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STC3115
Gas gauge IC with alarm output for handheld applications
Datasheet - production data
Applications
• Mobile phones, multimedia players, digital
cameras
• Portable medical equipment
Description
The STC3115 includes the hardware functions
required to implement a low-cost gas gauge for
battery monitoring. The STC3115 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
implementation of temperature compensation.
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An alarm output signals a low SOC condition and
can also indicate low battery voltage. The alarm
threshold levels are programmable.
The STC3115 offers advanced features to ensure
high performance gas gauging in all application
conditions.
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Features
• OptimGaugeTM algorithm
• 0.25% accuracy battery voltage monitoring
• Coulomb counter and voltage-mode gas gauge
operations
• Robust initial open-circuit-voltage (OCV)
measurement at power up
• Programmable low battery alarm
• Internal temperature sensor
• Battery swap detection
• Low power: 45 µA in power-saving mode, 2 µA
max in standby mode
• Micro-sized packages:
– 1.4 x 2.0 mm 10-bump CSP package
– 2.0 x 3.0 mm DFN10 package
December 2014
This is information on a product in full production.
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www.st.com
Contents
STC3115
Contents
1
Block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
2
Pin assignment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
3
Absolute maximum ratings and operating conditions . . . . . . . . . . . . . 6
4
Electrical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
5
Application information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
6
Functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
6.1
6.2
Battery monitoring functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
6.1.1
Operating modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
6.1.2
Battery voltage monitoring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
6.1.3
Internal temperature monitoring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
6.1.4
Current sensing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
STC3115 gas gauge architecture . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
6.2.1
Coulomb counter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
6.2.2
Voltage gas gauge algorithm . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
6.2.3
Mixed mode gas gauge system . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
6.3
Low battery alarm . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
6.4
Power-up and battery swap detection . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
6.5
Improving accuracy of the initial OCV measurement with the advanced
functions of BATD/CD and RSTIO/BATD pins . . . . . . . . . . . . . . . . . . . . . 19
6.5.1
7
8
I2C interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
7.1
Read and write operations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
7.2
Register map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
7.2.1
Register map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
7.2.2
Register description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
Package information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
8.1
2/34
BATD and RSTIO pins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
Flip Chip CSP 1.40 x 2.04 mm package information . . . . . . . . . . . . . . . . 28
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STC3115
Contents
8.2
DFN10 2.0 x 3.0 mm package mechanical data . . . . . . . . . . . . . . . . . . . 30
9
Ordering information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
10
Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
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Block diagram
1
STC3115
Block diagram
Figure 1. STC3115 internal block diagram
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STC3115
2
Pin assignment
Pin assignment
Table 1. STC3115 pin description
DFN
Pin
CSP
bump
Pin
name
Type(1)
1
A1
ALM
I/OD
Alarm signal output, open drain,
external pull-up with resistor
2
B1
SDA
I/OD
I2C serial data
3
C1
SCL
I_D
I2C serial clock
4
D2
NC
-
Not connected
5
D1
GND
Ground
6
D3
CG
I_A
Current sensing input
7
C3
RSTIO
I/OD
Reset sense input & reset control output (open drain)
8
B2
BATD/CD
I/OA
Battery charge inhibit (active high output)
Battery detection (input)
9
B3
VCC
Supply
10
A3
VIN
I_A
Function
Analog and digital ground
Power supply
Battery voltage sensing input
1. I = input, 0 = output, OD = open drain, A = analog, D = digital, NC = not connected
Figure 2. Pin connections for each package (top view)
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Absolute maximum ratings and operating conditions
3
STC3115
Absolute maximum ratings and operating conditions
