GG25L [STMICROELECTRONICS]
Fitness and healthcare;
ST 
GG25L
Gas gauge IC with alarm output
Datasheet - production data
Applications
Wearable
Fitness and healthcare
Portable medical equipment
Description
The GG25L includes the hardware functions
required to implement a low-cost gas gauge for
battery monitoring. The GG25L uses current
sensing, Coulomb counting and accurate
measurements of the battery voltage to estimate
the state-of-charge (SOC) of the battery. An
internal temperature sensor simplifies
CSP (1.4 x 2.0 mm)
Features
implementation of temperature compensation.
TM
OptimGauge algorithm
An alarm output signals a low SOC condition and
can also indicate low battery voltage. The alarm
threshold levels are programmable.
0.25% accuracy battery voltage monitoring
Coulomb counter and voltage-mode gas gauge
operations
The GG25L offers advanced features to ensure
high performance gas gauging in all application
conditions.
Robust initial open-circuit-voltage (OCV)
measurement at power up with debounce
delay
Low battery level alarm output with
programmable thresholds
Internal temperature sensor
Battery swap detection
Low power: 45 µA in power-saving mode, 2 µA
max in standby mode
1.4 x 2.0 mm 10-bump CSP package
Table 1. Device summary
Temperature range Package
Order code
Packing
Marking
GG25LJ (1)
O22
O23
-40 °C to +85 °C
CSP-12
Tape and reel
GG25LAJ (2)
1. 4.35 V battery option
2. 4.20 V battery option
February 2014
DocID025995 Rev 1
1/28
This is information on a product in full production.
www.st.com
Contents
GG25L
Contents
1
2
3
4
5
6
Block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
Pin assignment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
Absolute maximum ratings and operating conditions . . . . . . . . . . . . . 4
Electrical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Application information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
6.1
Battery monitoring functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
6.1.1
6.1.2
6.1.3
6.1.4
Operating modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Battery voltage monitoring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Internal temperature monitoring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
Current sensing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
6.2
GG25L gas gauge architecture . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
6.2.1
6.2.2
6.2.3
Coulomb counter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Voltage gas gauge algorithm . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Mixed mode gas gauge system . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
6.3
6.4
6.5
Low battery alarm . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
Power-up and battery swap detection . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
Improving accuracy of the initial OCV measurement with
the advanced functions of BATD/CD and RSTIO pins . . . . . . . . . . . . . . . 17
6.5.1
BATD and RSTIO pins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
7
I²C interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
7.1
7.2
Read and write operations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
Register map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
7.2.1
7.2.2
Register map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
Register description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
8
9
Package information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
2/28
DocID025995 Rev 1
GG25L
Block diagram
1
Block diagram
Figure 1. GG25L internal block diagram
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Pin assignment
GG25L
2
Pin assignment
Table 2. GG25L pin description
Pin
n°
CSP
bump
Pin name
Type(1)
Function
Alarm signal output, open drain,
external pull-up with resistor
1
A1
ALM
I/OD
2
3
4
5
6
7
B1
C1
D1
D2
D3
C3
SDA
SCL
GND
NC
I/OD
I_D
I²C serial data
I²C serial clock
Ground Analog and digital ground
-
NC
CG
I_A
I/OD
Current sensing input
RSTIO
Reset sense input & reset control output (open drain)
Battery charge inhibit (active high output)
Battery detection (input)
8
B2
BATD/CD
I/OA
9
B3
A3
VCC
VIN
Supply Power supply
