Battery monitor IC with Coulomb counter/gas gauge
Features
■ Battery voltage monitoring
■ Internal temperature sensor
■ Coulomb counter with 12/14-bit AD converter,
+/- 80 mV input voltage range
■ Internal or external 32768 Hz time base
■ I2C interface for gas gauge monitoring and
device control
■ 32-RAM bytes
■ 8-byte unique device ID
■ One general-purpose I/O
Applications
STC3100
MiniSO-8
(Plastic micropackage)
DFN8 3x3
(Plastic micropackage)
■ Cellular phones, PDA, MP3 players, cordless
phones
■ Digital cameras, USB appliances, Bluetooth
devices
Description
The STC3100 monitors the critical parameters of
a single-cell Li-Ion battery (voltage, temperature
and current) and includes hardware functions to
implement a gas gauge for battery charge
monitoring, based on a programmable 12- to
14-bit A/D converter. With a typical 30 milliOhms
external sense resistor, the battery current can be
up to 2.5 A and the accumulator system provides
a capacity up to +/-7000 mAh with a resolution of
0.2 mAh.
The device is programmable through the I2C
interface.
IO0
ROSC
SDA
SCL
Pin connections
(top view)
1
2
3
4
8
7
6
5
VIN
VCC
CG
GND
January 2009 Rev 1 1/21
www.st.com
21
Block diagram STC3100
1 Block diagram
Figure 1. STC3100 internal block diagram
VCC
SCL
SDA
Accumulators and
control registers
I2C interface
1.2 V
reference
AD converter
11 bits (unsigned)
AD converter
12 / 14 bits (signed)
General-purpose I/O line
RAM & ID registers
32 kHz
time base
GND
MUX
Oscillator ROSC
Temp sensor
VIN
CG+
CG-
CG
IO0
AM00830
2/21
STC3100 Pin assignment
2 Pin assignment
Table 1. STC3100 pin description
Pin # Pin name Type Function
1 IO0 I/OD General-purpose I/O
2ROSC I_AD
3 SDA I/OD I2C serial data
4 SCL I_D I2C serial clock
5 GND Ground Analog and digital ground
6 CG I_A Gas gauge current sense input
7 VCC Supply Power supply
8 VIN I_A Battery voltage sense input
Note: I: input
O: output
OD: open drain
A: analog
D: digital
Oscillator bias resistor or external 32 kHz clock for gas
gauge
3/21
Absolute maximum ratings and operating conditions STC3100
3 Absolute maximum ratings and operating conditions
Table 2. Absolute maximum ratings
Symbol Parameter Value Unit
Vmax Maximum voltage on any pin 7 V
Vio Voltage on I/O pins -0.3 to 7 V
Tstg Storage temperature -55 to 150
Tj Maximum junction temperature 150
ESD Electrostatic discharge (HBM human body model) 2 kV
Table 3. Operating conditions
Symbol Parameter Value Unit
° C
° C
Vcc Operating supply voltage on V
CC
2.7 to 5.5 V
Vin Input voltage on Vin 0 to Vcc V
Vmin Minimum voltage on VCC for RAM content retention 2.0 V
Toper Operating free air temperature range -40 to 85
° C
4/21
STC3100 Electrical characteristics
4 Electrical characteristics
Table 4. Electrical characteristics (2.7 V < VCC < 4.5 V, -20° C to 70° C)
Symbol Parameter Conditions Min Typ Max Units
Supply
I
CC
Operating current consumption Average value over 4s 100 uA
Istby Current consumption in standby standby mode, inputs=0V 2 uA
Ipdn Current consumption in power down V
UVLOth Undervoltage threshold (V
< UVLOth, inputs=0V 1 uA
CC
decreasing) 2.5 2.6 2.7 V
CC
UVLOhyst Undervoltage threshold hysteresis 100 mV
POR Power-on reset threshold (V
decreasing) 2.0 V
CC
Gas gauge A/D converter
Vin_gg Input voltage range -80 +80 mV
Iin Input current for CG pin 500 nA
ADC_res AD converter granularity
12 bits
13 bits
14 bits
47.08
23.54
11.77
CG = 0V
ADC_offset AD converter offset
ADC_time AD conversion time (32768Hz clock)
ADC_acc AD converter gain accuracy at full scale
12 bits
13 bits
14 bits
12 bits
13 bits