Table 2. Absolute maximum ratings
Symbol
VCCMAX
VIO
TSTG
TJ
ESD
Parameter
Maximum voltage on VCC pin
Voltage on I/O pins
Value
6
-0.3 to 6
Storage temperature
-55 to 150
Maximum junction temperature
Electrostatic discharge (HBM: human body model)
150
Unit
V
°C
2
kV
Value
Unit
Table 3. Operating conditions
Symbol
VCC
Operating supply voltage on VCC
VMIN
Minimum voltage on VCC for RAM content retention
TOPER
TPERF
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Parameter
Operating free air temperature range
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2.7 to 4.5
2.0
-40 to 85
-20 to 70
V
°C
STC3115
4
Electrical characteristics
Electrical characteristics
Table 4. Electrical characteristics (2.7 V < VCC < 4.5 V, -20 ° C to 70 ° C)
Symbol
Parameter
Conditions
Min
Typ
Max
45
60
Units
Supply
ICC
Operating current consumption
Average value over 4 s in
power-saving voltage
mode
Average value over 4 s in
mixed mode
100
ISTBY
Current consumption in standby
Standby mode,
inputs = 0 V
2
IPDN
Current consumption in power-down
VCC < UVLOTH,
inputs = 0 V
1
UVLOTH
Undervoltage threshold
(VCC decreasing)
UVLOHYST
Undervoltage threshold hysteresis
POR
Power-on reset threshold
2.5
(VCC decreasing)
2.6
2.7
µA
V
100
mV
2.0
V
Current sensing
Vin_gg
Input voltage range
-40
IIN
Input current for CG pin
ADC_res
AD converter granularity
ADC_offset
AD converter offset
ADC_time
AD conversion time
ADC_acc
AD converter gain accuracy at full
scale (using external sense resistor)
FOSC
Internal time base frequency
Osc_acc
Internal time base accuracy
Cur_res
Current register LSB value
+40
mV
500
nA
5.88
CG = 0 V
-3
µV
3
500
25 °C
ms
0.5
Over temperature range
1
32768
25 °C, VCC = 3.6 V
%
Hz
2
Over temperature and
voltage ranges
2.5
5.88
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LSB
%
µV
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Electrical characteristics
STC3115
Table 4. Electrical characteristics (2.7 V < VCC < 4.5 V, -20 ° C to 70 ° C) (continued)
Symbol
Parameter
Conditions
Min
Typ
Max
Units
4.5
V
Battery voltage and temperature measurement
Vin_adc
Input voltage range
VCC = 4.5 V
LSB
LSB value
ADC_time
AD conversion time
Volt_acc
2.7 V < Vin < 4.5 V,
Battery voltage measurement accuracy VCC = Vin 25 °C
Voltage measurement
Temperature measurement
Over temperature range
Temp_acc
0
Internal temperature sensor accuracy
2.20
mV
1
°C
250
ms
-0.25
+0.25
-0.5
+0.5
-3
3
°C
0.35
V
%
Digital I/O pins (SCL, SDA, ALM, RSTIO)
Vih
Input logic high
1.2
Vil
Input logic low
Vol
Output logic low (SDA, ALM, RSTIO)
Iol = 4 mA
0.4
BATD/CD pin
Vith
Input threshold voltage
Vihyst
Input voltage hysteresis
Voh
Output logic high
(charge inhibit mode enable)
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1.46
1.61
1.76
0.1
Ioh = 3 mA
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V
Vbat0.4
STC3115
Electrical characteristics
Table 5. I2C timing - VIO= 2.8 V, Tamb = -20 °C to 70 ° C (unless otherwise specified)
Symbol
Parameter
Min
Typ
Max
Unit
400
kHz
Fscl
SCL clock frequency
thd,sta
Hold time (repeated) START condition
0.6
tlow
LOW period of the SCL clock
1.3
thigh
HIGH period of the SCL clock
0.6
tsu,dat
Setup time for repeated START condition
0.6
thd,dat
Data hold time
0
tsu,dat
Data setup time
100
tr
Rise time of both SDA and SCL signals
20+
0.1Cb
tf
Fall time of both SDA and SCL signals
20+
0.1Cb
tsu,sto
Setup time for STOP condition
0.6
µs
tbuf
Bus free time between a STOP and
START condition
1.3
µs
Cb
Capacitive load for each bus line
0
µs
0.9
ns
300
ns
300
ns
400
pF
Figure 3. I2C timing diagram
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Application information
5
STC3115
Application information
Figure 4. Example of an application schematic using the STC3115 in mixed mode
Optional filter
IO voltage
VCC
SCL
SDA
STC3115
C1
VIN
C2
BATD/CD
ALM
R1
Other
detection
circuit
R2
Rid
RSTIO
GND
Battery pack
CG
Rcg
Table 6. External component list
Name
Value
Tolerance
Comments
Rcg
5 to 50 mΩ
1% to 5%
C1
1 µF
C2
220 nF
Battery voltage input filter (optional)
R1
1 kΩ
Battery voltage input filter (optional)
R2
1 kΩ
Battery detection function
Current sense resistor (2% or better recommended)
Supply decoupling capacitor
Figure 5. Example of an application schematic using the STC3115 without current
sensing
Optional filter
IO voltage
VCC
SCL
SDA
STC3115
VIN
BATD/CD
ALM
RSTIO
GND
10/34
R1
C1
CG
DocID023755 Rev 7
C2
R2
Other
detection
circuit
Rid
Battery pack
STC3115
Application information
Table 7. External component list
Name
Value
C1
1 µF
C2
220 nF
R1
1 kΩ
R2
1 kΩ
Comments
Supply decoupling capacitor
Battery voltage input filter (optional)
Battery detection function
Figure 6. Example of an application layout using the STC3115 with current sensing (top view)
1. This track is a dedicated power supply track for the STC3115 system which, for voltage measurement
accuracy, is isolated from the application Vbat plane.