I_A Battery voltage sensing input
10
1. I = input, 0 = output, OD = open drain, A = analog, D = digital, NC = not connected
3
Absolute maximum ratings and operating conditions
Table 3. Absolute maximum ratings
Symbol
Parameter
Value
Unit
VCCMAX
VIO
TSTG
TJ
Maximum voltage on VCC pin
Voltage on I/O pins
6
-0.3 to 6
-55 to 150
150
V
Storage temperature
°C
kV
Maximum junction temperature
Electrostatic discharge (HBM: human body model)
ESD
2
Table 4. Operating conditions
Parameter
Symbol
Value
Unit
VCC
VMIN
Operating supply voltage on VCC
2.7 to 4.5
2.0
V
Minimum voltage on VCC for RAM content retention
TOPER
TPERF
-40 to 85
-20 to 70
Operating free air temperature range
°C
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GG25L
Electrical characteristics
4
Electrical characteristics
Table 5. Electrical characteristics (2.7 V < V < 4.5 V, -20C to 70C)
CC
Symbol
Parameter
Conditions
Min
Typ
Max Units
Supply
Average value over 4 s in
power-saving voltage
mode
45
60
ICC
Operating current consumption
Average value over 4 s in
mixed mode
100
µA
Standby mode,
inputs = 0 V
ISTBY
IPDN
Current consumption in standby
2
1
VCC < UVLOTH,
inputs = 0 V
Current consumption in power-down
UVLOTH
UVLOHYST
POR
Undervoltage threshold
(VCC decreasing)
(VCC decreasing)
2.5
2.6
100
2.0
2.7
V
mV
V
Undervoltage threshold hysteresis
Power-on reset threshold
Current sensing
Vin_gg
Input voltage range
-40
-3
+40
500
mV
nA
IIN
Input current for CG pin
AD converter granularity
AD converter offset
ADC_res
ADC_offset
ADC_time
5.88
µV
CG = 0 V
3
1
LSB
ms
AD conversion time
500
0.5
25 °C
AD converter gain accuracy at full
scale (using external sense resistor)
ADC_acc
FOSC
%
Over temperature range
Internal time base frequency
Internal time base accuracy
Current register LSB value
32768
2
Hz
25 °C, VCC = 3.6 V
Osc_acc
Cur_res
%
Over temperature and
voltage ranges
2.5
5.88
µV
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Electrical characteristics
GG25L
Table 5. Electrical characteristics (2.7 V < V < 4.5 V, -20C to 70C) (continued)
CC
Symbol
Parameter
Conditions
Min
Typ
Max Units
Battery voltage and temperature measurement
Vin_adc
LSB
Input voltage range
LSB value
V
CC = 4.5 V
0
4.5
V
Voltage measurement
2.20
1
mV
°C
Temperature measurement
ADC_time
AD conversion time
250
ms
2.7 V < Vin < 4.5 V,
-0.25
+0.25
VCC = Vin 25 °C
Volt_acc
Battery voltage measurement accuracy
%
Over temperature range
-0.5
-3
+0.5
3
Temp_acc
Internal temperature sensor accuracy
°C
Digital I/O pins (SCL, SDA, ALM, RSTIO)
Vih
Input logic high
1.2
Vil
Input logic low
0.35
0.4
V
V
Vol
Output logic low (SDA, ALM, RSTIO)
Iol = 4 mA
BATD/CD pin
Vith
Input threshold voltage
Input voltage hysteresis
1.46 1.61 1.76
0.1
Vihyst
Output logic high
(charge inhibit mode enable)
Vbat-
0.4
Voh
Ioh = 3 mA
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Electrical characteristics
Table 6. I²C timing - V = 2.8 V, T
= -20 °C to 70 C (unless otherwise specified)
IO
amb
Symbol
Fscl
thd,sta
tlow
Parameter
SCL clock frequency
Min
Typ
Max
Unit
0
400
kHz
Hold time (repeated) START condition
LOW period of the SCL clock
HIGH period of the SCL clock
Setup time for repeated START condition
Data hold time
0.6
1.3
0.6
0.6
0
thigh
µs
tsu,dat
thd,dat
tsu,dat
0.9
Data setup time
100
ns
ns
-
20+
0.1Cb
tr
Rise time of both SDA and SCL signals
300
300
20+
0.1Cb
tf
Fall time of both SDA and SCL signals
Setup time for STOP condition
ns
µs
µs
pF
tsu,sto
tbuf
Cb
0.6
1.3
Bus free time between a STOP and
START condition
Capacitive load for each bus line
400
Figure 2. I²C timing diagram
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Application information
GG25L
5
Application information
Figure 3. Example of an application schematic using the GG25L in mixed mode
Optional filter
IO voltage
VCC
VIN
C1
R1
C2
Other
detection
circuit
SCL
SDA
GG25L
Battery pack
BATD/CD
CG
ALM
R2
Rid
RSTIO
GND
Rcg
Table 7. External component list
Tolerance Comments
Name
Value
Rcg
C1
C2
R1
R2
5 to 50 mΩ
1 µF
1% to 5% Current sense resistor (2% or better recommended)
Supply decoupling capacitor
220 nF
1 kΩ
Battery voltage input filter (optional)
Battery voltage input filter (optional)
Battery detection function
