting,
an external resistor divider is used to scale the voltage so the gauge can measure accurately.
8.2.2.4 Temperature Measurement Selection
There are three options for temperature measurement in the BQ35100 device. By default, the device is
configured to use an external 103AT NTC thermistor. However, if [TEMPS] = 0, then an internal temperature
sensor is used. This requires no external components but for optimal performance in this case, the BQ35100
device should be very close to the cell, preferably thermally connected.
There is one other option that can be used if the system already includes a cell temperature measurement
solution: If WRTEMP = 1, then the host can write the temperature to the device and the BQ35100 algorithms will
use that data.
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8.2.2.5 Current Sense Resistor Selection
The BQ35100 device calculates current through measuring a voltage across a small resistor in series with the
battery. The default value is 100 mΩ. To maximize current measurement accuracy, the ideal value is calculated
as:
RSENSE (mΩ) = V(SR)Max / Peak Load Current (mA)
Where V(SR) MAX = 125 mV
8.2.2.6 Expected Device Usage Profiles
The BQ35100 device is designed to work in a system where there is a period discharge pulse of at least 10 s of
mA for 10 s of ms. In ACC mode, any pulse can be measured based on the information the host requires.
However, in EOS modes, the battery condition does not change very fast so only pulses that are many hours
apart; for example, 24 hours, are needed.
If the time between pulses needing monitoring is less than a minute, then it is recommended not to power down
the device. However, if the period is greater than 5 hours, then powering down the device between pulses is
expected. Periods in between risk not allowing the battery to rest and any EOS-related data may be
compromised. Battery EOS OCV BAD Warning provides more information on this.
The shorter the period between pulses has a large effect of the overall cumulative power consumption of the
battery electronics. See Device Functional Modes for more details on average power consumption.
8.2.2.7 Using the BQ35100 Fuel Gauge with a Battery and Capacitor in Parallel
The BQ35100 device can be used in systems where the lithium primary battery is permanently connected to a
bulk capacitor in parallel; for example, an electrolytic or super capacitor.
8.2.2.7.1 ACCUMULATOR Mode
In this mode, the BQ35100 device does not count the leakage of the capacitor, and so the leakage should be
added to the data the BQ35100 device counts.
8.2.2.7.2 STATE-OF-HEALTH Mode
In this mode, as the voltage of the capacitor will match that of the battery, there is no impact to the accuracy of
the device's gauging performance with the capacitor in the system.
8.2.2.7.3 END-OF-SERVICE Mode
In this mode, the resistance of the capacitor will influence the end-of-service determination, but this does not
impact the accuracy as the overall power delivery to the system is determined by the total resistance of the
combined battery and capacitor. However, for the resistance to be updated to support the end-of-service feature,
there needs to be a large enough delta in voltage between the open circuit voltage and the voltage under load.
As the battery is discharged, the resistance increases and so the resistance at a state of charge of < 50% is the
most important so that the accuracy will be optimized as the battery is in the second half of its service life.
The minimum delta voltage should be 100 mV to ensure there is no impact to the accuracy; therefore, the high
load pulse current when the gauge is active should be:
High Load Pulse Current (mA) = 100 mV / Resistance of the battery and capacitor in parallel at 50% SOC.
8.2.3 EOS Mode Load Pulse Synchronization
For correct data updates in EOS mode, the device operation needs to be synchronized with the pulsed load on
the battery. Typically, this is managed by the system host MCU, but additionally it can be managed by an
external detection circuit. An example of this alternative approach is detailed in TI Designs: TIDA-01546: Battery
and System Health Monitoring of Battery Powered Smart Flow Meters Reference Design (TIDUDO5).
8.2.4 Benefits of the BQ35100 Gauge Compared to Alternative Monitoring Techniques
The BQ35100 gauge offers many capabilities and provides a level of accuracy that alternative monitoring
techniques cannot offer. One of the main techniques is to use a voltage lookup table implemented with an MCU
and integrated ADC.
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Table 4. BQ35100 Compared to MCU + ADC
Operation
Advantages
Characterize the
cells' performance
under the expected
load condition to
create a voltage
versus SOH table
to measure voltage
and temperature
and compare the
measurements to
the characterized
table.
•
•
•
•
•
Disadvantages
•
Easy to implement
•
Accounts for early cell degradation
Most system host microcontrollers •
have a spare ADC channel.
Only uses a small amount of memory •
and CPU operation.
The table can be updated if the
system load configuration is changed
(for example, FW Update).
No simple accounting for cell-to-cell or temperature variation
No simple accounting for installation variations, such as radio power
due to transmit distances
Assumptions and tolerances must be built into the original cell
capacity, forcing a much larger, more expensive cell to be used.
Cell voltage is very flat so a small voltage measurement error is a very
large capacity error.