14 bits
25° C
over temperature range
-2
-2
-3
125
250
500
2
LSB
2
LSB
3
LSB
0.51%
Fosc Internal time base frequency Rosc = 200 kΩ, 0.1% 32768 Hz
Osc_acc Internal time base accuracy
25° C, V
CC
=3.6V
over temperature and
voltage ranges
2
2.5%%
Fosc_ext External time base frequency range 30 70 kHz
uV
uV
uV
ms
ms
ms
%
Cur_res Current register LSB value 11.77 uV
Chg_res
Global_
CG_acc
Charge register LSB value
(32,768 Hz clock)
Gas gauge accuracy (not including the
external sense resistor tolerance)
=Cur_res*2^12*0.5/3600
Using internal time base
Using external time base
6.70 uV.h
3.51%
%
5/21
Electrical characteristics STC3100
Table 4. Electrical characteristics (2.7 V < VCC < 4.5 V, -20° C to 70° C) (continued)
Symbol Parameter Conditions Min Typ Max Units
Battery voltage and temperature a/d converter
Vin_adc Input voltage range Vcc = 5 V 0 5 V
LSB LSB value
ADC_time AD conversion time (32,768 Hz clock) 250 ms
Volt_acc Battery voltage measurement accuracy 2.7 V<Vin<4.5 V, VCC=Vin -0.5 +0.5 %
Temp_acc Internal temperature sensor accuracy -3 +3 °C
Digital I/O pins (SCL, SDA, IO0)
Vih Input logic high 1.2 V
Vil Input logic low 0.35 V
Vol Output logic low (SDA, IO0) Iol = 4 mA 0.4 V
Voltage measurement
Temperature measurement
2.44
0.125
mV
°C
6/21
STC3100 Typical performance curves
5 Typical performance curves
Figure 2. Standby current vs. temperature Figure 3. Current measurement accuracy vs.
temperature
1.6
1.4
1.2
1.0
0.8
Istby (uA)
0.6
0.4
0.2
0.0
Vcc=4.5V
-50-250 255075100125
Temp (°C)
Figure 4. Oscillator frequency accuracy vs.
temperature
2.0
1.5
1.0
0.5
0.0
-0.5
Osc_acc (% )
-1.0
-1.5
-2.0
-50 -25 0 25 50 75 100 125
Temp (°C)
0.6
Vgg=80mV
0.4
0.2
0.0
ADC_acc (%)
-0.2
-0.4
-0.6
-50 -25 0 25 50 75 100 125
Temp (°C)
Figure 5. Voltage measurement accuracy vs.
temperature
0.6
Vin= 3.5V
0.4
0.2
0.0
Volt_acc ( %)
-0.2
-0.4
-0.6
-50-25 0 25 50 75100125
Temp (°C)
7/21
Application information STC3100
6 Application information
Figure 6. Example of an application schematic using the STC3100
Rosc
ROSC
IO voltage
VCC
VIN
C1
STC3100
SCL
SDA
Table 5. External components list
GND
CG
IO0
Name Value Tolerance Comments
Rcg 10 to 50 mΩ 1% Gas gauge sense resistor
Rosc 200 kΩ 0.1% Internal oscillator bias resistor
C1 1 µF Supply decoupling capacitor
C2 220 nF Battery voltage input filter (optional)
R1 1 kΩ Battery voltage input filter (optional)
Optional filter
R1
C2
Rcg
AM00831
8/21
STC3100 Functional description
7 Functional description
7.1 Gas gauge
The gas gauge is used to monitor the available battery capacity. The voltage drop across the
external sense resistor is integrated during a conversion period and input to a 12- to 14-bit
AD converter. The output conversion is accumulated into a 28-bit accumulator. The system
controller can control the gas gauge and read the data (upper 16 bits of the accumulator)
through the I2C control registers.
The AD converter output is in two’s complement format. When a conversion cycle is
completed, the result is added to the charge accumulator and the number of conversions is
incremented in a 16-bit counter.
Figure 7. Gas gauge block diagram
CG
GND
12/14-bit
AD converter
EOC
2
cg_res
cg_clock
cg_enable
cg_calibration
Control
registers
16
16
16
rd_req
Counter
register
Current
register
Charge
register
AM00832
16-bit counter
28
28-bit
accumulator
16
32768 Hz
3
28
cg_rst
Control logic
The controller can read the value of the most recent conversion in two’s complement format
by reading the REG_CURRENT registers. These registers are updated at the end of each
conversion.