1 kΩ
Figure 4. Example of an application schematic using the GG25L without current
sensing
Optional filter
IO voltage
VCC
R1
C2
C1
Other
detection
circuit
VIN
SCL
SDA
GG25L
Battery pack
BATD/CD
ALM
R2
Rid
RSTIO
CG
GND
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GG25L
Application information
Table 8. External component list
Comments
Name
Value
C1
C2
R1
R2
1 µF
220 nF
1 kΩ
Supply decoupling capacitor
Battery voltage input filter (optional)
Battery detection function
1 kΩ
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Functional description
GG25L
6
Functional description
6.1
Battery monitoring functions
6.1.1
Operating modes
The monitoring functions include the measurement of battery voltage, current, and
temperature. A Coulomb counter is available to track the SOC when the battery is charging
or discharging at a high rate. A sigma-delta A/D converter is used to measure the voltage,
current, and temperature.
The GG25L can operate in two different modes with different power consumption (see
Table 9. Mode selection is made by the VMODE bit in register 0 (refer to Table 14 for
register 0 definition).
Table 9. GG25L operating modes
VMODE
Description
0
Mixed mode, Coulomb counter is active, voltage gas gauge runs in parallel
Voltage gas gauge with power saving
1
Coulomb counter is not used. No current sensing.
In mixed mode, current is measured continuously (except for a conversion cycle every 4 s
and every 16 s seconds for measuring voltage and temperature respectively). This provides
the highest accuracy from the gas gauge.
In voltage mode with no current sensing, a voltage conversion is made every 4 s and a
temperature conversion every 16 s. This mode provides the lowest power consumption.
It is possible to switch between the two operating modes to get the best accuracy during
active periods, and to save power during standby periods while still keeping track of the
SOC information.
6.1.2
Battery voltage monitoring
Battery voltage is measured by using one conversion cycle of the A/D converter every 4 s.
13
The conversion cycle takes 2 = 8192 clock cycles. Using the 32768 Hz internal clock, the
conversion cycle time is 250 ms.
The voltage range is 0 to 4.5 V and resolution is 2.20 mV. Accuracy of the voltage
measurement is ±0.5% over the temperature range. This allows accurate SOC information
from the battery open-circuit voltage.
The result is stored in the REG_VOLTAGE register (see Table 13).
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GG25L
Functional description
6.1.3
Internal temperature monitoring
The chip temperature (close to the battery temperature) is measured using one conversion
cycle of the A/D converter every 16 s.
13
The conversion cycle takes 2 = 8192 clock cycles. Using the 32768 Hz internal clock, the
conversion cycle time is 250 ms. Resolution is 1° C and range is -40 to +125 °C.
The result is stored in the REG_TEMPERATURE register (see Table 13).
6.1.4
Current sensing
Voltage drop across the sense resistor is integrated during a conversion period and input to
the 14-bit sigma-delta A/D converter.
Using the 32768 Hz internal clock, the conversion cycle time is 500 ms for a 14-bit
resolution. The LSB value is 5.88 µV. The A/D converter output is in two’s complement
format.
When a conversion cycle is completed, the result is added to the Coulomb counter
accumulator and the number of conversions is incremented in a 16-bit counter.
The current register is updated only after the conversion closest to the voltage conversion
(that is: once per 4-s measurement cycle). The result is stored in the REG_CURRENT
register (see Table 13).
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Functional description
GG25L
6.2
GG25L gas gauge architecture
6.2.1
Coulomb counter
The Coulomb counter is used to track the SOC of the battery when the battery is charging or
discharging at a high rate. Each current conversion result is accumulated (Coulomb
counting) for the calculation of the relative SOC value based on the configuration register.
The system controller can control the Coulomb counter and set and read the SOC register
through the I²C control registers.