– LiSoCl2: 95% of SOC is 100 mV of voltage.
– A typical MCU ADC of 10-bit resolution has only seven bits of
accurate performance, providing a 36-mV resolution.
In summary, the voltage measurement performance of the measurement system is critical to this technique and
that is typically not available from the host MCU.
8.2.5 Application Curves
15
25
20
10
Current Error (mA)
Voltage Error (mV)
15
5
0
-5
-10
10
5
0
-5
-10
-15
-15
-20
2800
-40qC
-20qC
3000
3200
25qC
65qC
85qC
-40qC
-20qC
-20
3400 3600 3800
Battery Voltage (mV)
4000
4200
4400
-25
-3000
-2000
25qC
65qC
-1000
D001
Figure 13. V(Err) Across VIN (0 mA)
85qC
0
1000
Current (mA)
2000
3000
D003
Figure 14. I(Err)
2
1
Temperature Error (qC)
0
-1
-2
-3
-4
-5
-6
-7
-8
-9
-40
-20
0
20
40
Temperature (qC)
60
80
100
D004
Figure 15. T(Err)
9 Power Supply Recommendations
Power supply requirements for the BQ35100 device are simplified due to the presence of the internal LDO
voltage regulation. The REGIN pin accepts any voltage level between 2.7 V and 4.5 V, which is optimum for
single-cell Li-primary applications.
Decoupling the REGIN pin should be done with a 0.1-μF 10% ceramic X5R capacitor placed close to the device.
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REGIN can be powered from an alternate power source, such as, for example, the boost converter output, as
long as it is not also connected to the BAT input. In this case, BAT should only remain connected to the top of
the cell.
10 Layout
10.1 Layout Guidelines
10.1.1 Introduction
Attention to layout is critical to the success of any battery management circuit board. The mixture of high-current
paths with an ultralow-current microcontroller creates the potential for design issues that are not always trivial to
solve. Some of the key areas of concern are described in the following sections, and can help to enable success.
10.1.2 Power Supply Decoupling Capacitor
Power supply decoupling from VREG25 to ground is important for optimal operation of the gas gauge. To keep the
loop area small, place this capacitor next to the IC and use the shortest possible traces. A large loop area
renders the capacitor useless and forms a small-loop antenna for noise pickup. Ideally, the traces on each side
of the capacitor should be the same length and run in the same direction to avoid differential noise during ESD. If
possible, place a via near the VSS pin to a ground plane layer.
10.1.3 Capacitors
Power supply decoupling for the gas gauge requires a pair of 0.1-μF ceramic capacitors for (PBAT) and (VREG25)
pins. These should be placed reasonably close to the IC without using long traces back to VSS. The LDO voltage
regulator, whether external or internal to the main IC, requires a 0.47-μF ceramic capacitor to be placed fairly
close to the regulation output pin. This capacitor is for amplifier loop stabilization and as an energy well for the
2.5-V supply.
10.1.4 Communication Line Protection Components
The 5.6-V Zener diodes used to protect the communication pins of the gas gauge from ESD should be located as
close as possible to the pack connector. The grounded end of these Zener diodes should be returned to the
Pack(–) node rather than to the low-current digital ground system. This way, ESD is diverted away from the
sensitive electronics as much as possible.
10.2 Layout Example
10.2.1 Ground System
The fuel gauge requires a low-current ground system separate from the high-current PACK(–) path. ESD ground
is defined along the high-current path from the Pack(–) terminal to the sense resistor. It is important that the lowcurrent ground systems only connect to the PACK(–) path at the sense resistor Kelvin pick-off point. It is
recommended to use an optional inner layer ground plane for the low-current ground system.
In Figure 16, the green is an example of using the low-current ground as a shield for the gas gauge circuit. Note
how it is kept separate from the high-current ground, which is shown in red. The high-current path is joined with
the low-current path only at one point, shown with the small blue connection between the two planes.
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Layout Example (continued)
Figure 16. Differential Filter Component with Symmetrical Layout
10.2.2 Kelvin Connections
Kelvin voltage sensing is very important to accurately measure current and cell voltage. Note how the differential
connections at the sense resistor do not add any voltage drop across the copper etch that carries the high
current path through the sense resistor. See Figure 16 and Figure 17.
10.2.3 Board Offset Considerations
Although the most important component for board offset reduction is the decoupling capacitor for VREG25, an
additional benefit is possible by using this recommended pattern for the coulomb counter differential low-pass
filter network. Maintain the symmetrical placement pattern shown for optimum current offset performance. Use
symmetrical shielded differential traces, if possible, from the sense resistor to the 100-Ω resistors, as shown in
Figure 17.