2. The STC3115 GND pin should be connected to the RCG only and for current measurement accuracy, it
should be isolated from the ground plane.
3. The STC3115 CG pin should be connected to the RCG first and for current measurement accuracy, it
should be isolated from the battery minus power path.
Note:
For a detailed explanation of the RCG layout, please refer to the AN4324 (Place and route
guidelines).
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Functional description
STC3115
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 STC3115 can operate in two different modes with different power consumption (see
Table 8. Mode selection is made by the VMODE bit in register 0 (refer to Table 13 for
register 0 definition).
Table 8. STC3115 operating modes
VMODE
Description
0
Mixed mode, Coulomb counter is active, voltage gas gauge runs in parallel
1
Voltage gas gauge with power saving
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.
The conversion cycle takes 213 = 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 12).
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STC3115
6.1.3
Functional description
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.
The conversion cycle takes 213 = 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 12).
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 12).
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Functional description
STC3115
6.2
STC3115 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 7. Coulomb counter block diagram
16-bit counter
REG_COUNTER
register
REG_CURRENT
register
EOC
CG
GND
CC SOC
calculator
AD converter
CC SOC
register (internal)
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 mA.h battery capacity).
The Coulomb counter is inactive if the VMODE bit is set, this is the default state at poweron-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 mA.h
Example: Rsense =10 mΩ, Cnom = 1650 mA.h, REG_CC_CNF = 333
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STC3115
6.2.2
Functional description
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 STC3115.
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 8. Voltage gas gauge block diagram
Voltage register
VM configuration
VIN
AD
converter
OCV value
Voltage mode
(VM)
algorithm
Reference
OCV
curve
To SOC
management
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 mA.h
Example: Ri = 190 mΩ, Cnom =1650 mA.h, REG_VM_CNF = 321
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Functional description
6.2.3
STC3115
Mixed mode gas gauge system
The STC3115 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 STC3115 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 STC3115 automatically uses the best method in any given application condition.
However, when the application enters standby mode, the STC3115 can be put in powersaving mode: only the voltage-mode gas gauge stays active, the Coulomb counter is
stopped and power consumption is reduced.
Figure 9. Mixed mode gas gauge block diagram
Voltage mode
gas gauge
(VM)
SOC
management
Coulomb
counter
(CC)
REG_SOC
register
Alarm
management
Parameter
tracking
REG_VM_ADJ
register
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:
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•
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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STC3115
6.3
Functional description
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 STC3115 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 STC3115 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
6.4
STC3115
Power-up and battery swap detection
When the STC3115 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 10. 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 STC3115 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 11. 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
STC3115 restarts
Example: When BATD/CD is high (voltage above the 1.61 V threshold) for more than 1 s, a
battery swap is detected. The STC3115 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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STC3115
6.5
Functional description
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 VCC voltage which inhibits the charge function
(assuming that the BATD/CD signal is connected to disable input of the charger circuit).