Figure 5. Coulomb counter block diagram
REG_COUNTER
register
16-bit counter
REG_CURRENT
register
EOC
CC SOC
register (internal)
CC SOC
calculator
CG
AD converter
GND
REG_CC_CNF
register
The REG_CC_CNF value depends on battery capacity and the current sense resistor. It
scales the charge integrated by the sigma delta converter into a percentage value of the
battery capacity. The default value is 395 (corresponding to a 10 mΩ sense resistor and
1957 mAh battery capacity).
The Coulomb counter is inactive if the VMODE bit is set, this is the default state at power-
on-reset (POR) or reset (VMODE bit = 1).
Writing a value to the register REG_SOC (mixed mode SOC) forces the Coulomb counter
gas gauge algorithm to restart from this new SOC value.
REG_CC_CNF register is a 16-bit integer value and is calculated as shown in Equation 1:
Equation 1
REG_CC_CNF = Rsense Cnom 49.556
Rsense is in mΩ and Cnom is in mAh.
Example: Rsense =10 mΩ, Cnom = 1650 mAh, REG_CC_CNF = 333
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GG25L
Functional description
6.2.2
Voltage gas gauge algorithm
No current sensing is needed for the voltage gas gauge. An internal algorithm precisely
simulates the dynamic behavior of the battery and provides an estimation of the OCV. The
battery SOC is related to the OCV by means of a high-precision reference OCV curve built
into the GG25L.
Any change in battery voltage causes the algorithm to track both the OCV and SOC values,
taking into account the non-linear characteristics and time constants related to the chemical
nature of the Li-Ion and Li-Po batteries.
A single parameter fits the algorithm to a specific battery. The default value provides good
results for most battery chemistries used in hand-held applications.
Figure 6. Voltage gas gauge block diagram
Voltage register
VM configuration
VIN
AD
converter
OCV value
Voltage mode
(VM)
algorithm
To SOC
management
Reference
OCV
curve
OCV adjustment registers
Voltage gas gauge algorithm registers
The REG_VM_CNF configuration register is used to configure the parameter used by the
algorithm based on battery characteristic. The default value is 321.
The REG_OCV register holds the estimated OCV value corresponding to the present
battery state.
The REG_OCVTAB registers are used to adjust the internal OCV table to a given battery
type.
The REG_VM_CNF register is a 12-bit integer value and is calculated from the averaged
internal resistance and nominal capacity of the battery as shown in Equation 2:
Equation 2
REG_VM_CNF = Ri Cnom 977.78
Ri is in mΩ and Cnom is in mAh.
Example: Ri = 190 mΩ, Cnom =1650 mAh, REG_VM_CNF = 321
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Functional description
GG25L
6.2.3
Mixed mode gas gauge system
The GG25L provides a mixed mode gas gauge using both a Coulomb counter (CC) and a
voltage-mode (VM) algorithm to track the SOC of the battery in all conditions with optimum
accuracy. The GG25L directly provides the SOC information.
The Coulomb counter is mainly used when the battery is charging or discharging at a high
rate. Each current conversion result is accumulated (Coulomb counting) for the calculation
of the relative SOC value based on a configuration register.
The voltage-mode algorithm is used when the application is in low power consumption state.
The GG25L automatically uses the best method in any given application condition.
However, when the application enters standby mode, the GG25L can be put in power-
saving mode: only the voltage-mode gas gauge stays active, the Coulomb counter is
stopped and power consumption is reduced.
Figure 7. Mixed mode gas gauge block diagram
Voltage mode
gas gauge
(VM)
SOC
management
REG_SOC
register
Coulomb
counter
(CC)
Alarm
management
REG_VM_ADJ
register
Parameter
tracking
REG_CC_ADJ
register
The combination of the CC and VM algorithms provides optimum accuracy under all
application conditions. The voltage gas gauge cancels any long-term errors and prevents
the SOC drift problem that is commonly found in Coulomb counter only solutions.
Furthermore, the results of the two algorithms are continuously compared and adjustment
factors are calculated. This enables the application to track the CC and VM algorithm
parameters for long-term accuracy, automatically compensating for battery aging,
application condition changes, and temperature effects. Five registers are dedicated to this
monitoring:
REG_CC_ADJ and REG_VM_ADJ are continuously updated. They are signed, 16-bit,
user-adjusted registers with LSB = 1/512 %.
