MAX17047/MAX17050
ModelGauge m3 Fuel Gauge
Simplified Operating Circuit
19-6008; Rev 3; 8/12
Ordering Information appears at end of data sheet.
For related parts and recommended products to use with this part,
refer to: www.maximintegrated.com/MAX17047.related
ModelGauge is a trademark of Maxim Integrated Products, Inc.
General Description
The MAX17047/MAX17050 incorporate the Maxim
ModelGauge™ m3 algorithm that combines the excellent
short-term accuracy and linearity of a coulomb counter
with the excellent long-term stability of a voltage-based fuel
gauge, along with temperature compensation to provide
industry-leading fuel-gauge accuracy. ModelGauge m3
cancels offset accumulation error in the coulomb counter,
while providing better short-term accuracy than any purely
voltage-based fuel gauge. Additionally, the ModelGauge
m3 algorithm does not suffer from abrupt corrections that
normally occur in coulomb-counter algorithms, since tiny
continual corrections are distributed over time.
The device automatically compensates for aging, tem-
perature, and discharge rate and provides accurate state
of charge (SOC) in mAh or %, as well as time-to-empty
over a wide range of operating conditions. The device
provides two methods for reporting the age of the bat-
tery: reduction in capacity and cycle odometer.
The device provides precision measurements of current,
voltage, and temperature. Temperature of the battery
pack is measured using an external thermistor supported
by ratiometric measurements on an auxiliary input. A
2-wire (I2C) interface provides access to data and control
registers. The MAX17047 is available in a lead(Pb)-free,
3mm x 3mm, 10-pin TDFN package. The MAX17050 is
available in a 0.4mm pitch 9-bump WLP package.
Applications
Features
S Accurate Battery-Capacity and Time-To-Empty
Estimation
Temperature, Age, and Rate Compensated
Does Not Require Empty, Full, or Idle States to
Maintain Accuracy
S Precision Measurement System
No Calibration Required
S ModelGauge m3 Algorithm
Long-Term Influence by Voltage Fuel Gauge
Cancels Coulomb-Counter Drift
Short-Term Influence by Coulomb Counter
Provides Excellent Linearity
Adapts to Cell Characteristics
S External Temperature-Measurement Network
Actively Switched Thermistor Resistive Divider
Reduces Current Consumption
S Low Quiescent Current
25µA Active, < 0.5µA Shutdown
S Alert Indicator for SOC, Voltage, Temperature, and
Battery Removal/Insertion Events
S AtRate Estimation of Remaining Capacity
S 2-Wire (I2C) Interface
S Tiny, Lead(Pb)-Free, 3mm x 3mm, 10-Pin TDFN
Package or Tiny 0.4mm Pitch 9-Bump WLP Package
2.5G/3G/4G Wireless
Handsets
Smartphones/PDAs
Tablets and Handheld
Computers
Portable Game Players
e-Readers
Digital Still and Video
Cameras
Portable Medical Equipment
0.1µF0.1µF
OPTIONAL
10nF
OPTIONAL
10kI
PK-
PK+
T
OPTIONAL
10kI
NTC
THERMISTOR 10mI
RSNS
CSP
REG
AIN SCL
THRM
VBATT
VTT
(MAX17047 ONLY)
CSNEP
SDA
ALRT
MAX17047
MAX17050
PROTECTION
SYSTEM
BATTERY PACK
HOST
µP
For pricing, delivery, and ordering information, please contact Maxim Direct
at 1-888-629-4642, or visit Maxim’s website at www.maximintegrated.com.
2Maxim Integrated
MAX17047/MAX17050
ModelGauge m3 Fuel Gauge
VBATT, SDA, SCL, ALRT to CSP .............................-0.3V to +6V
REG to CSP ..........................................................-0.3V to +2.2V
VTT to CSP ...............................................................-0.3V to +6V
THRM, AIN to CSP .....................................-0.3V to (VTT + 0.3V)
CSN to CSP ................................................................-2V to +2V
Continuous Sink Current (VTT) ...........................................20mA
Continuous Sink Current (SCL, SDA, ALRT) ......................20mA
Continuous Power Dissipation (TA = +70NC)
TDFN (derate 24.4mW/NC above +70NC) .............. .1951.2mW
WLP (derate 11.9mW/NC above +70NC)...................952.0mW
Operating Temperature Range .......................... -40NC to +85NC
Junction Temperature .....................................................+150NC
Storage Temperature Range ............................ -55NC to +125NC
Lead Temperature (soldering 10s) .................................+300NC
Soldering Temperature (reflow) ......................................+260NC
ABSOLUTE MAXIMUM RATINGS
ELECTRICAL CHARACTERISTICS
(VBATT = 2.5V to 4.5V, TA = -20NC to +70NC, unless otherwise noted. Typical values are at TA = +25NC.) (Note 2)
TDFN
Junction-to-Ambient Thermal Resistance (qJA) ..........41°C/W
Junction-to-Case Thermal Resistance (qJC) .................9°C/W
WLP
Junction-to-Ambient Thermal Resistance (qJA) ..........84°C/W
Note 1: Package thermal resistances were obtained using the method described in JEDEC specification JESD51-7, using a four-layer
board. For detailed information on package thermal considerations, refer to www.maximintegrated.com/thermal-tutorial.
PACKAGE THERMAL CHARACTERISTICS (Note 1)
Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional opera-
tion of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute
maximum rating conditions for extended periods may affect device reliability.
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
Supply Voltage VBATT (Note 3) 2.5 4.5 V
Supply Current IDD0 Shutdown mode, TA P +50NC0.5 2 FA
IDD1 Active mode, average current 25 42
REG Regulation Voltage VREG 1.5 1.9 V
Measurement Error, VBATT VGERR
TA = +25NC-7.5 +7.5 mV
-20 +20
Measurement Resolution, VBATT VLSb 0.625 mV
VBATT Measurement Range VFS 2.5 4.98 V
Input Resistance CSN, AIN 15 MI
Ratiometric Measurement
Accuracy, AIN TGERR -0.5 +0.5 %
Ratiometric Measurement
Resolution, AIN TLSb 0.0244 % Full
Scale
Current Register Resolution ILSb 1.5625 FV
Current Full-Scale Magnitude IFS Q51.2 mV
Current Offset Error IOERR Q1.5 FV
Current Gain Error IGERR -1 +1 % of
Reading
Time-Base Accuracy tERR
VDD = 3.6V at TA = +25NC-1 +1
%
TA = 0NC to +50NC-2.5 +2.5
TA = -20NC to +70NC-3.5 +3.5
3Maxim Integrated
MAX17047/MAX17050
ModelGauge m3 Fuel Gauge
ELECTRICAL CHARACTERISTICS (continued)
(VBATT = 2.5V to 4.5V, TA = -20NC to +70NC, unless otherwise noted. Typical values are at TA = +25NC.) (Note 2)
ELECTRICAL CHARACTERISTICS (2-WIRE INTERFACE)
(2.5V P VBATT P 4.5V, TA = -20NC to +70NC.) (Note 2)
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
THRM Output Drive IOUT = 0.5mA VTT - 0.1 V
THRM Precharge Time tPRE 8.48 ms
SDA, SCL, ALRT
Input Logic High VIH 1.5 V
SDA, SCL, ALRT Input Logic Low VIL 0.5 V
SDA, ALRT Output Logic Low VOL IOL = 4mA 0.4 V
SDA, ALRT Pulldown Current IPD Active mode, VSDA = 0.4V, VALRT = 0.4V 0.05 0.2 0.4 FA
ALRT Leakage 1FA
THRM Operating Range 2.5 VTT V
Battery-Removal Detection
Threshold—VAIN Rising VDETR VTHRM - VAIN 40 125 200 mV
Battery-Removal Detection
Threshold—VAIN Falling VDETF VTHRM - VAIN 70 150 230 mV
Battery-Removal Detection
Comparator Delay tTOFF
VAIN step from 70% to 100% of VTHRM to
ALRT falling; Alrtp = logic 0;
EnAIN = logic 1; FTHRM = logic 1
100 Fs
External AIN Capacitance RTHM = 10kI NTC 100 nF
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
SCL Clock Frequency fSCL (Note 4) 0 400 kHz
Bus Free Time Between a STOP
and START Condition tBUF 1.3 Fs
Hold Time (Repeated)
START Condition tHD:STA (Note 5) 0.6 Fs
Low Period of SCL Clock tLOW 1.3 Fs
High Period of SCL Clock tHIGH 0.6 Fs
Setup Time for a Repeated
START Condition tSU:STA 0.6 Fs
Data Hold Time tHD:DAT (Notes 6, 7) 0 0.9 Fs
Data Setup Time tSU:DAT (Note 6) 100 ns
Rise Time of Both SDA and SCL
Signals tR20 +
0.1CB300 ns
4Maxim Integrated
MAX17047/MAX17050
ModelGauge m3 Fuel Gauge
I2C Bus Timing Diagram
Figure 1. I2C Bus Timing Diagram
Note 2: Specifications are 100% tested at TA = +25°C. Limits over the operating range are guaranteed by design and
characterization.
Note 3: All voltages are referenced to CSP.
Note 4: Timing must be fast enough to prevent the device from entering shutdown mode due to bus low for a period > 45s minimum.
Note 5: fSCL must meet the minimum clock low time plus the rise/fall times.
Note 6: The maximum tHD:DAT has only to be met if the device does not stretch the low period (tLOW) of the SCL signal.
Note 7: This device internally provides a hold time of at least 100ns for the SDA signal (referred to the minimum VIH of the SCL
signal) to bridge the undefined region of the falling edge of SCL.
Note 8: Filters on SDA and SCL suppress noise spikes at the input buffers and delay the sampling instant.
Note 9: CB—total capacitance of one bus line in pF.
ELECTRICAL CHARACTERISTICS (2-WIRE INTERFACE) (continued)
(2.5V P VBATT P 4.5V, TA = -20NC to +70NC.) (Note 2)
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
Fall Time of Both SDA and SCL
Signals tF20 +
0.1CB300 ns
Setup Time for STOP Condition tSU:STO 0.6 Fs
Spike Pulse Widths
Suppressed by Input Filter tSP (Note 8) 0 50 ns
Capacitive Load for Each Bus
Line CB(Note 9) 400 pF
SCL, SDA Input Capacitance CBIN 60 pF
SDA
SCL
tF
tLOW
tHD:STA tHD:DAT
tSU:STA tSU:STO
tSU:DAT tHD:STA
tSP tRtBUF
tR
tF
SSrPS
5Maxim Integrated
MAX17047/MAX17050
ModelGauge m3 Fuel Gauge
Typical Operating Characteristics
(TA = +25°C, unless otherwise noted.)
SHUTDOWN CURRENT
vs. SUPPLY VOLTAGE
MAX17047 toc01
VBATT (V)
SHUTDOWN CURRENT (uA)
541 2 3
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0
0
TA = +70°C
TA = +25°C
TA = -20°C
ACTIVE CURRENT vs. SUPPLY VOLTAGE
MAX17047 toc02
VBATT (V)
ACTIVE CURRENT (uA)
54321
5
10
15
20
25
30
35
0
0
TA = +25°C
TA = +70°C
TA = -20°C
VOLTAGE ADC ERROR vs. TEMPERATURE
AND SUPPLY VOLTAGE
MAX17047 toc03
VBATT (V)
VOLTAGE ADC ERROR (mV)
4.23.73.22.7
-8
-6
-4
-2
0
2
4
6
8
10
-10
2.2
TA = -20°C
TA = +70°C
TA = +25°C
CURRENT ADC ERROR
vs. TEMPERATURE
MAX17047 toc04
CURRENT FORCED (A)
CURRENT ADC ERROR (mA)
10-1
-10
-50
0
5
10
15
-15
-2 2
TA = +25°C TA = +70°C
TA = -20°C
RESPONSE TO TEMPERATURE TRANSIENT
AT CONSTANT-CURRENT LOAD
MAX17047 toc06
TIME (Hr)
SOC (%), TEMPERATURE (°C)
321
10
20
30
40
50
60
70
80
90
100
0
VCELL (V)
2.6
2.8
3.0
3.2
3.4
3.6
3.8
4.0
4.2
4.4
2.4
0
VCELL RISES WITH
TEMPERATURE DURING
CONSTANT LOAD
FUEL GAUGE CHANGES
TRAJECTORY AFTER
TEMPERATURE CHANGE
EMPTY VOLTAGE
SOCREP
SOCAV
TEMPERATURE
AUXILIARY INPUT ADC ERROR
vs. TEMPERATURE
MAX17047 toc05
AIN RATIO TO VTT (%)
AUXILIARY INPUT ADC ERROR (%)
908060 7020 30 40 5010
-0.8
-0.6
-0.4
-0.2
0
0.2
0.4
0.6
0.8
1.0
-1.0
0 100
TA = +25°C
TA = -20°C
TA = +70°C
END OF CHARGE DETECTION
MAX17047 toc07
TIME (Hr)
CAPACITY (mAh); CURRENT (mA)
642
-1
0
1
2
3
4
5
6
7
8
-2
08
FULLCAP
VCELL (V)
2.9
3.1
3.3
3.5
3.7
3.9
4.1
4.3
4.5
4.7
2.7
VALID END-OF-CHARGE
DETECTION EVENT
REMCAPREP
VCELL
NEAR-FULL FALSE
CHARGE TERMINATION
EVENTS REJECTED
CURRENT
6Maxim Integrated
MAX17047/MAX17050
ModelGauge m3 Fuel Gauge
Typical Operating Characteristics (continued)
(TA = +25°C, unless otherwise noted.)
COLD DISCHARGE (0°C)
MAX17047 toc08
TIME (Hr)
STATE OF CHARGE (%)
8642
10
20
30
40
50
60
70
80
90
100
0
01
0
ERROR (%)
-8
-6
-4
-2
0
2
4
6
8
10
-10
REFERENCE
SOC
SOCREP
ERROR
CHARGE AND DISCHARGE AT +20°C
TIME (Hr)
STATE OF CHARGE (%)
ERROR (%)
105
10
20
30
40
50
60
70
80
90
100
0
-8
-6
-4
-2
0
2
4
6
8
10
-10
01
5
ERROR
MAX17047 toc10
C/2 DISCHARGE
SOCREP
REFERENCE
SOC
C/4 DISCHARGE
C/7 DISCHARGE
C/9 DISCHARGE
DISCHARGE AT +40°C
MAX17047 toc09
TIME (Hr)
STATE OF CHARGE (%)
8642
10
20
30
40
50
60
70
80
90
100
0
01
0
ERROR (%)
-8
-6
-4
-2
0
2
4
6
8
10
-10
C/4 DISCHARGE
C/7 DISCHARGE
C/9 DISCHARGE
REFERENCE
SOC
SOCREP
ERROR
CHARGE AND DISCHARGE IN
ACTUAL SYSTEM
TIME (Hr)
STATE OF CHARGE (%) OR TEMPERATURE (°C)
VCELL (V)
105
10
20
30
40
50
60
70
80
90
100
0
3.3
3.4
3.5
3.6
3.7
3.8
3.9
4.0
4.1
4.2
3.2
0
VCELL
REFERENCE SOC (%)
MAX17047 toc11
SOCREP (%)
TEMPERATURE
7Maxim Integrated
MAX17047/MAX17050
ModelGauge m3 Fuel Gauge
Pin/Bump Descriptions
Pin/Bump Configurations
PIN BUMP NAME FUNCTION
TDFN WLP
1 — VTT
Supply Input for Thermistor Bias Switch (MAX17047 Only.) VTT is connected internally to VBATT
on the MAX17050. Connect to supply for ratiometric AIN pin-voltage measurements. In most
applications, connect VTT to VBATT.