The differential inputs are scaled to the full range of the AD converter, introducing a small
offset error. A high value written to the CG_CAL bit of the control register connects the
inputs of the AD converter together, allowing the controller to measure the digital offset
error. Using this measurement, one can calibrate the gas gauge and reduce errors due to
the internal offset error.
9/21
Functional description STC3100
The conversion cycle for n bit resolution is 2n clock cycles. Using the 32,768 Hz internal
clock, the conversion cycle time is 125 to 500 ms for a 12- to 14-bit resolution. The LSB
value is set by the internal gain and internal reference and is 11.77 uV at maximum
resolutions. When using an external 30 milliOhms sense resistor, the 28-bit accumulator
results in a capacity of approximately +/- 7300 mA.h. The upper 16 bits of the accumulator
can be read from the I2C interface, giving a resolution of 0.2 mA.h.
When the battery voltage falls below the under voltage lockout threshold at 2.7 V, the gas
gauge system is stopped and the STC3100 stays in standby mode with minimum quiescent
current. All registers are maintained down to 2.0 V. Below 2.0 V, the registers are reset to
their default power-on value.
The gas gauge system needs an accurate 32,768 Hz timebase to compute the level of
charge flowing from/to the battery. The STC3100 can operate from an internal oscillator, or
use an external RTC signal for highest accuracy.
7.2 Battery voltage and temperature monitoring
The battery voltage and chip temperature (close to the battery temperature) are measured
by means of an A/D converter and a multiplexer. This function takes place concurrently to
the gas gauge function with a dedicated A/D converter, which means that it does not affect
the performance of the gas gauge. To reduce the power consumption, a conversion takes
place only every two seconds, alternatively for battery voltage and temperature (so each
value is refreshed every four seconds).
The conversion cycle takes 2
conversion cycle time is 250 ms. The resolution is 2.44 mV for the battery voltage and
0.125° C for the temperature.
13
= 8192 clock cycles. Using the 32,768 Hz internal clock, the
7.3 General-purpose input/output
A general-purpose I/O line is available. The output is an open drain, and an external pull-up
resistor may be needed in the application. Writing the IO0DATA bit to 0 forces the IO0 output
low; writing the IO0DATA bit to 1 leaves the IO0 output in a high impedance state. Reading
the IO0DATA bit gives the state of the IO0 pin.
In standby (CG_RUN=0), reset (PORDET set to 1) and power-down (Vcc<UVLOth) states,
the IO0 output is open and the input is read as zero whatever is the actual state of the IO0
pin.
7.4 RAM registers
The STC3100 provides 32 RAM registers to store any information regarding battery status,
charge cycles, battery aging, proprietary informations, etc...
The register content is maintained during standby and low voltage states, down to the
power-on reset level of approximately 2.0 V. Below this level, the content is not preserved.
This usually means that the Li-Ion cell was very deeply discharged and has been damaged.
10/21
STC3100 Functional description
7.5 Unique device ID
The STC3100 provides a means to identify the battery pack or the subsystem. Each device
has its own unique 8-byte ID made of an 8-bit part ID (value = 10h for the STC3100), a
48-bit random unique ID and an 8-bit CRC.
The CRC-8 is calculated according to bytes REG_ID0 to REG_ID6 using the "x8 + x2 + x +
1" polynomial with a zero initial value.
Since the device ID is downloaded from the ROM at power-up and is subsequently kept in
read-only RAM locations together with the general-purpose RAM registers, the device ID
can also be used as an indicator of the RAM integrity.
11/21
I2C interface STC3100
8 I2C interface
8.1 Read and write operations
The interface is used to control and read the current accumulator and registers. It is
compatible with the Philips I2C registered trademark (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 is shifted
to and from the chip on the SDA line, MSB first.
The first bit must be high (START) followed by the device address and read/write bit control.