ACC_CC_ADJ and ACC_VM_ADJ are updated only when a method switch occurs.
They are signed, 16-bit user adjusted accumulators with LSB = 1/512%
RST_ACC_CC_ADJ and RST_ACC_VM_ADJ bits in the REG_MODE register are
used to clear the associated counter.
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Functional description
6.3
Low battery alarm
The ALM pin provides an alarm signal in case of a low battery condition. The output is an
open drain and an external pull-up resistor is needed in the application. Writing the
IO0DATA bit to 0 forces the ALM output low; writing the IO0DATA bit to 1 lets the ALM
output reflect the battery condition. Reading the IO0DATA bit gives the state of the ALM pin.
When the IO0DATA bit is 1, the ALM pin is driven low if either of the following two conditions
is met:
The battery SOC estimation from the mixed algorithm is less than the programmed
threshold (if the alarm function is enabled by the ALM_ENA bit).
The battery voltage is less than the programmed low voltage level (if the ALM_ENA bit
is set).
When a low-voltage or low-SOC condition is triggered, the GG25L drives the ALM pin low
and sets the ALM_VOLT or ALM_SOC bit in REG_CTRL.
The ALM pin remains low (even if the conditions disappear) until the software writes the
ALM_VOLT and ALM_SOC bits to 0 to clear the interrupt.
Clearing the ALM_VOLT or ALM_SOC while the corresponding low-voltage or low-SOC
condition is still in progress does not generate another interrupt; this condition must
disappear first and must be detected again before another interrupt (ALM pin driven low) is
generated for this alarm. Another alarm condition, if not yet triggered, can still generate an
interrupt.
Usually, the low-SOC alarm occurs first to warn the application of a low battery condition,
then if no action is taken and the battery discharges further, the low-voltage alarm signals a
nearly-empty battery condition.
At power-up, or when the GG25L is reset, the SOC and voltage alarms are enabled
(ALM_ENA bit = 1). The ALM pin is high-impedance directly after POR and is driven low if
the SOC and/or the voltage is below the default thresholds (1% SOC, 3.00 V voltage), after
the first OCV measurement and SOC estimation.
The REG_SOC_ALM register holds the relative SOC alarm level in 0.5 % units (0 to 100 %).
Default value is 2 (i.e. 1% SOC).
The REG_ALARM_VOLTAGE holds the low voltage threshold and can be programmed over
the full scale voltage range with 17.60 (2.20 * 8) mV steps. The default value is 170 (3.00 V).
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Functional description
GG25L
6.4
Power-up and battery swap detection
When the GG25L is powered up at first battery insertion, an automatic battery voltage
measurement cycle is made immediately after startup and debounce delay.
This feature enables the system controller to get the SOC of a newly inserted battery based
on the OCV measured just before the system actually starts.
Figure 8. Timing diagram at power-up
A battery swap is detected when the battery voltage drops below the undervoltage lockout
(UVLO) for more than 1 s. The GG25L restarts when the voltage goes back above UVLO, in
the same way as for a power-up sequence.
Such filtering provides robust battery swap detection and prevents restarting in case of short
voltage drops. This feature protects the application against high surge currents at low
temperatures.
Figure 9. Restart in case of battery swap
<1s
>1s
VCC
UVLO
POR
Short UVLO
event < 1s
No restart,
No operation
interuption
Long battery disconnection
events > 1s
GG25L restarts
GAMS2502141520SG
Example: When BATD/CD is high (voltage above the 1.61 V threshold) for more than 1 s, a
battery swap is detected. The GG25L restarts when the BATD/CD level returns below the
threshold, in the same way as for a power-up sequence.
Using the 1-s filter prevents false battery swap detection if short contact bouncing occurs at
the battery terminals due to mechanical vibrations or shocks.
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GG25L
Functional description
6.5
Improving accuracy of the initial OCV measurement with the
advanced functions of BATD/CD and RSTIO pins
The advanced functions of the BATD/CD and RSTIO pins provide a way to ensure that the
OCV measurement at power-up is not affected by the application startup or by the charger
operation. This occurs as follows:
The BATD/CD pin is driven high to V voltage which inhibits the charge function
(assuming that the BATD/CD signal is connected to disable input of the charger circuit).