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Layout Example (continued)
Figure 17. Differential Connection Between SRP and SRN Pins with Sense Resistor
10.3 ESD Spark Gap
Protect the communication lines from ESD with a spark gap at the connector. Figure 18 shows the recommended
pattern with its 0.2-mm spacing between the points.
Figure 18. Recommended Spark-Gap Pattern Helps Protect Communication Lines from ESD
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11 Device and Documentation Support
11.1 Documentation Support
11.1.1 Related Documentation
For related documentation, see the following:
• BQ35100 Technical Reference Manual (SLUUBH1)
• BQ35100 EVM User's Guide (SLUUBH7)
• Using I2C Communication with the BQ275xx Series of Fuel Gauges Application Report (SLUA467)
11.2 Receiving Notification of Documentation Updates
To receive notification of documentation updates, navigate to the device product folder on ti.com. In the upper
right corner, click on Alert me to register and receive a weekly digest of any product information that has
changed. For change details, review the revision history included in any revised document.
11.3 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.
11.4 Trademarks
E2E is a trademark of Texas Instruments.
All other trademarks are the property of their respective owners.
11.5 Electrostatic Discharge Caution
This integrated circuit can be damaged by ESD. Texas Instruments recommends that all integrated circuits be handled with
appropriate precautions. Failure to observe proper handling and installation procedures can cause damage.
ESD damage can range from subtle performance degradation to complete device failure. Precision integrated circuits may be more
susceptible to damage because very small parametric changes could cause the device not to meet its published specifications.
11.6 Glossary
SLYZ022 — TI Glossary.
This glossary lists and explains terms, acronyms, and definitions.
12 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
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PACKAGING INFORMATION
Orderable Device
Status
(1)
Package Type Package Pins Package
Drawing
Qty
Eco Plan
Lead/Ball Finish
MSL Peak Temp
(2)
(6)
(3)
Op Temp (°C)
Device Marking
(4/5)
BQ35100PW
ACTIVE
TSSOP
PW
14
90
Green (RoHS
& no Sb/Br)
CU NIPDAU
Level-2-260C-1 YEAR
-40 to 85
BQ35100
BQ35100PWR
ACTIVE
TSSOP
PW
14
2000
Green (RoHS
& no Sb/Br)
CU NIPDAU
Level-2-260C-1 YEAR
-40 to 85
BQ35100
(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 <=1000ppm threshold. Antimony trioxide based
flame retardants must also meet the <=1000ppm threshold requirement.
(3)
MSL, Peak Temp. - The Moisture Sensitivity Level rating according to the JEDEC industry standard classifications, and peak solder temperature.
(4)
There may be additional marking, which relates to the logo, the lot trace code information, or the environmental category on the device.
(5)
Multiple Device Markings will be inside parentheses. Only one Device Marking contained in parentheses and separated by a "~" will appear on a device. If a line is indented then it is a continuation
of the previous line and the two combined represent the entire Device Marking for that device.
(6)
Lead/Ball Finish - Orderable Devices may have multiple material finish options. Finish options are separated by a vertical ruled line. Lead/Ball Finish values may wrap to two lines if the finish
value exceeds the maximum column width.
Important Information and Disclaimer:The information provided on this page represents TI's knowledge and belief as of the date that it is provided. TI bases its knowledge and belief on information
provided by third parties, and makes no representation or warranty as to the accuracy of such information. Efforts are underway to better integrate information from third parties. TI has taken and
continues to take reasonable steps to provide representative and accurate information but may not have conducted destructive testing or chemical analysis on incoming materials and chemicals.
TI and TI suppliers consider certain information to be proprietary, and thus CAS numbers and other limited information may not be available for release.
In no event shall TI's liability arising out of such information exceed the total purchase price of the TI part(s) at issue in this document sold by TI to Customer on an annual basis.
Addendum-Page 1
Samples
PACKAGE OPTION ADDENDUM
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8-Apr-2019
Addendum-Page 2
PACKAGE MATERIALS INFORMATION
www.ti.com
13-Nov-2019
TAPE AND REEL INFORMATION
*All dimensions are nominal
Device
BQ35100PWR
Package Package Pins
Type Drawing
TSSOP
PW
14
SPQ
Reel
Reel
A0
Diameter Width (mm)
(mm) W1 (mm)
2000
330.0
12.4
Pack Materials-Page 1
6.9
B0
(mm)
K0
(mm)
P1
(mm)
5.6
1.6
8.0
W
Pin1
(mm) Quadrant
12.0
Q1
PACKAGE MATERIALS INFORMATION
www.ti.com
13-Nov-2019
*All dimensions are nominal
Device
Package Type
Package Drawing
Pins
SPQ
Length (mm)
Width (mm)
Height (mm)
BQ35100PWR
TSSOP
PW
14
2000
367.0
367.0
38.0
Pack Materials-Page 2
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