2 A1 AIN Auxiliary Voltage Input. Auxiliary voltage input from external thermal-measurement network. AIN
also provides battery insertion/removal detection. Connect to VBATT, if not used.
3 A2 SCL Serial Clock Input. 2-wire clock line. Input only.
4 C1 SDA Serial Data Input/Out. 2-wire data line. Open-drain output driver.
5 A3 CSN Sense Resistor Connection. System ground connection and sense resistor input.
6 C3 CSP Chip Ground and Sense Resistor Input
7 B3 REG Voltage Regulator Bypass. Connect a 0.1FF capacitor from REG to CSP.
8 B2 ALRT
Alert Indication. An open-drain n-channel output used to indicate specified condition thresholds
have been met. A 200kI pullup resistor to power rail is required for use as an output. Alternatively,
ALRT can operate as a shutdown input with the output function disabled.
9 C2 THRM Thermistor Bias Connection. Supply for thermistor resistor-divider. Connect to the high side of the
thermistor/resistor-divider. THRM connects internally to VTT during temperature measurement.
10 B1 VBATT Power-Supply and Battery Voltage-Sense Input. Kelvin connect to positive terminal of battery pack.
Bypass with a 0.1FF capacitor to CSP.
— — EP Exposed Pad (TDFN Only). Connect to CSP.
1
3
4
10
8
7
VBATT
ALRT
REG
VTT
SCL
SDA
MAX17047
29
THRMAIN
56
CSPCSN
TDFN
TOP VIEW
+
EP
WLP
MAX17050
+
AIN
1
A
B
C
23
VBATT
SDA THRM CSP
ALRT REG
CSNSCL
8Maxim Integrated
MAX17047/MAX17050
ModelGauge m3 Fuel Gauge
Block Diagram
Detailed Description
The MAX17047/MAX17050 incorporate the Maxim
ModelGauge m3 algorithm that combines the excellent
short-term accuracy and linearity of a coulomb counter
with the excellent long-term stability of a voltage-based
fuel gauge, along with temperature compensation to pro-
vide industry-leading fuel-gauge accuracy. ModelGauge
m3 cancels offset accumulation error in the coulomb
counter, while providing better short-term accuracy than
any purely voltage-based fuel gauge. Additionally, the
ModelGauge m3 algorithm does not suffer from abrupt
corrections that normally occur in coulomb-counter algo-
rithms, since tiny continual corrections are distributed
over time.
The device automatically compensates for aging, tem-
perature, and discharge rate and provides accurate
state-of-charge (SOC) in mAh or % over a wide range of
operating conditions. The device provides two methods
for reporting the age of the battery: reduction in capacity
and cycle odometer.
The device provides precision measurements of current,
voltage, and temperature. Temperature of the battery
pack is measured using an external thermistor supported
by ratiometric measurements on an auxiliary input. A
2-wire (I2C) interface provides access to data and control
registers. The MAX17047 is available in a 3mm x 3mm,
10-pin TDFN package. The MAX17050 is available in a
0.4mm pitch 9-bump WLP package.
ModelGauge m3 Algorithm
The ModelGauge m3 algorithm combines a high-accura-
cy coulomb counter with a voltage fuel gauge (VFG) as
represented in Figure 2.
Classical coulomb-counter-based fuel gauges have
excellent linearity and short-term performance. However,
they suffer from drift due to the accumulation of the offset
error in the current-sense measurement. Although the
offset error is often very small, it cannot be eliminated,
causes the reported capacity error to increase over
time, and requires periodic corrections. Corrections are
usually performed at full or empty. Some other systems
also use the relaxed battery voltage to perform correc-
tions. These systems determine the SOC based on the
battery voltage after a long time of no current flow. Both
have the same limitation: if the correction condition is not
0.1µF
PK-
PK-
CSP
PK- PK- SYSTEM GROUND
PK+
PK+
10nF
0.1µF
10mI
RSNS
32kHz OSCILLATOR
OCV CALCULATION
ModelGauge m3
ALGORITHM
2V LDO
VBATT
VBATT
REG
P
SDA
ALRT
SCL
VTT
(MAX17047 ONLY)
THRM
VTHRM - VDETR/VDETF
BATTERY
REMOVAL
REF
DETECT
CSP CSN
AIN
IN
OUT
MUX 12-BIT ADC I2C
INTERFACE
REF ADC
MAX17047
MAX17050
9Maxim Integrated
MAX17047/MAX17050
ModelGauge m3 Fuel Gauge
observed over time in the actual application, the error in
the system is boundless. The performance of classic
coulomb counters is dominated by the accuracy of such
corrections.
Classical voltage-measurement-based SOC estimation
has poor accuracy due to inadequate cell modeling, but
does not accumulate offset error over time.
The device includes an advanced VFG, which estimates
open-circuit voltage (OCV), even during current flow, and
simulates the nonlinear internal dynamics of a lithium-ion
(Li+) battery to determine the SOC with improved accu-
racy. The model considers the time effects of a battery
caused by the chemical reactions and impedance in the
battery to determine SOC based on table lookup. This
SOC estimation does not accumulate offset error over time.
The ModelGauge m3 algorithm combines a high-accu-
racy coulomb counter with a VFG. The complementary
combined result eliminates the weaknesses of both the
coulomb counter and the VFG, while providing the
strengths of both. A mixing algorithm combines the VFG
capacity with the coulomb counter and weighs each
result so that both are used optimally to determine the
battery state. In this way, the VFG capacity result is used
to continuously make small adjustments to the battery
state, canceling the coulomb-counter drift.
The ModelGauge m3 algorithm uses this battery state
information and accounts for temperature, battery cur-
rent, age, and application parameters to determine the
remaining capacity available to the system.
The ModelGauge m3 algorithm continually adapts to the
cell and application through independent learning rou-
tines. As the cell ages, its change in capacity is monitored
and updated and the VFG dynamics adapt based on cell-
voltage behavior in the application.
Figure 2. ModelGauge m3 Overview
EMPTY
DETECTION
CURRENT
TIME
RELAXED
CELL
DETECTION
CAPACITY LEARN
mAh PER %
VOLTAGE FUEL GAUGE
CURRENT
TEMPERATURE
COULOMB COUNTER
mAh OUTPUT
MIXING ALGORITHM
mAh OUTPUT
RemCapMIX
SOCMIX
APPLICATION
EMPTY
COMPENSATION
END-OF-CHARGE
DETECTION
APPLICATION
OUTPUTS: CELL CHEMISTRY
OUTPUTS:
SOCREP
RemCapREP
SOCAV
RemCapAV
TTE
FullCAP
OCV
CYCLES
RCELL
FullCAPNom
AGE
OCV TEMPERATURE-
COMPENSATION LEARN
VOLTAGE
OCV TABLE LOOKUP
% REMAINING OUTPUT
OCV CALCULATION
OCV OUTPUT
10Maxim Integrated
MAX17047/MAX17050
ModelGauge m3 Fuel Gauge
Figure 4. ModelGauge m3 Algorithm Mixing Conceptual Illustration
OCV Estimation and Coulomb-Count Mixing
The core of the ModelGauge m3 algorithm is a mixing
algorithm that combines the OCV state estimation with
the coulomb counter. After power-on reset of the IC,
coulomb-count accuracy is unknown. The OCV state
estimation is weighted heavily compared to the coulomb-
count output. As the cell progresses through cycles in
the application, coulomb-counter accuracy improves
and the mixing algorithm alters the weighting so that
the coulomb-counter result is dominant. From this point
forward, the IC switches to servo mixing. Servo mixing
provides a fixed magnitude continuous error correction to
the coulomb count, up or down, based on the direction
of error from the OCV estimation. This allows differences
between the coulomb count and OCV estimation to be
corrected quickly. See Figure 3.
The resulting output from the mixing algorithm does
not suffer drift from current measurement offset error
and is more stable than a stand-alone OCV estimation
algorithm; see Figure 4. Initial accuracy depends on the
relaxation state of the cell. The highest initial accuracy is
achieved with a fully relaxed cell.
Fuel-Gauge Empty Compensation
As the temperature and discharge rate of an applica-
tion changes, the amount of charge available to the
applica tion also changes. The ModelGauge m3 algo-
rithm dis tinguishes between remaining capacity of the
cell (RemCapMIX) and remaining capacity of the appli-
cation (RemCapAV) and reports both results to the user.
Fuel-Gauge Learning
The device periodically makes internal adjustments
to cell characterization and application information to
remove initial error and maintain accuracy as the cell
ages. These adjustments always occur as small under-
corrections to prevent instability of the system and
prevent any noticeable jumps in the fuel-gauge outputs.
Learning occurs automatically without any input from the
host. To maintain learned accuracy through power loss,
the host must periodically save learned information and
then restore after power is returned. See the Power-Up
and Power-On Reset section for details:
• Full Capacity Available to Application (FullCAP).
This is the total capacity available to the application
at full. FullCAP is updated near the end of charging
when termination is detected. See the End-of-Charge
Detection section.
Figure 3. ModelGauge m3 OCV and Coulomb-Count Mixing
CELL CYCLES
OCV AND COULOMB-COUNT
MIXING RATIO
1.501.000.500
0%
100%
2.00
COULOMB-COUNT INFLUENCE SERVO MIXING
OCV
INFLUENCE
TIME
STATE-OF-CHARGE ERROR
(SHADED AREA)
ModelGauge m3
OCV + COULOMB-COUNT MIXING
MAXIMUM ERROR RANGE
MAXIMUM COULOMB-COUNTER ERROR
TYPICAL OCV ESTIMATION
ERROR AS CELL IS CYCLED
11Maxim Integrated
MAX17047/MAX17050
ModelGauge m3 Fuel Gauge
• Cell Capacity (FullCapNom). This is the total cell
capacity at full, according to the VFG. This includes
some capacity that is not available to the application
at high loads and/or low temperature. The device
periodically compares percent change based on OCV
measurement vs. coulomb-count change as the cell
charges and discharges. This information allows the
device to maintain an accurate estimation of the cell’s
capacity in mAh as the cell ages.
• Voltage Fuel-Gauge Adaptation. The device
observes the battery’s relaxation response and
adjusts the dynamics of the VFG. This adaptation
adjusts the RCOMP0 register during qualified cell
relaxation events.
• Empty Compensation. The device updates inter-
nal data whenever cell empty is detected (VCELL <
V_empty) to account for cell age or other cell devia-
tions from the characterization information.
Determining Fuel-Gauge Accuracy
To determine the true accuracy of a fuel gauge, as expe-
rienced by end users, the battery should be exercised
in a dynamic manner. The end-user accuracy cannot be
understood with only simple cycles.
To challenge a correction-based fuel gauge, such as
a coulomb counter, test the battery with partial loading
sessions. For example, a typical user may operate the
device for 10min and then stop use for an hour or more.
A robust test method includes these kinds of sessions
many times at various loads, temperatures, and duration.
Refer to Application Note 4799: Cell Characterization
Procedure for a ModelGauge m3 Fuel Gauge.
Initial Accuracy
The device uses the first voltage reading after power-up
or after cell insertion to determine the starting output of
the fuel gauge. It is assumed that the cell is fully relaxed
prior to this reading; however, this is not always the
case. If the cell was recently charged or discharged, the
voltage measured by the device may not represent the
true state of charge of the cell, resulting in initial error in
the fuel gauge outputs. In most cases, this error is minor
and is quickly removed by the fuel gauge algorithm dur-
ing normal operation.
Typical Operating Circuit
The device is designed to mount outside the cell pack
that it monitors. Voltage of the battery pack is measured
directly at the pack terminals by the VBATT and CSP
connections. Current is measured by an external sense
resistor placed between the CSP and CSN pins. An
external resistor-divider network allows the device to
measure temperature of the cell pack by monitoring the
AIN pin. The THRM pin provides a strong pullup for the
resistor-divider that is internally disabled when tempera-
ture is not being measured.
Communication to the host occurs over a standard I2C
interface. SCL is an input from the host, and SDA is an
open-drain I/O pin that requires an external pullup. The
ALRT pin is an output that can be used as an external
interrupt to the host processor if certain application con-
ditions are detected. ALRT can also function as an input,
allowing the host to shut down the device. This pin is
also open drain and requires an external pullup resistor.
Figure 5 is the typical operating circuit.
Multicell Circuit
The MAX17047 can be used in multicell pack applica-
tions. A resistor-divider network divides the pack voltage
down so that the IC monitors the equivalent voltage of a
single cell. The MAX9910 buffers the divider output so
that loading by the MAX17047 does not affect accuracy.
VTT must be connected to a regulated supply in the sys-
tem to prevent overloading the MAX9910. Contact the
factory for a MAX17050 multicell application circuit. See
Figure 6.
Thermistor Sharing Circuit
The MAX17047 can share the cell thermistor circuit
with the system charger. In this circuit, there is a single
thermistor inside the cell pack and a single bias resistor
external to the cell pack. The device shares the same
external bias as the charger circuit and measurement
point on the thermistor. In this configuration, each device
can measure temperature individually or simultaneously
without interference. Alternatively, if the bias voltage in
the charger circuit is not available to the device, a sepa-
rate bias voltage on the VTT pin can be used. For proper
operation, the separate bias voltage must be larger than
the minimum operating voltage of the device, but no
larger than one diode drop above the charger circuit
bias voltage. The MAX17050 cannot be operated in his
configuration. See Figure 7.