CC
The RSTIO pin senses the system reset state and if the system reset is active (that is
RSTIO is low), the RSTIO is kept low until the end of the OCV measurement.
Figure 10 describes the BATD/CD and RSTIO operation at power-up. Please refer to the
block diagram of Figure 11 for the RSTI, RSTO, BATD_comp_out, and BATD_drive_high
signals.
At the end of the OCV measurement, the BATD/CD and RSTIO pin are released (high
impedance), the application can start and the charger is enabled.
Figure 10. BATD and RSTIO timing diagram at power-up
SOC
calc.
Application can start,
charge is enabled
OCV
meas.
delay
VCC
UVLO
POR
1.61V
BATD_comp_out
BATD_drive_high
RSTI
RST0
Voltage
measurement
Voltage
register
SOC register
6.5.1
BATD and RSTIO pins
The GG25L provides platform synchronization signals to provide reliable SOC information in
different cases.
The BATD/CD pin senses the presence of the battery independently of the battery voltage
and it controls the battery charger to inhibit the charge during the initial OCV measurement.
The RSTIO pin can be used to delay the platform startup during the first OCV measurement
at battery insertion.
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Functional description
GG25L
Figure 11. BATD and RSTIO
VCC
BATD_drive_high
BATD/CD
+
-
BATD_comp_out
1.61 V
RSTIO
RSTI
RSTO
The BATD/CD pin used as a battery detector is an analog I/O.The input detection threshold
is typically 1.61 V.
BATD/CD is also an output connected to V level when active. Otherwise, it is high
CC
impedance.
The RSTIO signal is used to control the application system reset during the initial OCV
measurement. The RSTIO pin is a standard I/O pin with open drain output.
BATD/CD can be connected to the NTC sensor or to the identification resistor of the battery
pack. The GG25L does not provide any biasing voltage or current for the battery detection.
An external pull-up resistor or another device has to pull the BATD/CD pin high when the
battery is removed.
Figure 12. BATD/CD pin connection when used as battery detector
Other biasing
and/or detection
circuit
GG25L
GG25L
(>1 M)
Ru
Battery
pack
Battery pack
BATD/CD
BATD/CD
1K
1K
Rid
Rid
BATD resistor biasing
BATD biasing by external circuitry
18/28
DocID025995 Rev 1
GG25L
I²C interface
7
I²C interface
7.1
Read and write operations
The I²C interface is used to control and read the current accumulator and registers. It is
compatible with the Philips I²C Bus® (version 2.1). It is a slave serial interface with a serial
data line (SDA) and a serial clock line (SCL).
SCL: input clock used to shift data
SDA: input/output bidirectional data transfers
A filter rejects the potential spikes on the bus data line to preserve data integrity.
The bidirectional data line supports transfers up to 400 Kbit/s (fast mode). The data are
shifted to and from the chip on the SDA line, MSB first.
The first bit must be high (START) followed by the 7-bit device address and the read/write
control bit. Bits DevADDR0 to DevADDR2 are factory-programmable, the default device
address value being 1110 000 (AddrID0 = AddrID1 = AddrID2 = 0). The GG25L then sends
an acknowledge at the end of an 8-bit long sequence. The next eight bits correspond to the
register address followed by another acknowledge.
The data field is the last 8-bit long sequence sent, followed by a last acknowledge.
Table 10. Device address format
bit7
bit6
bit5
bit4
bit3
bit2
bit1
bit0
1
1
1
0
DevADDR2 DevADDR1 DevADDR0
R/W
Table 11. Register address format
bit5 bit4 bit3 bit2
bit7
bit6
bit1
bit0
RegADDR7 RegADDR6 RegADDR5 RegADDR4 RegADDR3 RegADDR2 RegADDR1 RegADDR0
Table 12. Register data format
bit7
bit6
bit5
bit4
bit3
bit2
bit1
bit0
DATA7
DATA6
DATA5
DATA4
DATA3
DATA2
DATA1
DATA0
DocID025995 Rev 1
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I²C interface
GG25L
Figure 13. Read operation
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GG25L
I²C interface
7.2
Register map
7.2.1
Register map
The register space provides 28 control registers, 1 read-only register for device ID, 16
read/write RAM working registers reserved for the gas gauge algorithm, and 16 OCV
adjustment registers. Mapping of all registers is shown in Table 13. Detailed descriptions of
registers 0 (REG_MODE) and 1 (REG_CTRL) are shown in Table 14 and Table 15. All
registers are reset to default values at power-on or reset, and the PORDET bit in register
REG_CTRL is used to indicate the occurrence of a power-on reset.