•
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 12 describes the BATD/CD and RSTIO operation at power-up. Please refer to the
block diagram of Figure 13 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 12. BATD and RSTIO timing diagram at power-up
delay
SOC
OCV
calc.
meas.
Application can start,
charge is enabled
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 STC3115 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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34
Functional description
STC3115
Figure 13. BATD and RSTIO
VCC
BATD_drive_high
BATD/CD
+
-
1.61 V
RSTIO
BATD_comp_out
RSTI
RSTO
STC3115
The BATD/CD pin used as a battery detector is an analog I/O.The input detection threshold
is typically 1.61V.
BATD/CD is also an output connected to VCC level when active. Otherwise, it is high
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 STC3115 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 14. BATD/CD pin connection when used as battery detector
STC3115
STC3115
Ru
Other biasing
and/or detection
circuit
(>1 M)
Battery
pack
Battery pack
BATD/CD
BATD/CD
1K
Rid
BATD resistor biasing
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DocID023755 Rev 7
1K
Rid
BATD biasing by external circuitry
I2C interface
STC3115
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. The default device address value is 1110 000. The STC3115 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 9. Device address format
bit7
bit6
bit5
bit4
bit3
bit2
bit1
bit0
1
1
1
0
0
0
0
R/W
Table 10. Register address format
bit7
bit6
bit5
bit4
bit3
bit2
bit1
bit0
RegADDR7
RegADDR6
RegADDR5
RegADDR4
RegADDR3
RegADDR2
RegADDR1
RegADDR0
Table 11. Register data format
bit7
bit6
bit5
bit4
bit3
bit2
bit1
bit0
DATA7
DATA6
DATA5
DATA4
DATA3
DATA2
DATA1
DATA0
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34
I2C interface
STC3115
Figure 15. Read operation
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22/34
DocID023755 Rev 7
I2C interface
STC3115
7.2
Register map
7.2.1
Register map
The register space provides 30 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 12. Detailed descriptions of
registers 0 (REG_MODE) and 1 (REG_CTRL) are shown in Table 13 and Table 14. 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 12. Register map
Name
Control registers
Address
(decimal)
Type
POR
Soft
POR
Description
LSB
0 to 23
REG_MODE
0
R/W
Mode register
REG_CTRL
1
R/W
Control and status register
REG_SOC (L-H)
2-3
R/W
Gas gauge relative SOC
1/512%
REG_COUNTER (L-H)
4-5
R
0x00
0x00
Number of conversions
(2 bytes)
500 ms
REG_CURRENT (L-H)
6-7
R
0x00
0x00
Battery current value
(2 bytes)
5.88 µV
REG_VOLTAGE (L-H)
8-9
R
0x00
0x00
Battery voltage value
(2 bytes)
2.2 mV
REG_TEMPERATURE
10
R
0x00
0x00
Temperature data
REG_CC_ADJ_HIGH
11
R
0x00
0x00
Coulomb counter adjustment
factor
REG_VM_ADJ_HIGH
12
R
0x00
0x00
Voltage mode adjustment
factor
REG_OCV (L-H)
13-14
R/W
0x00
0x00
OCV register (2 bytes)
REG_CC_CNF (L-H)
15-16
R/W
395
395
Coulomb counter gas gauge
configuration
REG_VM_CNF (L-H)
17-18
R/W
321
321
Voltage gas gauge algorithm
parameter
REG_ALARM_SOC
19
R/W
0x02
0x02
SOC alarm level
(default = 1%)
REG_ALARM_VOLTAGE
20
R/W
0xAA
0xAA
Battery low voltage alarm
level (default is 3 V)
17.6 mV
REG_CURRENT_THRES
21
R/W
0x0A
0x0A
Current threshold for the
relaxation counter
47.04 µV
REG_RELAX_COUNT
22
R
0x78
0x78
Relaxation counter
REG_RELAX_MAX
23
R/W
0x78
0x78
Relaxation counter max
value
REG_ID
24
R
0x14
0x14
Part type ID = 14h
DocID023755 Rev 7
1 °C
1/2%
0.55 mV
1/2%
23/34
34
I2C interface
STC3115
Table 12. Register map (continued)
Address
(decimal)
Type
POR
Soft
POR
Description
REG_CC_ADJ_LOW
25
R
0x00
0x00
Coulomb counter adjustment
factor
REG_VM_ADJ_LOW
26
R
0x00
0x00
Voltage mode adjustment
factor
ACC_CC_ADJ (L-H)
27-28
R
0x00
0x00
Coulomb Counter correction
accumulator
ACC_VM_ADJ (L-H)
29-30
R
0x00
0x00
Voltage mode correction
accumulator
Name
RAM registers
LSB
1/512%
32 to 47
REG_RAM0
32
R/W
...