12Maxim Integrated
MAX17047/MAX17050
ModelGauge m3 Fuel Gauge
Figure 5. Typical Operating Circuit
Figure 6. Multicell Application Circuit
0.1µF0.1µF
OPTIONAL
10nF
OPTIONAL
10kI
PK-
PK+
T
OPTIONAL
10kI
NTC
THERMISTOR 10mI
RSNS
CSP
REG
AIN SCL
THRM
VBATT
VTT
(MAX17047 ONLY)
CSNEP
SDA
ALRT
MAX17047
MAX17050
OPTIONAL
200kI
OPTIONAL
5kI
SYSTEM
BATTERY PACK
HOST
µP
PROTECTION IC
THERMISTOR
MEASUREMENT OPTIONAL
MAX17047
3.3nF
4.5V-5.5V
REGULATOR
SYSTEM
MAX9910
0.1µF
OPTIONAL
10kI
OPTIONAL
200kI
SYSTEM
GROUND
10mI
OPTIONAL
5kI
OPTIONAL
10nF
THRM
ALRT
VTT
AIN
VB CSP EP
0.1µF
VBATT
PK-
T
PK-
PK+
1mI
N-1
mI
PK-
100I
47kI
SDA
SCL
CSN
BATTERY PACK
CELL N
CELL 1
OPTIONAL
10k NTC
THERMISTOR
PROTECTOR
HOST
µP
13Maxim Integrated
MAX17047/MAX17050
ModelGauge m3 Fuel Gauge
Figure 7. Operating Circuits that Share Pack Thermistor with System Charger
Recommended Layout
Proper circuit layout (see Figure 8) is essential for
measurement accuracy when using the MAX17047/
MAX17050 ModelGauge m3 ICs. The recommended
layout guidelines are as follows:
1) Mount RSNS as close as possible to PACK-. The
device shares both voltage and current measure-
ments on the CSP pin. Therefore, it is important to limit
the amount of trace resistance between the current-
sensing resistor and PACK-.
2) VBATT trace should make a Kelvin connection to
PACK+. The device shares the VBATT pin for both
voltage measurement and IC power. Limiting the
voltage loss through this trace is important to voltage-
measurement accuracy. PCB resistance that cannot
be removed can be compensated for during charac-
terization of the application cell.
3) CSN and CSP traces should make Kelvin connections
to RSNS. The device measures current differentially
through the CSN and CSP pins. Any shared high-
current paths on these traces will affect current-
measurement gain accuracy. PCB resistance that
cannot be removed can be compensated for during
characterization of the application cell.
4) VBATT capacitor trace loop area should be minimized.
The device shares the VBATT pin for both voltage mea-
surement and IC power. Limiting noise at the VBATT
pin is important to current-measurement accuracy.
5) REG capacitor trace loop area should be minimized.
The helps filter any noise from the internal regulated
supply.
6) There are no limitations on any other IC connection.
Connections to THRM, ALRT, SDA, SCL, VTT, and
AIN, as well as any external components mounted to
these pins, have no special layout requirements.
MAX17047
VOLTAGE BASED
ON EXISTING
CHARGER REQUIREMENTS
VBIAS
VSYSTEM
VBATT
THERMISTOR
INSIDE
CELL PACK
MAX17047 + CHARGER
WITH EXTERNAL BIAS
PK- PK-
CHARGER WITH
VTT + THRM
AVAILABLE
PP
VTT
THRM
CSP
AIN
MAX17047
VBIAS
2.8V < VBIAS < VINTERNAL + 0.6V
VSYSTEM
VBATT
THERMISTOR
INSIDE
CELL PACK
MAX17047 + CHARGER
WITH INTERNAL BIAS
CHARGER WITH
INTERNAL
BIAS
P
VTT
THRM
CSP
AIN
VINTERNAL
ON DURING
CHARGE
OFF DURING
DISCHARGE
14Maxim Integrated
MAX17047/MAX17050
ModelGauge m3 Fuel Gauge
ModelGauge m3 Registers
To calculate accurate results, ModelGauge m3 requires
information about the cell, the application, and real-time
information measured by the device. Figure 9 shows all
inputs and outputs to the algorithm grouped by category.
Analog input registers are the real-time measurements
of voltage, temperature, and current performed by the
device. Application-specific registers are programmed
by the customer to reflect the operation of the applica-
tion. The Cell Characterization Information registers
hold characterization data that models the behavior of
the cell over the operating range of the application. The
Algorithm Configuration registers allow the host to adjust
performance of the device for its application. The Save
and Restore registers allow an application to maintain
accuracy of the algorithm after the device has been
power cycled. The following sections describe each
register in detail.
ModelGauge Algorithm
Output Registers
The following registers hold the output results from the
ModelGauge m3 algorithm.
SOCMIX Register (0Dh)
The SOCMIX register holds the calculated present state
of charge of the cell before any empty compensation
adjustments are performed. The register value is stored
as a percentage with a resolution of 0.0039% per LSb.
If an 8-bit state-of-charge value is desired, the host can
discard the lower byte and use only the upper byte of the
register with a resolution of 1.0%. Figure 10 shows the
SOCMIX register format.
Figure 8. Proper Board Layout
MAX17050
POSITIVE
POWER BUS
POSITIVE
POWER BUS
NEGATIVE
POWER BUS
NEGATIVE
POWER BUS
SDA VBATT AIN
THRM ALRT SCL
CSP REG CSN
PACK+ PACK+
VBATT
VTT
AIN
SCL
SDA
CSN
THRM
ALRT
REG
REG
CSP
CREG
EP
RSNS RSNS
CVBATT CVBATT
PACK- PACK-
+
CREG
MAX17047
15Maxim Integrated
MAX17047/MAX17050
ModelGauge m3 Fuel Gauge
Figure 9. ModelGauge m3 Register Map
Figure 10. SOCMIX Register Format (Output)
ModelGauge ALGORITHM
VCELL
CURRENT
TEMPERATURE
AverageVCELL
AverageCurrent
AverageTemperature
FilterCFG
LearnCFG
RelaxCFG
MiscCFG
AtRate
ALGORITHM
CONFIGURATION
FullCapNom
Iavg_empty
CELL
CHARACTERIZATION
INFORMATION RCOMP0
TempCo
TempNom
TempLim
V_empty
CHARACTERIZATION
TABLE
FCTC
QResidual Table
ANALOG
INPUTS
DesignCap
ICHGTerm
FullSOCThr
V_empty
APPLICATION
SPECIFIC
FullCAP
FullCapNom
FSTAT
RemCapMIX
SOCREP
RemCapREP
SOCAV
RemCapAV
TTE
AGE
CYCLES
OCV
SOCMIX
ModelGauge
ALGORITHM
OUTPUTS
CYCLES
RCOMP0
TempCo
dQacc
dPacc
FullCAP
SAVE AND
RESTORE
INFORMATION
QResidual Table
MSB—ADDRESS 0Dh LSB—ADDRESS 0Dh
27262524232221202-1 2-2 2-3 2-4 2-5 2-6 2-7 2-8
MSb LSb MSb LSb
2-8 UNITS: 0.0039%
20 UNITS: 1.0%
16Maxim Integrated
MAX17047/MAX17050
ModelGauge m3 Fuel Gauge
RemCapMIX Register (0Fh)
The RemCapMIX register holds the calculated remain-
ing capacity of the cell before any empty compensation
adjustments are performed. The value is stored in terms
of FVh and must be divided by the application sense-
resistor value to determine remaining capacity in mAh.
Figure 11 shows the RemCapMIX register format.
SOCREP Register (06h)
SOCREP is a filtered version of the SOCAV register that
prevents large jumps in the reported value caused by
changes in the application such as abrupt changes in
load current. The register value is stored as a percent-
age with a resolution of 0.0039% per LSb. If an 8-bit SOC
value is desired, the host can discard the lower byte and
use only the upper byte of the register with a resolution
of 1.0%. Figure 12 shows the SOCREP register format.
RemCapREP Register (05h)
RemCapREP is a filtered version of the RemCapAV register
that prevents large jumps in the reported value caused by
changes in the application such as abrupt changes in load
current. The value is stored in terms of FVh and must be
divided by the application sense-resistor value to determine
remaining capacity in mAh. During application idle periods
where the AverageCurrent Register value is less than Q6
LSbs, RemCapREP does not change. The measured cur-
rent during this period is still accumulated into RemCapMIX
and is slowly reflected in RemCapREP once cell loading or
charging occurs. Figure 13 shows the RemCapREP register
format.
Figure 11. RemCapMIX Register Format (Output)
Figure 12. SOCREP Register Format (Output)
Figure 13. RemCapREP Register Format (Output)
MSB—ADDRESS 0Fh LSB—ADDRESS 0Fh
215 214 213 212 211 210 29282726252423222120
MSb LSb MSb LSb
20 UNITS: 5.0FVh/RSENSE
(0.5mAh WHEN RSENSE = 0.010I)
MSB—ADDRESS 06h LSB—ADDRESS 06h
27262524232221202-1 2-2 2-3 2-4 2-5 2-6 2-7 2-8
MSb LSb MSb LSb
2-8 UNITS: 0.0039%
20 UNITS: 1.0%
MSB—ADDRESS 05h LSB—ADDRESS 05h
215 214 213 212 211 210 29282726252423222120
MSb LSb MSb LSb
20 UNITS: 5.0FVh/RSENSE
(0.5mAh WHEN RSENSE = 0.010I)
17Maxim Integrated
MAX17047/MAX17050
ModelGauge m3 Fuel Gauge
SOCAV Register (0Eh)
The SOCAV register holds the calculated present state
of charge of the cell based on all inputs from the
ModelGauge m3 algorithm including empty compensa-
tion. The register value is stored as a percentage with a
resolution of 0.0039% per LSb. If an 8-bit state-of-charge
value is desired, the host can discard the lower byte and
use only the upper byte of the register with a resolution of
1.0%. The SOCAV register value is an unfiltered calcula-
tion. Jumps in the value can be caused by changes in
the application such as abrupt changes in load current.
Figure 14 shows the SOCAV register format.
RemCapAV Register (1Fh)
The RemCapAV register holds the calculated remain-
ing capacity of the cell based on all inputs from the
ModelGauge m3 algorithm including empty compen-
sation. The value is stored in terms of FVh and must
be divided by the application sense-resistor value to
determine the remaining capacity in mAh. The register
value is an unfiltered calculation. Jumps in the value can
be caused by changes in the application such as abrupt
changes in load current. Figure 15 shows the RemCapAV
register format.
SOCVF Register (FFh)
The SOCVF register holds the calculated present SOC of
the battery according to the voltage fuel gauge. The reg-
ister value is stored as a percentage with a resolution of
0.0039% per LSb. If an 8-bit SOC value is desired, the host
can discard the lower byte and use only the upper byte of
the register with a resolution of 1.0%. Figure 16 shows the
SOCVF register format.
TTE Register (11h)
The TTE register holds the estimated time to empty for
the application under present conditions. The TTE value
is determined by dividing the RemCapAV register by the
AverageCurrent register. The result is stored in the TTE
register with a resolution of 5.625s per LSb.
Figure 14. SOCAV Register Format (Output)
Figure 15. RemCapAV Register Format (Output)
Figure 16. SOCVF Register Format (Output)
MSB—ADDRESS 0Eh LSB—ADDRESS 0Eh
27262524232221202-1 2-2 2-3 2-4 2-5 2-6 2-7 2-8
MSb LSb MSb LSb
2-8 UNITS: 0.0039%
20 UNITS: 1.0%
MSB—ADDRESS 1Fh LSB—ADDRESS 1Fh
215 214 213 212 211 210 29282726252423222120
MSb LSb MSb LSb
20 UNITS: 5.0FVh/RSENSE
(0.5mAh WHEN RSENSE = 0.010I)
MSB—ADDRESS FFh LSB—ADDRESS FFh
27262524232221202-1 2-2 2-3 2-4 2-5 2-6 2-7 2-8
MSb LSb MSb LSb
2-8 UNITS: 0.0039%
20 UNITS: 1.0%
18Maxim Integrated
MAX17047/MAX17050
ModelGauge m3 Fuel Gauge
Figure 17. TTE Register Format (Output)
Figure 18. Age Register Format (Output)
Alternatively, the TTE register can be used to estimate time
to empty for any given current load. Whenever the AtRate
register is programmed to a negative number, representing
a discharge current, the TTE register displays the estimated
time to empty for the application based on the AtRate regis-
ter value. Figure 17 shows the TTE register format.
Age Register (07h)
The Age register contains a calculated percentage value
of the application’s present cell capacity compared to its
expected capacity. The result can be used by the host to
gauge the cell’s health as compared to a new cell of the
same type. The result is displayed as a percentage value
from 0 to 256% with a 0.0039% LSb. Figure 18 shows the
Age register format. The equation for the register output is:
Age Register = 100% O (FullCAP Register/
DesignCap Register)
Cycles Register (17h)
The Cycles register accumulates total percent change in
the cell during both charging and discharging. The result
is stored as a total count of full charge/discharge cycles.
For example, a full charge/discharge cycle results in
the Cycles register incrementing by 100%. The Cycles
register has a full range of 0 to 65535% with a 1% LSb.
This register is reset to 0% at power-up. To maintain the
lifetime cycle count of the cell, this register must be peri-
odically saved by the host and rewritten to the device at
power-up. See the Save and Restore Registers section
for details. See Figure 19 for the Cycles register format.
VFOCV Register (FBh)
The VFOCV register contains the raw open-circuit volt-
age output of the voltage fuel gauge. This value is used
in other internal calculations and can be read for debug
purposes. The result is a 12-bit value ranging from 2.5V
to 5.119V where 1 LSb is 1.25mV. The bottom 4 bits of
this register are don’t care bits. See Figure 20 for the
VFOCV register format.
Figure 19. Cycles Register Format (Output)
MSB—ADDRESS 11h LSB—ADDRESS 11h
210 292827262524232221202-1 2-2 2-3 2-4 2-5
MSb LSb MSb LSb
20 UNITS: 3.0min
MSB—ADDRESS 07h LSB—ADDRESS 07h
27262524232221202-1 2-2 2-3 2-4 2-5 2-6 2-7 2-8
MSb LSb MSb LSb
20 UNITS: 1.0%
2-8 UNITS: 0.0039%
MSB—ADDRESS 17h LSB—ADDRESS 17h
215 214 213 212 211 210 29282726252423222120
MSb LSb MSb LSb
20 UNITS: 1.0%
19Maxim Integrated
MAX17047/MAX17050
ModelGauge m3 Fuel Gauge
FullCAP Register (10h)
This register holds the ModelGauge m3 algorithm calcu-
lated full capacity of the cell under best-case conditions
(light load, hot). A new full-capacity value is calculated
after the end of every charge cycle in the application. The
value is stored in terms of FVh and must be divided by
the application sense-resistor value to determine capac-
ity in mAh. Figure 21 is the FullCAP register format. See
the End-of-Charge Detection section.