Table 13. Register map
Address
(decimal)
Soft
POR
Name
Type
POR
Description
LSB
Control registers
REG_MODE
REG_CTRL
0 to 23
0
1
R/W
R/W
R/W
Mode register
Control and status register
Gas gauge relative SOC
REG_SOC
2-3
1/512%
5.88 µV
Number of conversions
(2 bytes)
REG_COUNTER
REG_CURRENT
4-5
6-7
R
R
0x00
0x00
0x00
0x00
Battery current value
(2 bytes)
Battery voltage value
(2 bytes)
REG_VOLTAGE
8-9
10
11
R
R
0x00
0x00
0x00
0x00
0x00
0x00
2.2 mV
1 °C
REG_TEMPERATURE
REG_CC_ADJ_HIGH
Temperature data
Coulomb counter adjustment
factor
R/W
1/2%
Voltage mode adjustment
factor
REG_VM_ADJ_HIGH
REG_OCV
12
R/W
R/W
R/W
0x00
0x00
395
0x00
0x00
395
13-14
15-16
OCV register (2 bytes)
0.55 mV
Coulomb counter gas gauge
configuration
REG_CC_CNF
Voltage gas gauge algorithm
parameter
REG_VM_CNF
17-18
19
R/W
R/W
R/W
321
0x02
0xAA
321
0x02
0xAA
SOC alarm level
(default = 1%)
REG_ALARM_SOC
REG_ALARM_VOLTAGE
1/2%
Battery low voltage alarm
level (default is 3 V)
20
17.6 mV
47.04 µV
Current threshold for the
relaxation counter
REG_CURRENT_THRES
REG_RELAX_COUNT
REG_RELAX_MAX
REG_ID
21
22
23
24
R/W
R
0x0A
0x78
0x78
0x14
0x0A
0x78
0x78
0x14
Relaxation counter
Relaxation counter max
value
R/W
R
Part type ID = 14h
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I²C interface
GG25L
LSB
Table 13. Register map (continued)
Address
Soft
Name
Type
POR
Description
(decimal)
POR
Coulomb counter adjustment
factor
REG_CC_ADJ_LOW
REG_VM_ADJ_LOW
ACC_CC_ADJ
25
R/W
R/W
R/W
R/W
0x00
0x00
0x00
0x00
0x00
0x00
0x00
0x00
Voltage mode adjustment
factor
26
1/512%
Coulomb Counter correction
accumulator
27-28
Voltage mode correction
accumulator
ACC_VM_ADJ
RAM registers
REG_RAM0
...
29-30
32 to 47
32
Working register 0 for gas
gauge
R/W Random Unchanged
R/W Random Unchanged
...
...
Working register 15 for gas
gauge
REG_RAM15
47
OCV adjustment
registers
OCV adjustment table
(16 registers)
REG_OCVTAB
48 to 63
R/W
0x00
0x00
0.55 mV
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DocID025995 Rev 1
GG25L
I²C interface
7.2.2
Register description
Values held in consecutive registers (such as the charge value in the REG_SOC register
pair) are stored with high bits in the first register and low bits in the second register. The
registers must be read with a single I²C access to ensure data integrity. It is possible to read
multiple values in one I²C access. All values must be consistent.
The SOC data are coded in binary format and the LSB of the low byte is 1/512 %. The
battery current is coded in 2’s complement format and the LSB value is 5.88 µV. The battery
voltage is coded in 2’s complement format and the LSB value is 2.20 mV. The temperature
is coded in 2’s complement format and the LSB value is 1°C.
Table 14. REG_MODE - address 0
Name
Position Type
Def.