...
REG_RAM15
47
R/W
48 to 63
R/W
Random Unchanged
Working register 0 for gas
gauge
...
Random Unchanged
Working register 15 for gas
gauge
OCV adjustment
registers
REG_OCVTAB
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0x00
0x00
DocID023755 Rev 7
OCV adjustment table
(16 registers)
0.55 mV
I2C interface
STC3115
7.2.2
Register description
Values held in consecutive registers (such as the charge value in the REG_SOC register
pair) are stored with low bits in the first register and high 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 13. REG_MODE - address 0
Name
Position
Type
Def.
VMODE
0
R/W
1
0: Mixed mode (Coulomb counter active)
1: Power saving voltage mode
CLR_VM_ADJ
1
R/W
0
Write 1 to clear ACC_VM_ADJ and
REG_VM_ADJ.
Auto clear bit if GG_RUN = 1
CLR_CC_ADJ
2
R/W
0
Write 1 to clear ACC_CC_ADJ and REG_CC_ADJ
Auto clear bit if GG_RUN = 1
ALM_ENA
3
R/W
1
Alarm function
0: Disabled
1: Enabled
0
0: Standby mode. Accumulator and counter
registers are frozen, gas gauge and battery
monitor functions are in standby.
1: Operating mode.
0
Forces the mixed mode relaxation timer to switch
to the Coulomb counter mode.
Write 1, self clear to 0
Relaxation counter = 0
0
Forces the mixed mode relaxation timer to switch
to voltage gas gauge mode.
Write 1, self clear to 0
Relaxation counter = Relax_max
GG_RUN
FORCE_CC
FORCE_VM
4
5
6
7
R/W
R/W
R/W
Description
Unused
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34
I2C interface
STC3115
Table 14. REG_CTRL - address 1
Name
IO0DATA
Position
Def.
R
X
ALM pin status
0 = ALM input is low
1 = ALM input is high
W
1
ALM pin output drive
0 = ALM is forced low
1 = ALM is driven by the alarm conditions
0
Description
GG_RST
1
W
0
0: no effect
1: resets the conversion counter
GG_RST is a self-clearing bit.
GG_VM
2
R
0
Voltage mode active
0 = REG_SOC from Coulomb counter mode
1 = REG_SOC from Voltage mode
BATFAIL
3
R/W
0
Battery removal or UVLO detection bit.
Write 0 to clear
(Write 1 is ignored)
R
1
Power on reset (POR) detection bit
0 = no POR event occurred
1 = POR event occurred
W
0
Soft reset
0 = release the soft-reset and clear the POR
detection bit,
1 = assert the soft-reset and set the POR detection
bit.
This bit is self clearing.
PORDET
4
ALM_SOC
5
R/W
0
Set with a low-SOC condition.
Cleared by writing 0.
ALM_VOLT
6
R/W
0
Set with a low-voltage condition.
Cleared by writing 0.
7
26/34
Type
Unused
DocID023755 Rev 7
STC3115
8
Package information
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.
DocID023755 Rev 7
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34
Package information
8.1
STC3115
Flip Chip CSP 1.40 x 2.04 mm package information
Figure 17. 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
area” typically 0.2 mm in diameter depending on the die size.
28/34
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STC3115
Package information
Table 15. Flip Chip CSP 1.4 x 2.04 mm package mechanical data
Dimensions
Ref.
Millimeters
Inches
Min.
Typ.
Max.
Min.
Typ.
Max.