FullCapNom Register (23h)
This register holds the calculated full capacity of the cell,
not including temperature and charger tolerance. New
full capacity values are calculated periodically by the IC
during operation. The value is stored in terms of FVh and
must be divided by the application sense resistor value
to determine capacity in mAh. This register is used to
calculate the outputs of the ModelGauge m3 algorithm
and is available to the user only for debug. Figure 22 is
the FullCapNom register format.
Figure 20. VFOCV Register Format (Output)
Figure 21. FullCAP Register Format (Output)
Figure 22. FullCapNom Register Format (Output)
MSB—ADDRESS FBh LSB—ADDRESS FBh
211 210 29282726252423222120XXXX
MSb LSb MSb LSb
20 UNITS: 1.25mV
X = DON’T CARE
MSB—ADDRESS 10h LSB—ADDRESS 10h
215 214 213 212 211 210 29282726252423222120
MSb LSb MSb LSb
20 UNITS: 5.0FVh/RSENSE
(0.5mAh WHEN RSENSE = 0.010I)
MSB—ADDRESS 23h LSB—ADDRESS 23h
215 214 213 212 211 210 29282726252423222120
MSb LSb MSb LSb
20 UNITS: 5.0FVh/RSENSE
(0.5mAh WHEN RSENSE = 0.010I)
20Maxim Integrated
MAX17047/MAX17050
ModelGauge m3 Fuel Gauge
QH Register (4Dh)
The QH register displays the raw coulomb count gener-
ated by the device. This register is used internally as an
input to the mixing algorithm. Monitoring changes in QH
over time can be useful for debugging device operation.
The QH register is set to 0000h at power-up. The QH reg-
ister format is shown in Figure 23.
Application-Specific Registers
The following registers define the behavior of the applica-
tion. They must be programmed by the user before the
ModelGauge m3 algorithm is accurate. Any changes to
these register values require recharacterization of the cell.
DesignCap Register (18h)
The DesignCap register holds the expected capacity of
the cell. This value is used to determine age and health
of the cell by comparing against the calculated pres-
ent capacity stored in the FullCAP register. DesignCap
has an LSb equal to 5.0FVh and a full range of 0 to
327.68mVh. The user should multiply the mAh capac-
ity of the cell by the sense resistor value to determine
the FVh value to store in the DesignCap register. The
DesignCap register format is shown in Figure 24.
FullSOCThr Register (13h)
The FullSOCThr register gates detection of end-of-
charge. SOCVF must be larger than the FullSOCThr
value before ICHGTerm is compared to the
AverageCurrent register value. The recommended
FullSOCThr register setting for most applications is 95%.
See the ICHGTerm register description for details. The
FullSOCThr register is 70% at power-up. Figure 25 is the
FullSOCThr register format.
Figure 23. QH Register Format (Output)
Figure 24. DesignCap Register Format (Input)
Figure 25. FullSOCThr Register Format (Input)
MSB—ADDRESS 23h LSB—ADDRESS 23h
215 214 213 212 211 210 29282726252423222120
MSb LSb MSb LSb
20 UNITS: 5.0FVh/RSENSE
(0.5mAh WHEN RSENSE = 0.010I)
MSB—Address 4Dh LSB—ADDRESS 4Dh
215 214 213 212 211 210 29282726252423222120
MSb LSb MSb LSb
20 UNITS: 5.0FVh/RSENSE
(0.5mAh WHEN RSENSE = 0.010I)
MSB—ADDRESS 18h LSB—ADDRESS 18h
27262524232221202-1 2-2 2-3 2-4 2-5 2-6 2-7 2-8
MSb LSb MSb LSb
2-8 UNITS: 0.0039%
20 UNITS: 1.0%
21Maxim Integrated
MAX17047/MAX17050
ModelGauge m3 Fuel Gauge
End-of-Charge Detection
The device detects the end of a charge cycle when
the application current falls into the band set by the
ICHGTerm register value. By monitoring both the Current
and AverageCurrent registers, the device can reject false
end-of-charge events such as application load spikes
or early charge-source removal. See the End-of-Charge
Detection graph in the Typical Operating Characteristics
and Figure 26.
Figure 26. False End-of-Charge Events
AVERAGE CURRENT
CURRENT
0mA
AVERAGE CURRENT
CURRENT
1.25 x ICHGTerm
0.125 x ICHGTerm
1.25 x ICHGTerm
0.125 x ICHGTerm
0mA
CHARGING
CHARGING
DISCHARGING
DISCHARGING
HIGH-CURRENT LOAD SPIKES DO NOT GENERATE END-OF-CHARGE
DETECTION BECAUSE CURRENT AND AVERAGE CURRENT READINGS
DO NOT FALL INTO THE DETECTION AREA AT THE SAME TIME.
EARLY CHARGER REMOVAL DOES NOT GENERATE END-OF-CHARGE
DETECTION BECAUSE CURRENT AND AVERAGE CURRENT READINGS
DO NOT FALL INTO THE DETECTION AREA AT THE SAME TIME.
22Maxim Integrated
MAX17047/MAX17050
ModelGauge m3 Fuel Gauge
When a proper end-of-charge event is detected, the
device learns a new FullCAP register value based on
the RemCapREP output. If the old FullCAP value was too
high, it is adjusted downward after the last valid end-
of-charge detection. If the old FullCAP was too low, it is
adjusted upward to match RemCapREP. This prevents
the calculated state of charge from ever reporting a value
greater than 100%. See Figure 27.
ICHGTerm Register (1Eh)
The ICHGTerm register allows the device to detect when
a charge cycle of the cell has completed. The host
should set the ICHGTerm register value equal to the
exact charge termination current used in the application.
The device detects end of charge if all the following con-
ditions are met:
• SOCVF > FullSOCThr
• ANDICHGTermx0.125<Current<ICHGTermx1.25
• AND ICHGTerm x 0.125 < AverageCurrent <
ICHGTerm x 1.25
Values are stored in FV. Multiply the termination current
by the sense resistor to determine the desired register
value. This register has the same range and resolution
as the Current register. Figure 28 shows the ICHGTerm
register format. ICHGTerm defaults to 150mA (03C0h) at
power-up.
Figure 27. FullCAP Learning at End of Charge
AVERAGE CURRENT
CURRENT
0mA
AVERAGE CURRENT
CURRENT
1.25 x ICHGTerm
0.125 x ICHGTerm
1.25 x ICHGTerm
0.125 x ICHGTerm
0mA
CHARGING
CHARGING
DISCHARGING
DISCHARGING
HIGH-CURRENT LOAD SPIKES DO NOT GENERATE END-OF-CHARGE
DETECTION BECAUSE CURRENT AND AVERAGE CURRENT READINGS
DO NOT FALL INTO THE DETECTION AREA AT THE SAME TIME.
EARLY CHARGER REMOVAL DOES NOT GENERATE END-OF-CHARGE
DETECTION BECAUSE CURRENT AND AVERAGE CURRENT READINGS
DO NOT FALL INTO THE DETECTION AREA AT THE SAME TIME.
23Maxim Integrated
MAX17047/MAX17050
ModelGauge m3 Fuel Gauge
V_empty Register (3Ah)
The V_empty register sets thresholds related to empty
detection during operation. Figure 29 is the V_empty
register format.
VE8:VE0—Empty Voltage. Sets the voltage level for
detecting empty. A 10mV resolution gives a 0 to 5.11V
range. This value is written to 3.12V at power-up.
VR6:VR0—Recovery Voltage. Sets the voltage level for
clearing empty detection. Once the cell voltage rises
above this point, empty voltage detection is reenabled.
A 40mV resolution gives a 0 to 5.08V range. This value is
written to 3.68V at power-up.
Cell Characterization
Information Registers
Proper cell characterization is required to achieve accu-
racy. The following registers (Table 1) hold information
that must be generated through a cell-characterization
procedure. Maxim provides a cell-characterization ser-
vice. Contact the factory for details.
Figure 28. ICHGTerm Register Format (Input)
Figure 29. V_empty Register Format (Input)
Table 1. Cell Characterization Information
Registers
REGISTER ADDRESS
Characterization Table (48 words) 80h to AFh
FullCap 10h
DesignCap 18h
ICHGTerm 1Eh
FullCapNom 23h
RCOMP0 38h
lavg_empty 36h
TempCo 39h
QResidual 00 12h
QResidual 10 22h
QResidual 20 32h
QResidual 30 42h
MSB—ADDRESS 1Eh LSB—ADDRESS 1Eh
S 214 213 212 211 210 29282726252423222120
MSb LSb MSb LSb
UNITS: 1.5625FV/RSENSE
MSB—ADDRESS 3Ah LSB—ADDRESS 3Ah
VE8VE8VE6VE5VE4VE3VE2VE1VE0VR6VR5VR4VR3VR2VR1VR0
MSb LSb MSb LSb
VR0 UNITS: 40mV
VE0 UNITS: 10mV
24Maxim Integrated
MAX17047/MAX17050
ModelGauge m3 Fuel Gauge
Algorithm Configuration Registers
The following registers allow operation of the ModelGauge
m3 algorithm to be adjusted for the application. It is recom-
mended that the default values for these registers be used.
FilterCFG Register (29h)
The FilterCFG register sets the averaging time period for
all A/D readings, for mixing OCV results and coulomb-
count results. It is recommended that these values are
not changed unless absolutely required by the applica-
tion. Figure 30 shows the FilterCFG register format:
CURR3:CURR0—Sets the time constant for the
AverageCurrent register. The default POR value of 4h gives
a time constant of 11.25 seconds. The equation setting the
period is:
AverageCurrent time constant = 175.8ms O 2(2+CURR)
VOLT2:VOLT0—Sets the time constant for the
AverageVCELL register. The default POR value of 2h gives
a time constant of 45.0s. The equation setting the period is:
AverageVCELL time constant = 175.8ms O 2(6+VOLT)
MIX3:MIX0—Sets the time constant for the mixing algo-
rithm. The default POR value of Dh gives a time constant
of 12.8 hours. The equation setting the period is:
Mixing Period = 175.8ms O 2(5+MIX)
TEMP2:TEMP0—Sets the time constant for the
AverageTemperature register. The default POR value of
1h gives a time constant of 12min. The equation setting
the period is:
AvergeTemperature time constant = 175.8ms x 2(8 + TEMP)
X—Reserved. Do not modify.
RelaxCFG Register (2Ah)
The RelaxCFG register defines how the device detects
if the cell is in a relaxed state. See Figure 32. For a cell
to be considered relaxed, current flow through the cell
must be kept at a minimum while the change in the cell’s
voltage over time, dV/dt, shows little or no change. If
AverageCurrent remains below the Load threshold while
VCELL changes less than the dV threshold over two
consecutive periods of dt, the cell is considered relaxed.
Figure 31 shows the RelaxCFG register format:
Load6:Load0—Sets the threshold, which the
AverageCurrent register is compared against. The
AverageCurrent register must remain below this thresh-
old value for the cell to be considered unloaded. Load is
an unsigned 7-bit value where 1 LSb = 50FV. The default
value is 800FV.
Figure 31. RelaxCFG Register Format (Input)
Figure 30. FilterCFG Register Format (Input)
MSB—ADDRESS 2Ah LSB—ADDRESS 2Ah
Load6Load5Load4Load3Load2Load1Load0dV4 dV3 dV2 dV1 dV0 dt3 dt2 dt1 dt0
MSb LSb MSb LSb
LOAD0 UNITS: 50FV/RSENSE
(5.0mAh WHEN RSENSE = 0.010I)
MSB—ADDRESS 29h LSB—ADDRESS 29h
X X TEMP
2
TEMP
1
TEMP
0MIX3 MIX2 MIX1 MIX0 VOLT2 VOLT1 VOLT0 CURR
3
CURR
2
CURR
1
CURR
0
MSb LSb MSb LSb
25Maxim Integrated
MAX17047/MAX17050
ModelGauge m3 Fuel Gauge
dV4:dV0—Sets the threshold, which VCELL is compared
against. If the cell’s voltage changes by less than dV over
two consecutive periods set by dt, the cell is considered
relaxed; dV has a range of 0 to 40mV where 1 LSb =
1.25mV. The default value is 1.75mV.
dt3:dt0—Sets the time period over which change in
VCELL is compared against dV. If the cell’s voltage
changes by less than dV over two consecutive periods
set by dt, the cell is considered relaxed. The default value
is 6 minutes. The comparison period is calculated as:
Relaxation Period = 2dt O 0.1758s
LearnCFG Register (28h)
The LearnCFG register controls all functions relating
to adaptation during operation. The LearnCFG register
default values should not be changed unless specifically
required by the application. Figure 33 is the LearnCFG
register format:
0—Bit must be written 0. Do not write 1.
1—Bit must be written 1. Do not write 0.
Filt Empty—Empty Detect Filter. This bit selects whether
empty is detected by a filtered or unfiltered voltage read-
ing. Setting this bit to 1 causes the empty detection algo-
rithm to use the AverageVCELL register. Setting this bit to
0 forces the empty detection algorithm to use the VCELL
register. This bit is written to 0 at power-up.
Figure 32. Cell Relaxation Detection
Figure 33. LearnCFG Register Format (Input/Output)
dt1 dt2 dt3 dt4 dt5dt6
48 TO 96
MINUTES
dV2
dV3
dV4
DISCHARGING
dV5 dV6
CELL UNLOADED
(RELAXATION BEGINS)
RELAXATION LOAD THRESHOLD
0
AVERAGE
CURRENT
CELL
VOLTAGE
FIRST
READING
BELOW
dv/dt
THRESHOLD
SECOND
READING
BELOW
dV/dt
THRESHOLD
CELL IS RELAXED
RelDt BIT SET
CELL CAPACITY IS
LEARNED
LONG RELAXATION
RelDt2 BIT SET
MSB—ADDRESS LSB—ADDRESS
0 0 1 0 0 1 1 0 0 LS2LS1LS00Filt
Empty 1 0
MSb LSb MSb LSb
26Maxim Integrated
MAX17047/MAX17050
ModelGauge m3 Fuel Gauge
Figure 34. MiscCFG Register Format (Input)
LS2:LS0—Learn Stage. See Figure 3 The Learn Stage
value controls the influence of the VFG on the mixing
algorithm. At power-up, Learn Stage defaults to 0h, mak-
ing the voltage fuel gauge dominate. Learn Stage then
advances to 7h over the course of two full cell cycles to
make the coulomb counter dominate. Host software can
write the Learn Stage value to 7h to advance to the final
stage at any time. Writing any value between 1h and
6h is ignored. Learn Stage reflects the D5, D6, and D7
bits of the Cycles register. Update the Cycles register
to advance to an intermediate state. For example, set
Cycles = 160% to advance to Learn Stage 5.