Description
0: Mixed mode (Coulomb counter active)
1: Power saving voltage mode
VMODE
0
1
2
3
R/W
R/W
R/W
R/W
1
Write 1 to clear ACC_VM_ADJ and
REG_VM_ADJ.
Auto clear bit if GG_RUN = 1
CLR_VM_ADJ
CLR_CC_ADJ
ALM_ENA
0
0
1
Write 1 to clear ACC_CC_ADJ and REG_CC_ADJ
Auto clear bit if GG_RUN = 1
Alarm function
0: Disabled
1: Enabled
0: Standby mode. Accumulator and counter
registers are frozen, gas gauge and battery
monitor functions are in standby.
1: Operating mode.
GG_RUN
FORCE_CC
FORCE_VM
4
5
R/W
R/W
R/W
0
0
0
Forces the mixed mode relaxation timer to switch
to the Coulomb counter mode.
Write 1, self clear to 0
Relaxation counter = 0
Forces the mixed mode relaxation timer to switch
to voltage gas gauge mode.
Write 1, self clear to 0
6
7
Relaxation counter = Relax_max
Unused
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I²C interface
GG25L
Table 15. REG_CTRL - address 1
Name
Position Type
Def.
Description
ALM pin status
0 = ALM input is low
1 = ALM input is high
R
W
X
IO0DATA
0
ALM pin output drive
0 = ALM is forced low
1 = ALM is driven by the alarm conditions
1
0
0
0
1
0: no effect
1: resets the conversion counter
GG_RST is a self-clearing bit.
GG_RST
GG_VM
BATFAIL
1
2
3
W
Voltage mode active
0 = REG_SOC from Coulomb counter mode
1 = REG_SOC from Voltage mode
R
Battery removal or UVLO detection bit.
Write 0 to clear
(Write 1 is ignored)
R/W
R
Power on reset (POR) detection bit
0 = no POR event occurred
1 = POR event occurred
Soft reset
PORDET
4
5
0 = release the soft-reset and clear the POR
detection bit,
1 = assert the soft-reset and set the POR detection
bit.
W
0
This bit is self clearing.
Set with a low-SOC condition.
Cleared by writing 0.
ALM_SOC
ALM_VOLT
R/W
R/W
0
0
Set with a low-voltage condition.
Cleared by writing 0.
6
7
Unused
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DocID025995 Rev 1
GG25L
Package information
8
Package information
In order to meet environmental requirements, ST offers these devices in different grades of
®
®
ECOPACK packages, depending on their level of environmental compliance. ECOPACK
specifications, grade definitions and product status are available at: www.st.com.
®
ECOPACK is an ST trademark.
Figure 15. Flip Chip CSP 1.40 x 2.04 mm package mechanical drawing
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1. The terminal A1 on the bump side is identified by a distinguishing feature - for instance, by a circular “clear
area” typically 0.1 mm in diameter and/or a missing bump.
2. The terminal A1, on the back side, is identified by a distinguishing feature - for instance, by a circular “clear
DocID025995 Rev 1
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Package information
GG25L
area” typically 0.2 mm in diameter depending on the die size.
Table 16. Flip Chip CSP 1.4 x 2.04 mm package mechanical data
Dimensions
Symbol
Millimeters
Typ.
Inches
Typ.
Min.
Max.
Min.
Max.
A
A1
A2
b
0.545
0.165
0.330
0.220
1.98
0.600
0.200
0.350
0.260
2.01
0.655
0.235
0.370
0.300
2.04
0.021
0.006
0.013
0.009
0.078
0.024
0.008
0.014
0.010
0.079
0.047
0.054
0.031
0.016
0.016
0.011
0.002
0.026
0.009
0.015
0.012
0.080
D
D1
E
1.20
1.34
1.37
1.40
0.053
0.055
E1
e
0.800
0.400
0.405
0.285
0.050
0.360
0.395
0.275
0.440
0.415
0.295
0.014
0.016
0.011
0.017
0.016
0.012
fD
fE
G
ccc
0.050
0.002
Figure 16. Flip Chip CSP 1.4 x 2.04 mm footprint recommendation
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Revision history
9
Revision history
Table 17. Document revision history
Changes
Date
Revision
28-Feb-2014
1
Initial release
DocID025995 Rev 1
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28
GG25L
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