A
0.545
0.600
0.655
0.021
0.024
0.026
A1
0.165
0.200
0.235
0.006
0.008
0.009
A2
0.330
0.350
0.370
0.013
0.014
0.015
b
0.220
0.260
0.300
0.009
0.010
0.012
D
1.98
2.01
2.04
0.078
0.079
0.080
D1
E
1.20
1.34
E1
1.37
0.047
1.40
0.053
0.800
0.054
0.055
0.031
e
0.360
0.400
0.440
0.014
0.016
0.017
fD
0.395
0.405
0.415
0.016
0.016
0.016
fE
0.275
0.285
0.295
0.011
0.011
0.012
G
ccc
0.050
0.002
0.050
0.002
Figure 18. Flip Chip CSP 1.4 x 2.04 mm footprint recommendation
DocID023755 Rev 7
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34
Package information
8.2
STC3115
DFN10 2.0 x 3.0 mm package information
Figure 19. DFN10 2.0 x 3.0 mm package mechanical drawing
30/34
DocID023755 Rev 7
STC3115
Package information
Table 16. DFN10 2.0 x 3.0 mm package mechanical data
Dimensions
Ref.
Millimeters
Inches
Min.
Typ.
Max.
Min.
Typ.
Max.
A
0.5
0.55
0.60
0.020
0.022
0.024
A1
0.00
0.05
0.000
b
0.15
0.23
0.30
0.006
0.009
0.012
D
2.90
3.00
3.10
0.114
0.118
0.122
E
1.90
2.00
2.10
0.075
0.079
0.083
e
0.50
0.002
0.020
L
0.45
0.505
0.65
0.018
0.020
0.026
L1
0.60
0.70
0.80
0.024
0.028
0.031
ddd
0.080
0.003
Figure 20. DFN10 2.0 x 3.0 mm footprint recommendation
DocID023755 Rev 7
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34
Ordering information
9
STC3115
Ordering information
Table 17. Order code
Order code
Temperature range
STC3115IJT(1)
STC3115AIJT(2)
STC3115IQT
(1)
Package
-40 °C to +85 °C
Tape and reel
DFN10 2x3
1. 4.35 V max battery option (3.8 V typ)
2. 4.20 V max battery option (3.7 V typ)
DocID023755 Rev 7
Marking
O22
CSP-10
STC3115AIQT(2)
32/34
Packing
O23
O204
O205
STC3115
10
Revision history
Revision history
Table 18. Document revision history
Date
Revision
22-Nov-2012
1
Initial release
2
Table 4: added “BATD” and “CD”
Section 6.4: removed option “RSTIO/BATD”
Section 6.5: added “BATD” and “CD”
Section 6.5.1: removed option 2 (BATD/CD is disabled) and 3 (BATD
and RSTIO); removed Figure: BATD and RSTIO - option 2, Figure:
BATD and RSTIO - option 3, and Figure: RSTIO/BATD pin
connection when used as battery detector - option 1 and 2; updated
text with respect to BATD/CD.
Removed Section: Register map (Device 0x13) - engineering
samples.
Updated Table 12
Removed Table: REG_MODE - address 0 (Device 0x13)
Removed Table: Internal default OCV table and OCV offset registers.
Removed Equation 3.
Replaced Figure 17: Flip Chip CSP 1.40 x 2.04 mm package
mechanical drawing.
Updated Table 15: Flip Chip CSP 1.4 x 2.04 mm package
mechanical data.
Updated Table 17: Order code
30-Oct-2013
3
Replaced silhouette
Updated Features
Updated Equation 1
Updated example of Equation 2
Updated disclaimer
28-Jan-2014
4
Corrected typographical error in document title.
08-Aug-2014
5
Added DFN10 2.0 mm x 3.0 mm package
6
Section 5: Application information: added Figure 6 and note relating
to AN4324.
Updated Section 7.1: Read and write operations
Updated Table 12: Register map
7
Removed the BATD option when it occurred with RSTIO
Figure 13: BATD and RSTIO: added STC3115
Updated text and Table 9: Device address format of Section 7.1:
Read and write operations.
Updated text and Table 12: Register map of Section 7.2.1: Register
map.
Updated text of Section 7.2.2: Register description
Updated Table 17: Order code
07-Feb-2013
06-Oct-2014
17-Dec-2014
Changes
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STC3115
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