MiscCFG Register (2Bh)
The MiscCFG control register enables various other
functions of the device. The MiscCFG register default
values should not be changed unless specifically
required by the application. Figure 34 is the MiscCFG
register format:
0—Bit must be written 0. Do not write 1.
1—Bit must be written 1. Do not write 0.
X—Don’t Care. Bit may read 0 or 1.
SACFG1:SACFG0—SOC Alert Config. SOC Alerts can
be generated by monitoring any of the SOC registers as
follows. SACFG defaults to 00 at power-up:
0 0 SOC Alerts are generated based on the SOCREP
register.
0 1 SOC Alerts are generated based on the SOCAV
register.
1 0 SOC Alerts are generated based on the SOCMIX
register.
1 1 SOC Alerts are generated based on the SOCVF
register.
MR4:MR0—Mixing Rate. This value sets the strength of
the servo mixing rate after the final mixing state has been
reached (> 2.08 complete cycles). The units are MR0 =
6.25FV, giving a range up to 19.375mA with a standard
0.010I sense resistor. Setting this value to 00000b dis-
ables servo mixing and the IC continues with time-con-
stant mixing indefinitely. The default setting is 18.75FV or
1.875mA with a standard sense resistor.
enBi1—Enable reset on battery-insertion detection. Set
this bit to 1 to force a reset of the fuel gauge whenever a
battery insertion is detected based on AIN pin monitoring.
This bit is written to 1 at power-up.
FSTAT Register (3Dh)
The FSTAT register is a read-only register that monitors
the status of the ModelGauge algorithm. Do not write
to this register location. Figure 35 is the FSTAT register
format:
RelDt—Relaxed cell detection. This bit is set to a 1 when-
ever the ModelGauge m3 algorithm detects that the cell
is in a fully relaxed state. This bit is cleared to 0 whenever
a current greater than the Load threshold is detected.
See Figure 32.
Figure 35. FSTAT Register Format (Output)
MSB—ADDRESS 2Bh LSB—ADDRESS 2Bh
0 0 X X enBi1 0 MR4MR3MR2MR1MR01 0 0 SACFG
1
SACFG
0
MSb LSb MSb LSb
MR0 UNITS: 6.25µV
MSB—ADDRESS 3Dh LSB—ADDRESS 3Dh
X X X X X X RelDt EDet X RelDt2 X X X X X DNR
MSb LSb MSb LSb
27Maxim Integrated
MAX17047/MAX17050
ModelGauge m3 Fuel Gauge
RelDt2—Long Relaxation. This bit is set to a 1 whenever
the ModelGauge m3 algorithm detects that the cell has
been relaxed for a period of 48 to 96 minutes or longer.
This bit is cleared to 0 whenever the cell is no longer in a
relaxed state. See Figure 32.
DNR—Data Not Ready. This bit is set to 1 at cell inser-
tion and remains set until the output registers have been
updated. Afterwards, the IC clears this bit indicating the
fuel gauge calculations are now up to date. This takes
between 445ms and 1.845s depending on whether the
IC was in a powered state prior to the cell-insertion event.
EDet—Empty Detection. This bit is set to 1 when the IC
detects that the cell empty point has been reached. This
bit is reset to 0 when the cell voltage rises above the
recovery threshold. See the V_empty register for details.
X—Don’t Care. This bit is undefined and can be logic
0 or 1.
AtRate Register (04h)
The AtRate register allows host software to estimate
remaining capacity, SOC, and time to empty for a theo-
retical load current. Whenever the AtRate register is pro-
grammed to 0 or a positive value, the device uses A/D
measurements for determining the SOCAV, RemCapAV,
and TTE register values. Whenever the AtRate register is
programmed to a negative value indicating a hypotheti-
cal discharge current, the SOCAV, RemCapAV, and TTE
registers calculate their values for the AtRate register
theoretical current instead. The AtRate register holds a
two’s-complement 16-bit value. Do not write 8000h to
this register. Figure 36 shows the AtRate register format.
Power-Up and Power-On Reset
Any power-on reset (POR) of the device resets all
memory locations to their default POR value. This
removes any custom cell characterization and applica-
tion data, affects ALRT interrupt and shutdown mode set-
tings, and resets all learned adjustments made by the fuel
gauge. To maintain accuracy of the fuel gauge and reset
operation settings of the device, the host must reload
all application memory data and restore all learned fuel-
gauge information. Note that the device may take up to
445ms to completely reset operation after a POR event
occurs. See Figure 37. Saved data should not be restored
until after this period is over. The following procedure is
recommended:
1) Read Status register. If POR = 0, exit.
2) Wait 600ms for POR operation to fully complete.
3) Restore all application register values.
4) Restore fuel gauge learned-value information (see the
Save and Restore Registers section).
5) Clear POR bit.
Figure 36. AtRate Register Format (Input)
MSB—ADDRESS 04h LSB—ADDRESS 04h
S 214 213 212 211 210 29282726252423222120
MSb LSb MSb LSb
20 UNITS: 1.5625FV/RSENSE
X = DON’T CARE
28Maxim Integrated
MAX17047/MAX17050
ModelGauge m3 Fuel Gauge
Save and Restore Registers
The device is designed to operate outside the battery
pack and can therefore be exposed to power loss when
in the application. To prevent the loss of learned informa-
tion during power cycles, a save-and-restore procedure
can be used to maintain register values in nonvolatile
memory external to the device. The registers (Table 2)
must be stored externally and then rewritten to the device
after power-up to maintain a learned state of operation.
Note that some registers are application outputs, some
registers are for internal calculations, and some are
characterization setup registers. Registers that are not
internal are described in their own sections. These values
should be stored by the application at periodic intervals.
Some recommended back-up events are:
• End-of-charge
• End-of-discharge
• Priortoapplicationenteringshutdownstate
The host is responsible for loading the default character-
ization data at first power-up of the device, and restoring
the default characterization data plus learned information
on subsequent power-up events.
Battery Removal and Insertion
The device detects when a cell has been removed or
inserted into the application. This allows the device to
adjust to the new cell to maintain accuracy. The removal-
detection feature also allows the device to quickly warn the
host processor through interrupt of impending power loss
if enabled.
Table 2. Save and Restore Registers
Figure 37. Power-Up Operation
REGISTER ADDRESS
FullCap 10h
Cycles 17h
RCOMP0 38h
TempCo 39h
QResidual 00 12h
QResidual 10 22h
QResidual 20 32h
QResidual 30 42h
dQacc 45h
dPacc 46h
AIN
VBATT
A/D
READINGS
OUTPUT
REGISTERS
1.4s UNTIL NEXT TEMPERATURE READING
270ms
175ms
CELL
INSERTION VBATT > VDDMIN A/D
MEASUREMENTS
COMPLETE
SOC VALUES
UPDATED
29Maxim Integrated
MAX17047/MAX17050
ModelGauge m3 Fuel Gauge
Detection occurs by monitoring the AIN pin voltage com-
pared to the THRM pin. Whenever a cell is present, the
external resistor-divider network sets the voltage of AIN.
When the cell is removed, the remaining external resistor
pulls AIN to the THRM pin voltage level. Whenever VAIN
< VTHRM - VDETF, the device determines that a cell is
present in the application. If VAIN > VTHRM - VDETR, the
device determines that no cell is present at that time.
Cell Insertion (IC Already Powered)
The device is ready to detect a cell insertion if either the
ETHRM or FTHRM bits of the CONFIG register are set
to enable the THRM pin output. See Figure 38. When a
cell insertion is detected, the fuel gauge is reset and all
fuel-gauge outputs are updated to reflect the SOC of the
newly inserted cell. This process can take up to 1.845s
(FTHRM = 0) or 620ms (FTHRM = 1) from time of inser-
tion. Note that the device uses the cell voltage as a start-
ing point for the fuel gauge. If the cell voltage is not fully
relaxed at time of insertion, the fuel gauge begins with
some initial error. See the Fuel-Gauge Learning section
for details. The host can disable this feature by clearing
the enBi1 bit in the MiscCFG register.
The device can also be configured to alert the host when
cell insertion occurs. When Bei = 1 in the CONFIG reg-
ister, the device generates an interrupt on the ALRT pin
at the start of the first temperature conversion after inser-
tion. This could take up to 1.4s to occur. This feature is
useful if the application uses more than one cell type and
the IC must be reconfigured at each insertion.
Figure 38. Operation After Cell Insertion
AIN
CELL INSERTION FROM POWERED STATE (FTHRM = 0)
CELL INSERTION FROM POWERED STATE (FTHRM = 1)
VBATT
A/D
READINGS
OUTPUT
REGISTERS
AIN
VBATT
A/D
READINGS
OUTPUT
REGISTERS
CELL
INSERTION
CELL
INSERTION
DETECTED
A/D
MEASUREMENTS
COMPLETE
SOC VALUES
UPDATED
CELL
INSERTION
CELL
INSERTION
DETECTED
A/D
MEASUREMENTS
COMPLETE
SOC VALUES
UPDATED
UP TO 1.4s
270ms
175ms
UP TO
175ms
270ms
175ms
30Maxim Integrated
MAX17047/MAX17050
ModelGauge m3 Fuel Gauge
Figure 39. Fast Detection of Cell Removal
Cell Removal
The device detects a cell removal if either the ETHRM or
FTHRM bits of the CONFIG register are set to enable the
THRM pin output. Cell removal does not affect IC opera-
tion. The device continues to update fuel-gauge outputs.
The host should monitor the Br and Bst bits of the Status
register to determine if the fuel-gauge outputs are valid.
The device can also be configured to alert the host when
cell removal occurs. When Ber = 1 in the CONFIG regis-
ter, the device generates an interrupt on the ALRT pin at
the start of the first temperature conversion after removal.
This could take up to 1.4s to occur. This feature is useful
if the application uses more than one cell type and the IC
must be reconfigured at each insertion.
Fast Detection of Cell Removal
The device can be configured to quickly alert the host of
impending power loss on cell removal. This fast response
allows the system to quickly and gracefully hibernate to
prevent power loss during battery swap. When Ber = 1,
FTHRM = 1, and ALRTp = 0 in the CONFIG register, an
interrupt on the ALRT pin is generated within 100Fs after
VAIN becomes greater than VTHRM - VDETR. If fast detec-
tion is used, it is recommended that all other IC interrupts
are disabled to prevent the host from spending time
determining the cause of the interrupt. Fast detection of
cell removal has no affect on fuel-gauge operation, but
leaving the external resistor-divider active increases cur-
rent consumption of the application. See Figure 39.
Modes of Operation
The device operates in one of two power modes: active
and shutdown. While in active mode, the device oper-
ates as a high-precision battery monitor with tempera-
ture, voltage, auxiliary inputs, current, and accumulated
current measurements acquired continuously, and the
resulting values updated in the measurement registers.
READ and WRITE access is allowed only in active mode.
In shutdown mode, the LDO is disabled and all
activity stops, although volatile RAM contents remain
preserved. All A/D register and fuel-gauge output values
are maintained. There are several options for entering
shutdown:
Entering shutdown:
• SHUTDOWN command—Write the CONFIG register
SHDN = 1 through the I2C interface; wait for longer
than the SHDNTIMER register value.
• Pack removal—Pack removal detection is valid for
longer than the SHDNTIMER register value and the
CONFIG register AINSH = 1.
• I2C shutdown—I2C lines both persist low for longer
than the SHDNTIMER register value and the CONFIG
register I2CSH = 1.
• ALRT shutdown—Shutdown occurs when the ALRT
line is externally driven low for longer than the
SHDNTIMER register value (ALSH = 1 and ALRTp =
0), or the ALRT line is externally driven high for longer
than the SHDNTIMER register value (ALSH = 1 and
ALRTp = 1). See the CONFIG Register (1Dh) section.
CELL REMOVAL
(Ber = 1, FTHRM = 1)
VBATT
AIN
CELL REMOVAL INTERRUPT GENERATED
< 100µs
ALRT
OUTPUT
31Maxim Integrated
MAX17047/MAX17050
ModelGauge m3 Fuel Gauge
Figure 40. Device State Based on Shutdown Exit Condition
These shutdown entry modes are all programmable
according to application. Shutdown events are gated
by the SHDNTIMER register, which allows a long delay
between the shutdown event and the actual shutdown.
By behaving this way, the device takes the best reading
of the relaxation voltage.
Exiting shutdown:
• I2C Wakeup—Any edge on SCL/SDA.
• ALRT Wakeup—Any edge on ALRT line and (ALSH =
1 or I2CSH = ALSH = 0).
• Reset—IC is power cycled.
See the Status and Configuration section for detailed
descriptions of the SHDNTIMER and CONFIG registers.
The state of the device when returning to active mode
differs depending on the triggering event. See Figure 40.
Host software can monitor the POR and Bi status bits to
determine what type of event has occurred.
ALRT Function
The Alert Threshold registers allow interrupts to be
generated by detecting a high or low voltage, a high or
low temperature, or a high or low SOC. Interrupts are
generated on the ALRT pin open-drain output driver. An
external pullup is required to generate a logic-high sig-
nal. Note that if the pin is configured to be logic-low when
inactive, the external pullup increases current drain.
The ALRTp bit in the CONFIG register sets the polarity of
the ALRT pin output. Alerts can be triggered by any of the
following conditions:
• Battery removal—(VAIN > VTHRM - VDETR) and bat-
tery removal detection enabled (Ber = 1).
• Battery insertion—(VAIN<VTHRM - VDETF) and bat-
tery insertion detection enabled (Bei = 1).
• Over-/undervoltage—VALRT threshold violation
(upper or lower) and alerts enabled (Aen = 1).
• Over-/undertemperature—TALRT threshold violation
(upper or lower) and alerts enabled (Aen = 1).
• Over/under SOC—SALRT threshold violation (upper
or lower) and alerts enabled (Aen = 1).
To prevent false interrupts, the threshold registers should
be initialized before setting the Aen bit. Alerts generated by
battery insertion or removal can only be reset by clearing
the corresponding bit in the Status register. Alerts gener-
ated by a threshold-level violation can be configured to
be cleared only by software, or cleared automatically
when the threshold level is no longer violated. See the
CONFIG (1Dh) register description for details of the alert
function configuration.
BATTERY INSERTION DETECTED
(THRM COMPARATOR RECOGNIZES CHANGE
FROM REMOVAL TO INSERTED STATE)
DNR = 1
Bi = 0
POR = 1
FUEL GAUGE RESET
MaxMinVoltage REGISTER (1Bh) RESET
Cycles REGISTER (17h) RESET
ALL OTHER RAM VALUES MAINTAINED
ALL RAM VALUES MAINTAINED
FUEL GAUGE RESTARTS FROM POINT MAINTAINED
WHEN SHUTDOWN WAS ENTERED
ALL RAM RESET TO DEFAULT VALUES
FUEL GAUGE RESET
POWER-ON RESET
(RECOVERY FROM POWER LOSS)
WAKE FROM SHUTDOWN STATE
(I2C EDGE OR ALRT EDGE DETECTED)
EVENT ACTION STATUS
INDICATORS
DNR = 1
Bi = 1
POR = UNCHANGED
DNR = 0
Bi = UNCHANGED
POR = UNCHANGED
32Maxim Integrated
MAX17047/MAX17050
ModelGauge m3 Fuel Gauge
Figure 41. VALRT Threshold Register Format (Input)
Figure 42. TALRT Threshold Register Format (Input)
VALRT Threshold Register (01h)
The VALRT Threshold register (Figure 41) sets upper
and lower limits that generate an ALRT pin interrupt if
exceeded by the VCELL register value. The upper 8
bits set the maximum value and the lower 8 bits set the
minimum value. Interrupt threshold limits are selectable
with 20mV resolution over the full operating range of the
VCELL register. At power-up, the thresholds default to
their maximum settings—FF00h (disabled).
TALRT Threshold Register (02h)
The TALRT Threshold register sets upper and lower limits
that generate an ALRT pin interrupt if exceeded by the
Temperature register value. The upper 8 bits set the max-
imum value and the lower 8 bits set the minimum value.
Interrupt threshold limits are stored in two’s-complement
format and are selectable with 1NC resolution over the full
operating range of the Temperature register. At power-
up, the thresholds default to their maximum settings—
7F80h (disabled). Figure 42 shows the TALRT Threshold
register format.
SALRT Threshold Register (03h)
The SALRT Threshold register (Figure 43) sets upper and
lower limits that generate an ALRT pin interrupt if exceeded
by the selected SOCREP, SOCAV, SOCMIX, or SOCVF
register values. See the SACFG bits in the MiscCFG
register description for details. The upper 8 bits set the
maximum value and the lower 8 bits set the minimum
value. Interrupt threshold limits are selectable with 1%
resolution over the full operating range of the selected
SOC register. At power-up, the thresholds default to their
maximum settings—FF00h (disabled).
Figure 43. SALRT Threshold Register Format (Input)
MSB—ADDRESS 01h LSB—ADDRESS 01h
MAX7MAX6MAX5MAX4MAX3MAX2MAX1MAX0MIN7MIN6MIN5MIN4MIN3MIN2MIN1MIN0
MSb LSb MSb LSb
UNITS: 20mV
MSB—ADDRESS 02h LSB—ADDRESS 02h
S MAX6MAX5MAX4MAX3MAX2MAX1MAX0S MIN6MIN5MIN4MIN3MIN2MIN1MIN0
MSb LSb MSb LSb
UNITS: 1NC
MSB—ADDRESS 03h LSB—ADDRESS 03h
MAX7MAX6MAX5MAX4MAX3MAX2MAX1MAX0MIN7MIN6MIN5MIN4MIN3MIN2MIN1MIN0
MSb LSb MSb LSb
UNITS: 1%
33Maxim Integrated
MAX17047/MAX17050
ModelGauge m3 Fuel Gauge
Figure 44. CONFIG Register Format (Input)
Status and Configuration
The following registers control operation of the ALRT inter-
rupt feature, control transition between active and shut-
down modes of operation, and provide status updates to
the host processor.
CONFIG Register (1Dh)
The CONFIG register holds all shutdown enable, alert
enable, and temperature enable control bits. Writing a
bit location enables the corresponding function within
a 175.8ms task period. Figure 44 shows the CONFIG
register format.
0—Bit must be written 0. Do not write 1.
Ber—Enable alert on battery removal. When Ber = 1, a
battery-removal condition, as detected by the AIN pin
voltage, triggers an alert. Set to 0 at power-up. Note that
if this bit is set to 1, the ALSH bit should be set to 0 to
prevent an alert condition from causing the device to
enter shutdown mode.
Bei—Enable alert on battery insertion. When Bei = 1, a
battery-insertion condition, as detected by the AIN pin
voltage, triggers an alert. Set to 0 at power-up. Note that
if this bit is set to 1, the ALSH bit should be set to 0 to
prevent an alert condition from causing the device to
enter shutdown mode.
Aen—Enable alert on fuel-gauge outputs. When Aen =
1, violation of any of the alert threshold register values by
temperature, voltage, or SOC triggers an alert. This bit
affects the ALRT pin operation only. The Smx, Smn, Tmx,
Tmn, Vmx, and Vmn bits are not disabled. This bit is set
to 0 at power-up. Note that if this bit is set to 1, the ALSH
bit should be set to 0 to prevent an alert condition from
causing the device to enter shutdown mode.
FTHRM—Force Thermistor Bias Switch. This allows the
host to control the bias of the thermistor switch or enable
fast detection of battery removal (see the Fast Detection
of Cell Removal section). Set FTHRM = 1 to always
enable the thermistor bias switch. With a standard 10kI
thermistor, this adds an additional ~200FA to the current
drain of the circuit. This bit is set to 0 at power-up.
ETHRM—Enable Thermistor. Set to logic 1 to enable
the automatic THRM output bias and AIN measurement
every 1.4s. This bit is set to 1 at power-up.
ALSH—ALRT Shutdown. Set to logic 1 and clear the
Aen, Ber, and Bei bits to configure the ALRT pin as an
input to control shutdown mode of the device. The device
enters shutdown if the ALRT pin is held active for longer
than timeout of the SHDNTIMER register. The device
enters active mode immediately on the opposite edge of
the ALRT pin. When set to logic 0, the ALRT pin can func-
tion as an interrupt output. This bit is set to 0 at power-up.
Note that if this bit is set to 1, the Bei, Ber, and Aen bits
should be set to 0 to prevent an alert condition from caus-
ing the device to enter shutdown mode.
I2CSH—I2C Shutdown. Set to logic 1 to force the device
to enter shutdown mode if both SDA and SCL are held
low for more than timeout of the SHDNTIMER register.
This also configures the device to wake up on a rising
edge of either SDA or SCL. Set to 1 at power-up. Note
that if I2CSH and AINSH are both set to 0, the device
wakes up an edge of any of the SDA, SCL, or ALRT pins.
SHDN—Shutdown. Write this bit to logic 1 to force a
shutdown of the device after timeout of the SHDNTIMER
register. SHDN is reset to 0 at power-up and upon exiting
shutdown mode.
Tex—Temperature External. When set to 1, the fuel gauge
requires external temperature measurements to be written
from the host. When set to 0, measurements on the AIN
pin are converted to a temperature value and stored in the
Temperature register instead. Tex is set to 1 at power-up.
Ten—Enable Temperature Channel. Set to 1 and set
ETHRM or FTHRM to 1 to enable measurements on the
AIN pin. Ten is set to 1 at power-up.
MSB—ADDRESS 1Dh LSB—ADDRESS 1Dh
0 SSTSVSALRTp AINSH Ten Tex SHDN I2CSH ALSH ETHRM FTHRM Aen Bei Ber
MSb LSb MSb LSb
34Maxim Integrated
MAX17047/MAX17050
ModelGauge m3 Fuel Gauge
Figure 46. SHDNTIMER Register Format (Input/Output)
Figure 45. Timer Register Format (Output)
AINSH—AIN Pin Shutdown. Set to 1 to enable device shut-
down when the battery is removed. The IC enters shutdown
if the AIN pin remains high (AIN reading > VTHRM - VDETR)
for longer than the timeout of the SHDNTIMER register. This
also configures the device to wake up when AIN is pulled low
on cell insertion. AINSH is set to 0 at power-up. Note that if
I2CSH and AINSH are both set to 0, the device wakes up an
edge of any of the SDA, SCL, or ALRT pins.
ALRTp—ALRT Pin Polarity. Regardless if ALRT is being
used as an input or output, if ALRTp = 0, the ALRT pin
is active low; if ALRTp = 1, the ALRT pin is active high.
ALRTp must be set to 0 to enable fast detection of cell
removal. ALRTp is set to 0 at power-up.
VS—Voltage ALRT Sticky. When VS = 1, voltage alerts
can only be cleared through software. When VS = 0, volt-
age alerts are cleared automatically when the threshold
is no longer exceeded. VS is set to 0 at power-up.
TS—Temperature ALRT Sticky. When TS = 1, tempera-
ture alerts can only be cleared through software. When
TS = 0, temperature alerts are cleared automatically
when the threshold is no longer exceeded. TS is set to 1
at power-up.
SS—SOC ALRT Sticky. When SS = 1, SOC alerts can
only be cleared through software. When SS = 0, SOC
alerts are cleared automatically when the threshold is no
longer exceeded. SS is set to 0 at power-up.
TIMER Register (3Eh)
This register holds timing information for the fuel gauge.
It is available to the user for debug purposes. Figure 45
shows the TIMER register format.
SHDNTIMER Register (3Fh)
The SHDNTIMER register sets the timeout period from
when a shutdown event is detected until the device
disables the LDO and enters low-power mode. Figure 46
shows the SHDNTIMER register format.
CTR12:CTR0—Shutdown Counter. This register counts
the total amount of elapsed time since the shutdown trig-
ger event. This counter value stops and resets to 0 when
the shutdown timeout completes. The counter LSb is 1.4s.
THR2:THR0—Sets the shutdown timeout period from a
minimum of 45s to a maximum of 1.6h. The default POR
value of 7h gives a shutdown delay of 1.6h. The equation
setting the period is:
Shutdown Timeout Period = 175.8ms O 2(8+THR)
MSB—ADDRESS 3Fh LSB—ADDRESS 3Fh
THR2THR1THR0CTR12 CTR11 CTR10 CTR9CTR8CTR7CTR6CTR5CTR4CTR3CTR2CTR1CTR0
MSb LSb MSb LSb
MSB—Address 3Eh LSB—Address 3Eh
215 214 213 212 211 210 29282726252423222120
MSb LSb MSb LSb
20 UNITS: 175.8ms
35Maxim Integrated
MAX17047/MAX17050
ModelGauge m3 Fuel Gauge
Figure 47. Status Register Format (Input/Output)
Status Register (00h)
The Status register maintains all flags related to alert
thresholds and battery insertion or removal. Figure 47
shows the Status register format.
POR—Power-On Reset. This bit is set to a 1 when the
device detects that a software or hardware POR event
has occurred. If the host detects that the POR bit has
been set, the device should be reconfigured. See the
Power-Up and Power-On Reset section. This bit must be
cleared by system software to detect the next POR event.
POR is set to 1 at power-up.
Bst—Battery Status. This bit is set to 0 when a battery
is present in the system and set to 1 when the battery is
removed. Bst is set to 0 at power-up.
Vmn—Minimum VALRT Threshold Exceeded. This bit is
set to a 1 whenever a VCELL register reading is below
the minimum VALRT value. This bit may or may not need
to be cleared by system software to detect the next
event. See VS in the CONFIG register. Vmn is set to 0 at
power-up.
Tmn—Minimum TALRT Threshold Exceeded. This bit is
set to a 1 whenever a Temperature register reading is
below the minimum TALRT value. This bit may or may not
need to be cleared by system software to detect the next
event. See TS in the CONFIG register. Tmn is set to 0 at
power-up.
Smn—Minimum SOCALRT Threshold Exceeded. This
bit is set to a 1 whenever SOC falls below the minimum
SOCALRT value. This bit may or may not need to be
cleared by system software to detect the next event. See
SS in the CONFIG register and SACFG in the MiscCFG
register. Smn is set to 0 at power-up.
Bi—Battery Insertion. This bit is set to a 1 when the
device detects that a battery has been inserted into
the system by monitoring the AIN pin. This bit must be
cleared by system software to detect the next insertion
event. Bi is set to 0 at power-up.
Vmx—Maximum VALRT Threshold Exceeded. This bit is
set to a 1 whenever a VCELL register reading is above the
maximum VALRT value. This bit may or may not need to be
cleared by system software to detect the next event. See
VS in the CONFIG register. Vmx is set to 0 at power-up.
Tmx—Maximum TALRT Threshold Exceeded. This bit is
set to a 1 whenever a Temperature register reading is
above the maximum TALRT value. This bit may or may
not need to be cleared by system software to detect the
next event. See TS in the CONFIG register. Tmx is set to
0 at power-up.
Smx—Maximum SOCALRT Threshold Exceeded. This bit
is set to a 1 whenever SOC rises above the maximum
SOCALRT value. This bit may or may not need to be
cleared by system software to detect the next event. See
SS in the CONFIG register and SACFG in the MiscCFG
register. Smx is set to 0 at power-up.
Br—Battery Removal. This bit is set to a 1 when the
device detects that a battery has been removed from the
system. This bit must be cleared by system software to
detect the next removal event. Br is set to 0 at power-up.
X—Don’t Care. This bit is undefined and can be logic 0 or 1.
MSB—ADDRESS 00h LSB—ADDRESS 00h
Br Smx Tmx Vmx Bi Smn Tmn Vmn X X X X Bst X POR X
MSb LSb MSb LSb
36Maxim Integrated
MAX17047/MAX17050
ModelGauge m3 Fuel Gauge
Version Register (21h)
The Version register holds a 16-bit value that indicates
the version of the device. Figure 48 shows the Version
register format.
Voltage Measurement
While in active mode, the device periodically measures
the voltage between the VBATT and CSP pins over a 2.5V
to 4.98V range. The resulting data is placed in the VCELL
register every 175.8ms with an LSb value of 0.625mV.
Additionally, the device maintains a record of the mini-
mum and maximum voltage measured by the device,
and an average voltage over a time period defined by
the host. Contents of the VCELL and AverageVCELL
registers are indeterminate for the first conversion cycle
time period after device power-up. The last values of the
VCELL and AverageVCELL registers are maintained when
the device enters shutdown mode.
VCELL Register (09h)
While in active mode, the device periodically measures the
voltage between the VBATT and CSP pins over a 0 to 4.98V
range. The resulting data is placed in the VCELL register
every 175.8ms with an LSb value of 0.625mV. Voltages
above the maximum register value are reported as the
maximum value. The lower 3 bits of the VCELL register are
don’t care bits. Figure 49 shows the VCELL register format.
AverageVCELL Register (19h)
The AverageVCELL register reports an average of VCELL
register readings over a configurable 12s to 24min time
period. See the FilterCFG register description for details on
setting the time filter. The resulting average is placed in the
AverageVCELL register with an LSb value of 0.625mV. The
lower 3 bits of the AverageVCELL register are don’t care
bits.The first VCELL register reading after device power-
up sets the starting point of the AverageVCELL filter. Note
that when a cell relaxation event is detected, the averag-
ing period for the AverageVCELL register changes to the
period defined by dt3:dt0 in the RelaxCFG register. The
AverageVCELL register reverts back to its normal averag-
ing period when a charge or discharge current is detect-
ed. Figure 50 shows the AverageVCELL register format.
Figure 48. Version Register Format (Output)
Figure 49. VCELL Register Format (Output)
Figure 50. AverageVCELL Register Format (Output)
MSB—ADDRESS 21h LSB—ADDRESS 21h
V15 V14 V13 V12 V11 V10 V9V8V7V6V5V4V3V2V1V0
MSb LSb MSb LSb
MSB—ADDRESS 09h LSB—ADDRESS 09h
212 211 210 29282726252423222120XXX
MSb LSb MSb LSb
UNITS: 0.625mV
MSB—ADDRESS 19h LSB—ADDRESS 19h
212 211 210 29282726252423222120XXX
MSb LSb MSb LSb
UNITS: 0.625mV
37Maxim Integrated
MAX17047/MAX17050
ModelGauge m3 Fuel Gauge
Figure 51. MaxMinVCELL Register Format (Output)
MaxMinVCELL Register (1Bh)
The MaxMinVCELL register maintains the maximum and
minimum VCELL register values since the last fuel-gauge
reset or until reset by the host software. Each time the
VCELL register updates, it is compared against these
values. If VCELL is larger than the maximum or less than
the minimum, the corresponding value is replaced with
the new reading. At power-up, the MaxVCELL value is set
to 00h (the minimum) and the MinVCELL value is set to
FFh (the maximum). Therefore, both values are changed
to the VCELL register reading after the first update. Host
software can reset this register by writing it to its power-
up value of 00FFh. The maximum and minimum voltages
are each stored as 8-bit values with a 20mV resolution.
Figure 51 shows the MaxMinVCELL register format.
Current Measurement
While in active mode, the device periodically measures
the voltage between the CSN and CSP pins over a
Q51.2mV range. The resulting data is stored as a signed
two’s-complement value in the Current register every
175.8ms with an LSb value of 1.5625FV/RSENSE. All
devices are calibrated for current-measurement accu-
racy at the factory. However, if the application requires,
Current Register readings can be adjusted by changing
the COFF and CGAIN register settings.
Additionally, the device maintains a record of the mini-
mum and maximum current measured by the device,
and an average current over a time period defined by
the host. Contents of the Current and AverageCurrent
registers are 0000h until the first conversion cycle time
period after IC power-up. The last values of the Current
and AverageCurrent registers are maintained when the
IC enters shutdown mode.
Current Register (0Ah)
While in active mode, the device periodically measures the
voltage between the CSN and CSP pins over a Q51.2mV
range. The resulting data is stored as a two’s-complement
value in the Current register every 175.8ms with an LSb value
of 1.5625FV/RSENSE. Voltages outside the minimum and
maximum register values are reported as the minimum or
maximum value. Figure 52 shows the Current register format
and Table 3 shows the Sample Current register conversions.
Table 3. Sample Current Register Conversions
FUNCTION SENSE
RESISTOR (I)
CGAIN
REGISTER
CURRENT REGISTER
RESOLUTION (µA)
CURRENT REGISTER
RANGE (A)
MAXIMUM CELL
CAPACITY (Ah)
Adjusting sense
resistor to meet
range and accuracy
requirements
0.005 4000h 312.50 Q10.24 32.768
0.010 4000h 156.25 Q5.12 16.384
0.020 4000h 78.125 Q2.56 8.192
Adjusting CGAIN to
keep units constant
0.005 7FFFh 156.25 Q5.12 16.384
0.010 4000h 156.25 Q5.12 16.384
0.020 2000h 156.25 Q5.12 16.384
MSB—ADDRESS 1Bh LSB—ADDRESS 1Bh
MAX7MAX6MAX5MAX4MAX3MAX2MAX1MAX0MIN7MIN6MIN5MIN4MIN3MIN2MIN1MIN0
MSb LSb MSb LSb
UNITS: 20mV
38Maxim Integrated
MAX17047/MAX17050
ModelGauge m3 Fuel Gauge
Figure 54. MaxMinCurrent Register Format (Output)
Figure 53. AverageCurrent Register Format (Output)
AverageCurrent Register (0Bh)
The AverageCurrent register reports an average of
current-register readings over a configurable 0.7s to
6.4h time period. See the FilterCFG register descrip-
tion for details on setting the time filter. The resulting
average is placed in the AverageCurrent register with
an LSb value of 1.5625FV/RSENSE. The first Current
register reading after device power-up sets the start-
ing point of the AverageCurrent filter. The last value
of the AverageCurrent register is maintained when the
device enters shutdown mode. Figure 53 shows the
AverageCurrent register format.
MaxMinCurrent Register (1Ch)
The MaxMinCurrent register maintains the maximum and
minimum Current register values since the last fuel gauge
reset or until cleared by host software. Each time the
Current register updates, it is compared against these
values. If the reading is larger than the maximum or less
than the minimum, the corresponding value is replaced
with the new reading. At power-up, the MaxCurrent value
is set to 80h (the minimum) and the MinCurrent value is
set to 7Fh (the maximum). Therefore, both values are
changed to the Current register reading after the first
update. Host software can reset this register by writing it
to its power-up value of 807Fh. The maximum and mini-
mum voltages are each stored as two’s-complement 8-bit
values with 0.4mV/RSENSE resolution. Figure 54 shows
the MaxMinCurrent register format.
CGAIN Register (2Eh)/COFF Register (2Fh)
The CGAIN and COFF registers adjust the gain and off-
set of the current measurement result. The current mea-
surement A/D is factory trimmed to data-sheet accuracy
without the need for the user to make further adjustments.
The default power-up settings for CGAIN and COFF
apply no adjustments to the Current register reading. For
specific application requirements, the CGAIN and COFF
registers can be used to adjust readings as follows:
Current Register = Current A/D Reading O
(CGAIN Register/16384) + (2 O COFF Register)
For easiest software compatibility between systems,
configure CGAIN to keep current LSb resolution at
0.15625mA. A minimum sense resistance of 0.005I
is required due to the maximum range of CGAIN. This
preserves resolution of current readings and capacities.
Figure 52. Current Register Format (Output)
MSB—ADDRESS 1Ch LSB—ADDRESS 1Ch
S MAX6MAX5MAX4MAX3MAX2MAX1MAX0S MIN6MIN5MIN4MIN3MIN2MIN1MIN0
MSb LSb MSb LSb
UNITS: 0.4mV/RSENSE
MSB—ADDRESS 0Bh LSB—ADDRESS 0BH
S 214 213 212 211 210 29282726252423222120
MSb LSb MSb LSb
UNITS: 1.5625FV/RSENSE
MSB—ADDRESS 0Ah LSB—ADDRESS 0Ah
S 214 213 212 211 210 29282726252423222120
MSb LSb MSb LSb
UNITS: 1.5625FV/RSENSE
39Maxim Integrated
MAX17047/MAX17050
ModelGauge m3 Fuel Gauge
Table 4. Recommended TGAIN and TOFF Register Values for Common NTC
Thermistors
Figure 55. CGAIN Register Format (Input)
Figure 56. COFF Register Format (Input)
Both these registers are signed two’s complement. The
default values of 4000h for CGAIN and 0000h for COFF
preserve factory calibration and unit values (1.5625FV).
Figure 55 shows the CGAIN register format and Figure 56
shows the COFF register format.
Temperature Measurement
While in active mode and Ten = 1 in the CONFIG register,
the device periodically measures the voltage between
the AIN and CSP pins and compares the result to the volt-
age of the THRM pin. The device stores the result, a ratio-
metric value from 0 to 100%. The resulting data is placed
in the AIN register every 1.4s with an LSb of 0.0122%.
Conversions are initiated by connecting the THRM and
VTT pins internally. This enables the active pullup to
the external voltage-divider network. After the pullup is
enabled, the device waits for a settling period of tPRE
prior to making measurements on the AIN pin. When
ETHRM = 1, FTHRM = 0, the active pullup is disabled
when temperature measurements are complete. This fea-
ture limits the time the external resistor-divider network
is active and lowers the total amount of energy used by
the system.
When Tex = 0 and Ten = 1 in the CONFIG register, the
device converts the AIN register to a temperature using
the temperature gain (TGAIN) and temperature offset
(TOFF) register values:
Temperature Register = (AIN Register O
TGAIN Register/16384) + (TOFF Register O 2)
The resulting value is stored in the Temperature register
each time the AIN register is updated. Additionally, the
device maintains a record of the minimum and maximum
temperature measured by the device, and an average
temperature over a time period defined by the host.
Table 4 lists the recommended TGAIN and TOFF register
values for common NTC thermistors.
THERMISTOR R25C (kI)BETA RECOMMENDED TGAIN RECOMMENDED TOFF
Semitec
103AT-2 10 3435 E3E1h 290Eh
Fenwal
197-103LAG-A01 10 3974 E71Ch 251Ah
TDK
Type F 10 4550 E989h 22B1h
MSB—ADDRESS 2Eh LSB—ADDRESS 2Eh
S 202-1 2-2 2-3 2-4 2-5 2-6 2-7 2-8 2-9 2-10 2-11 2-12 2-13 2-14
MSb LSb MSb LSb
20 UNITS: 0.0061%
MSB—ADDRESS 2FH LSB—ADDRESS 2Fh
S 214 213 212 211 210 29282726252423222120
MSb LSb MSb LSb
UNITS: 3.125FV/RSENSE
40Maxim Integrated
MAX17047/MAX17050
ModelGauge m3 Fuel Gauge
Figure 57. AIN Register Format (Output)
Figure 58. Temperature Register Format (Input/Output)
When Tex = 1 in the CONFIG register, the device does
not update the Temperature register based on results
from the AIN pin A/D. Instead, host software must peri-
odically write the Temperature register with the known
application temperature to keep the fuel gauge accurate.
AIN Register (27h)
While in active mode and Ten = 1 in the CONFIG register,
the device periodically measures the voltage between
pins AIN and CSP and compares the result to the voltage
of the THRM pin. The device stores the result, a ratiomet-
ric value from 0 to 100%. The resulting data is placed
in the AIN register every 1.4s with an LSb of 0.0122%.
Contents of the AIN register are indeterminate for the
first conversion cycle time period after device power-up.
The last value of the AIN register is maintained when the
device enters shutdown mode or if Ten = 0 in the CONFIG
register. Figure 57 shows the AIN register format.
Temperature Register (08h)
While in active mode and Tex = 0 and Ten = 1 in the
CONFIG register, the device converts the AIN regis-
ter value into a signed two’s-complement temperature
value. See the TGAIN and TOFF configuration registers.
The resulting data is placed in the Temperature register
every 1.4s with a resolution of +0.0039NC. If an 8-bit
temperature reading is desired, the host can read only
the upper byte of the Temperature register with a resolu-
tion of +1.0NC. Contents of the Temperature register are
indeterminate for the first conversion cycle time period
after device power-up. The last value of the Temperature
register is maintained when the device enters shutdown
mode. Figure 58 shows the Temperature register format.
AverageTemperature Register (16h)
The AverageTemperature register reports an average
of temperature register readings over a configurable
6min to 12h time period. See the FilterCFG register (29h)
description for details on setting the time filter. The result-
ing average is placed in the AverageTemperature regis-
ter with an LSb value of 0.0039NC. The first Temperature
register reading after device power-up sets the starting
point of the AverageTemperature filter. The last value of
the AverageTemperature register is maintained when
the device enters shutdown mode. Figure 59 shows the
AverageTemperature register format.
Figure 59. AverageTemperature Register Format (Output)
MSB—ADDRESS 27h LSB—ADDRESS 27h
2-1 2-2 2-3 2-4 2-5 2-6 2-7 2-8 2-9 2-10 2-11 2-12 2-13 X X X
MSb LSb MSb LSb
2-13 UNITS: 0.0122%
MSB—ADDRESS 08h LSB—ADDRESS 08h
S 262524232221202-1 2-2 2-3 2-4 2-5 2-6 2-7 2-8
MSb LSb MSb LSb
2-8 UNITS: +0.0039NC
20 UNITS: +1.0NC
MSB—ADDRESS 16h LSB—ADDRESS 16h
S 262524232221202-1 2-2 2-3 2-4 2-5 2-6 2-7 2-8
MSb LSb MSb LSb
2-8 UNITS: +0.0039NC
20 UNITS: +1.0NC
41Maxim Integrated
MAX17047/MAX17050
ModelGauge m3 Fuel Gauge
Figure 61. TGAIN Register Format (Input)
Figure 60. MaxMinTemperature Register Format (Output)
MaxMinTemperature Register (1Ah)
The MaxMinTemperature register maintains the maxi-
mum and minimum Temperature register values since
the last fuel-gauge reset or until cleared by host software.
Each time the Temperature register updates, it is com-
pared against these values. If the reading is larger than
the maximum or less than the minimum, the correspond-
ing values are replaced with the new reading. At power-
up, the MaxTemperature value is set to 80h (minimum)
and the MinTemperature value is set to 7Fh (maximum).
Therefore, both values are changed to the Temperature
register reading after the first update. Host software can
reset this register by writing it to its power-up value of
807Fh. The maximum and minimum temperatures are
each stored as two’s complement 8-bit values with 1NC
resolution. Figure 60 shows the MaxMinTemperature
register format.
TGAIN Register (2Ch)/TOFF Register (2Dh)
The TGAIN and TOFF registers adjust the gain and offset
of the temperature measurement A/D on the AIN pin to
convert the result to a temperature value by the following
equation:
Temperature Register = (AIN Register O
TGAIN Register/16384) + (TOFF Register O 2)
Both these registers are signed two’s complement. These
registers allow for accurate temperature conversions when
using a variety of external NTC thermistors (see Table 4).
Figure 61 shows the TGAIN register format and Figure 62
shows the TOFF register format.
IC Memory Map
The device has a 256-word linear memory space con-
taining all user-accessible registers. All registers are
16 bits wide and are read and written as 2-byte values.
When the MSB of a register is read, the MSB and LSB
are latched simultaneously and held for the duration of
the Read Data command. This prevents updates to the
LSB during the read, ensuring synchronization between
the 2 register bytes.
All locations are volatile RAM and lose their data in the
event of power loss. Data is retained during device
shutdown. Each register has a power-on-reset value that
it defaults to at power-up. Word addresses designated
as reserved return an undetermined when read. These
locations
should not be written.
MSB—ADDRESS 2Ch LSB—ADDRESS 2Ch
S 214 213 212 211 210 29282726252423222120
MSb LSb MSb LSb
20 UNITS: +1NC/64
MSB—ADDRESS 1Ah LSB—ADDRESS 1Ah
S MAX6MAX5MAX4MAX3MAX2MAX1MAX0S MIN6MIN5MIN4MIN3MIN2MIN1MIN0
MSb LSb MSb LSb
UNITS: +1NC
42Maxim Integrated
MAX17047/MAX17050
ModelGauge m3 Fuel Gauge
Table 5. Device Memory Map
Figure 62. TOFF Register Format (Input)
ADDRESS
(HEX) REGISTER NAME A/D
MEASURE
ALERT/
STATUS
MG m3
APP
DATA
MG m3
CELL
DATA
MG m3
CONFIG
MG m3
SAVE AND
RESTORE
MG m3
OUTPUT
POR
VALUE
READ/
WRITE
00h Status ü0002h R/W
01h VALRT Threshold üFF00h R/W
02h TALRT Threshold ü7F80h R/W
03h SALRT Threshold üFF00h R/W
04h AtRate ü0000h R/W
05h RemCapREP ü03E8h R
06h SOCREP ü3200h R
07h Age ü6400h R
08h Temperature ü1600h R/W
09h VCELL üB400h R
0Ah Current ü0000h R
0Bh AverageCurrent ü0000h R
0Ch RESERVED — —
0Dh SOCMIX ü3200h R
0Eh SOCAV ü3200h R
0Fh RemCapMIX ü03E8h R
10h FullCAP ü ü 07D0h R/W
11h TTE ü0000h R
12h QResidual 00 ü ü 1E2Fh R/W
13h FullSOCThr ü4600h R/W
14h–15h RESERVED — —
16h AverageTemperature ü1600h R
17h Cycles ü ü 0000h R/W
18h DesignCap ü07D0h R/W
19h AverageVCELL üB400h R
1Ah MaxMinTemperature ü807Fh R/W
1Bh MaxMinVCELL ü00FFh R/W
1Ch MaxMinCurrent ü807Fh R/W
1Dh CONFIG ü2350h R/W
1Eh ICHGTerm ü03C0h R/W
1Fh RemCapAV ü03E8h R
20h RESERVED — —
21h Version ü00ACh R
MSB—ADDRESS 2Dh LSB—ADDRESS 2Dh
S 27262524232221202-1 2-2 2-3 2-4 2-5 2-6 2-7
MSb LSb MSb LSb
2-7 UNITS: +0.0078NC
43Maxim Integrated
MAX17047/MAX17050
ModelGauge m3 Fuel Gauge
Table 5. Device Memory Map (continued)
ADDRESS
(HEX) REGISTER NAME A/D
MEASURE
ALERT/
STATUS
MG m3
APP
DATA
MG m3
CELL
DATA
MG m3
CONFIG
MG m3
SAVE AND
RESTORE
MG m3
OUTPUT
POR
VALUE
READ/
WRITE
22h QResidual 10 ü ü 1E00h R/W
23h FullCapNom ü ü 07D0h R/W
24h TempNom ü1400h R/W
25h TempLim ü2305h R/W
26h RESERVED — —
27h AIN ü88D0h R
28h LearnCFG ü2602h R/W
29h FilterCFG ü4EA4h R/W
2Ah RelaxCFG ü203Bh R/W
2Bh MiscCFG ü0870h R/W
2Ch TGAIN üE3E1h R/W
2Dh TOFF ü290Eh R/W
2Eh CGAIN ü4000h R/W
2Fh COFF ü0000h R/W
30h–31h RESERVED — —
32h QResidual 20 ü ü 1306h R/W
33h–35h RESERVED — —
36h Iavg_empty ü0780h R/W
37h FCTC ü05E0h R/W
38h RCOMP0 ü ü 004Bh R/W
39h TempCo ü ü 262Bh R/W
3Ah V_empty ü9C5Ch R/W
3Bh RESERVED — —
3Ch RESERVED — —
3Dh FSTAT ü0001h R
3Eh TIMER ü0000h R
3Fh SHDNTIMER üE000h R/W
40h–41h RESERVED — —
42h QResidual 30 ü ü 0C00h R/W
43h–44h RESERVED — —
45h dQacc ü007Dh R/W
46h dPacc ü0C80h R/W
47h–4Ch RESERVED — —
4Dh QH ü0000h R/W
4Eh–7Fh RESERVED — —
80h–AFh Characterization
Table üN/A R/W
B0h–FAh RESERVED — —
FBh VFOCV ü0000h R
FCh–FEh RESERVED — —
FFh SOCVF ü0000h R
44Maxim Integrated
MAX17047/MAX17050
ModelGauge m3 Fuel Gauge
2-Wire Bus System
The 2-wire bus system supports operation as a slave-
only device in a single or multislave, and single or
multimaster system. Up to 128 slave devices may share
the bus by uniquely setting the 7-bit slave address. The
2-wire interface consists of a serial data line (SDA) and
serial clock line (SCL). SDA and SCL provide bidirec-
tional communication between the IC (slave device) and
a master device at speeds up to 400kHz. The device’s
SDA pin operates bidirectionally, that is, when the device
receives data, SDA operates as an input, and when the
device returns data, SDA operates as an open-drain out-
put, with the host system providing a resistive pullup. The
device always operates as a slave device, receiving and
transmitting data under the control of a master device.
The master initiates all transactions on the bus and gen-
erates the SCL signal, as well as the START and STOP
bits, which begin and end each transaction.
Bit Transfer
One data bit is transferred during each SCL clock cycle,
with the cycle defined by SCL transitioning low to high
and then high to low. The SDA logic level must remain
stable during the high period of the SCL clock pulse.
Any change in SDA when SCL is high is interpreted as a
START or STOP control signal.
Bus Idle
The bus is defined to be idle, or not busy, when no mas-
ter device has control. Both SDA and SCL remain high
when the bus is idle. The STOP condition is the proper
method to return the bus to the idle state.
START and STOP Conditions
The master initiates transactions with a START condition
(S), by forcing a high-to-low transition on SDA while SCL
is high. The master terminates a transaction with a STOP
condition (P), a low-to-high transition on SDA while SCL
is high. A Repeated START condition (Sr) can be used
in place of a STOP then START sequence to terminate
one transaction and begin another without returning the
bus to the idle state. In multimaster systems, a Repeated
START allows the master to retain control of the bus. The
START and STOP conditions are the only bus activities in
which the SDA transitions when SCL is high.
Acknowledge Bits
Each byte of a data transfer is acknowledged with an
Acknowledge bit (A) or a No Acknowledge bit (N). Both
the master and the device slave generate acknowledge
bits. To generate an Acknowledge, the receiving device
must pull SDA low before the rising edge of the acknowl-
edge-related clock pulse (ninth pulse) and keep it low
until SCL returns low. To generate a No Acknowledge
(also called NACK), the receiver releases SDA before
the rising edge of the acknowledge-related clock pulse
and leaves SDA high until SCL returns low. Monitoring
the acknowledge bits allows for detection of unsuccess-
ful data transfers. An unsuccessful data transfer can
occur if a receiving device is busy or if a system fault has
occurred. In the event of an unsuccessful data transfer,
the bus master should reattempt communication.
Data Order
A byte of data consists of 8 bits ordered most significant
bit (MSb) first. The least significant bit (LSb) of each byte
is followed by the Acknowledge bit. Device registers
composed of multibyte values are ordered least signifi-
cant byte (LSB) first.
Slave Address
A bus master initiates communication with a slave device
by issuing a START condition followed by a Slave Address
(SAddr) and the read/write (R/W) bit. When the bus is idle,
the device continuously monitors for a START condition
followed by its slave address. When the device receives a
slave address that matches the value in its Programmable
Slave Address register, it responds with an Acknowledge
bit during the clock period following the R/W bit. The 7-bit
Programmable Slave Address register is factory pro-
grammed and cannot be changed by the user.
IC SLAVE ADDRESS 0110110
Read/Write Bit
The R/W bit following the slave address determines the
data direction of subsequent bytes in the transfer. R/W
= 0 selects a write transaction, with the following bytes
being written by the master to the slave. R/W = 1 selects
a read transaction, with the following bytes being read
from the slave by the master.
Bus Timing
The device is compatible with any bus timing up to
400kHz. No special configuration is required to operate
at any speed.
2-Wire Command Protocols
The command protocols involve several transaction
formats. The simplest format consists of the master
writing the START bit, slave address, R/W bit, and then
45Maxim Integrated
MAX17047/MAX17050
ModelGauge m3 Fuel Gauge
Table 6. 2-Wire Protocol Key
monitoring the acknowledge bit for presence of the
device. More complex formats such as the write Data,
read Data, and Function command protocols write data,
read data, and execute device-specific operations,
respectively. All bytes in each command format require
the slave or the host system to return an Acknowledge bit
before continuing with the next byte. Each function com-
mand definition outlines the required transaction format.
Table 6 applies to the transaction formats.
Basic Transaction Formats
Write: S SAddr W A MAddr A DataL A DataH A P
A write transaction transfers 1 or more data bytes to the
device. The data transfer begins at the memory address
supplied in the MAddr byte. Control of the SDA signal is
retained by the master throughout the transaction, except
for the Acknowledge cycles.
Read: S SAddr W A MAddr A Sr SAddr R A DataL A DataH N P
write Portion read Portion
A read transaction transfers one or more words from the
IC. Read transactions are composed of two parts, a write
portion followed by a read portion, and are therefore
inherently longer than a write transaction. The write por-
tion communicates the starting point for the read opera-
tion. The read portion follows immediately, beginning with
a Repeated START, Slave Address with R/W set to a 1.
Control of SDA is assumed by the IC beginning with the
Slave Address Acknowledge cycle. Control of the SDA
signal is retained by the device throughout the transac-
tion, except for the Acknowledge cycles. The master
indicates the end of a read transaction by responding
to the last byte it requires with a No Acknowledge. This
signals the device that control of SDA is to remain with
the master following the Acknowledge clock.
Write Data Protocol
The write Data protocol is used to write to register and
shadow RAM data to the IC starting at memory address
MAddr. Data0 represents the data written to MAddr,
Data1 represents the data written to MAddr + 1, and
DataN represents the last data byte written to MAddr +
N. The master indicates the end of a write transaction by
sending a STOP or Repeated START after receiving the
last acknowledge bit:
S SAddr W A MAddr A DataL0 A DataH0 A DataL1
A DataH1 A … DataLN A DataHN A P
The MSb of the data to be stored at address MAddr
can be written immediately after the MAddr byte is
acknowledged. Because the address is automatically
incremented after the least significant bit (LSb) of each
byte is received by the device, the MSb of the data at
address MAddr + 1 can be written immediately after the
acknowledgment of the data at address MAddr. If the
bus master continues an autoincremented write transac-
tion beyond address FFh, the device ignores the data.
Data is also ignored on writes to read-only addresses
but not reserved addresses. Do not write to reserved
address locations.
Read Data Protocol
The read data protocol is used to read register and
shadow RAM data from the device starting at memory
address specified by MAddr. Data0 represents the data
byte in memory location MAddr, Data1 represents the
data from MAddr + 1, and DataN represents the last byte
read by the master:
S SAddr W A MAddr A Sr SAddr R A DataL0 A
DataH0 A DataL1 A DataH1 A …DataLN N DataHN N P
Data is returned beginning with the most significant bit
(MSb) of the data in MAddr. Because the address is
automatically incremented after the LSb of each byte
is returned, the MSb of the data at address MAddr +
1 is available to the host system immediately after the
acknowledgment of the data at address MAddr. If the
bus master continues to read beyond address FFh, the
device outputs data values of FFh. Addresses labeled
Reserved in the memory map return undefined data. The
bus master terminates the read transaction at any byte
boundary by issuing a No Acknowledge followed by a
STOP or Repeated START.
KEY DESCRIPTION KEY DESCRIPTION
SSTART bit Sr Repeated START
SAddr Slave Address
(7 bit) WR/W bit = 0
FCmd Function Command
byte RR/W bit = 1
MAddr Memory Address
byte PSTOP bit
Data Data byte written by
Master Data Data byte returned
by Slave
AAcknowledge bit—
Master AAcknowledge bit—
Slave
NNo Acknowledge—
Master NNo Acknowledge—
Slave
46Maxim Integrated
MAX17047/MAX17050
ModelGauge m3 Fuel Gauge
Package Information
For the latest package outline information and land patterns (foot-
prints), go to www.maximintegrated.com/packages. Note that a
“+”, “#”, or “-” in the package code indicates RoHS status only.
Package drawings may show a different suffix character, but the
drawing pertains to the package regardless of RoHS status.
Ordering Information
+Denotes a lead(Pb)-free/RoHS-compliant package.
T = Tape and reel.
*EP = Exposed pad.
PART TEMP RANGE PIN-PACKAGE
MAX17047G+ -40°C to +85°C 10 TDFN-EP*
MAX17047G+T10 -40°C to +85°C 10 TDFN-EP*
MAX17050X+ -40°C to +85°C 9 WLP
MAX17050X+T10 -40°C to +85°C 9 WLP
PACKAGE
TYPE
PACKAGE
CODE
OUTLINE
NO.
LAND
PATTERN
NO.
10 TDFN-EP T1033+1 21-0137 90-0003
9 WLP W91G1+1 21-0459
Refer to
Application
Note 1891
Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are implied.
Maxim reserves the right to change the circuitry and specifications without notice at any time. The parametric values (min and max limits) shown in the Electrical
Characteristics table are guaranteed. Other parametric values quoted in this data sheet are provided for guidance.
Maxim Integrated 160 Rio Robles, San Jose, CA 95134 USA 1-408-601-1000 47
© 2012 Maxim Integrated The Maxim logo and Maxim Integrated are trademarks of Maxim Integrated Products, Inc.
MAX17047/MAX17050
ModelGauge m3 Fuel Gauge
Revision History
REVISION
NUMBER
REVISION
DATE DESCRIPTION PAGES
CHANGED
0 9/11 Initial release —
1 12/11
Added MAX17050 and added multicell application circuit information, updated
schematics, Ordering Information, layout guideline, and Thermistor Sharing Circuit
section
1, 7, 8, 11–41,
43, 45
2 4/12 Corrected error on TDFN layout diagram in Figure 8 and corrected error of hard-
coded bits of the LearnCFG register 14, 25, 43
3 8/12
Corrected error with FullSOCThr register formatting in Figure 25; corrected error with
TOFF register formatting in Figure 62; added clarification that ALRTp bit must equal
0 to enable fast detection of cell removal
20, 30, 34, 42