Bits DevADDR0 to DevADDR2 are factory-programmable, the default device address value
being 70h (AddrID0 = AddrID1 = AddrID2 = 0). The STC3100 then sends an acknowledge
at the end of an 8-bit long sequence. The next 8 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 6. Device address format
b7 b6 b5 b4 b3 b2 b1 b0
1110DevADDR2 DevADDR1 DevADDR0 R/W
Table 7. Register address format
b7 b6 b5 b4 b3 b2 b1 b0
RegADDR7 RegADDR6 RegADDR5 RegADDR4 RegADDR3 RegADDR2 RegADDR1 RegADDR0
Table 8. Register data format
b7 b6 b5 b4 b3 b2 b1 b0
DATA7 DATA6 DATA5 DATA4 DATA3 DATA2 DATA1 DATA0
12/21
STC3100 I2C interface
Figure 8. Read operation
Master
Start Device addr Reg address
Start bit = SDA falling when SCL = 1
Stop bit = SDA rising when SCL = 1
Restart bit = start a
Acknowledge = SDA forced low during a SCL clock
7 bits 7 bits
Slave
W
fter a start
A
8 bits
Figure 9. Write operation
Start Device addr Reg address
Start bit = SDA falling when SCL = 1
Stop bit = SDA rising when SCL = 1
Restart bit = start after a start
7 bits8 bits
A
Restart Device addr
W
A
8 bits
A
Reg data
Reg data
A
R
8 bits
Reg data
A
8 bits
Address
n+1
A
A
Reg data
8 bits
Address
n+1
Reg data
8 bits
Address
n+2
A
A
Reg data
8 bits
Address
n+2
Stop
AM00834
A
Stop
AM00833
13/21
I2C interface STC3100
8.2 Register map
The register space provides 12 control registers, 8 read-only (factory OTP) registers for
unique device ID and 32 read/write general-purpose RAM registers. Mapping of all registers
is shown in Ta bl e 9 . Detailed descriptions of registers 0 (REG_MODE) and 1 (REG_CTRL)
are shown in Ta bl e 10 and Ta bl e 1 1 . 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 9. Register map
Name
Control registers 0 to 23
REG_MODE 0 R/W Mode register
REG_CTRL 1 R/W Control and status register
REG_CHARGE_LOW 2 R Gas gauge charge data, bits 0-7
REG_CHARGE_HIGH 3 R Gas gauge charge data, bits 8-15
REG_COUNTER_LOW 4 R Number of conversions, bits 0-7
REG_COUNTER_HIGH 5 R Number of conversions, bits 8-15
REG_CURRENT_LOW 6 R Battery current value, bits 0-7
REG_CURRENT_HIGH 7 R Battery current value, bits 8-15
REG_VOLTAGE_LOW 8 R Battery voltage value, bits 0-7
REG_VOLTAGE_HIGH 9 R Battery voltage value, bits 8-15
REG_TEMPERATURE_LOW 10 R Temperature value, bits 0-7
REG_TEMPERATURE_HIGH 11 R Temperature value, bits 8-15
Device ID registers 24 to 31
REG_ID0 24 R Part type ID = 10h
REG_ID1 25 R Unique part ID, bits 0-7
Address
(decimal)
Type Description
REG_ID2 26 R Unique part ID, bits 8-15
REG_ID3 27 R Unique part ID, bits 16-23
REG_ID4 28 R Unique part ID, bits 24-31
REG_ID5 29 R Unique part ID, bits 32-39
REG_ID6 30 R Unique part ID, bits 40-47
REG_ID7 31 R Device ID CRC
RAM registers 32 to 63
REG_RAM0 32 R/W General-purpose RAM register 0
... ... ...
REG_RAM31 63 R/W General-purpose RAM register 31
14/21
STC3100 I2C interface
Values held in consecutive registers (such as the charge value in the REG_CHARGE_LOW
and REG_CHARGE_HIGH 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 will be consistent.
The charge data is coded in 2’s complement format, and the LSB value is 6.70 uV.h.
The battery current is coded in 2’s complement format, and the LSB value is 11.77 uV. In
13-bit resolution mode, the 0 bit is always set to zero. In 12-bit resolution, bits 0 and 1 are
always set to zero.
The battery voltage is coded in binary format, and the LSB value is 2.44 mV.
The temperature value is coded in 2’s complement format, and the LSB value is 0.125° C.
The temperature of 0° C corresponds to code 0.
Table 10. REG_MODE - address 0
Name Pos. Type Def. Description
SEL_EXT_CLK 0 R/W 0
GG_RES [2,1] R/W 00
GG_CAL 3 R/W 0
32,768 Hz clock source:
0: auto-detect, 1: external clock
Gas gauge ADC resolution:
00:14 bits, 01:13 bits, 10:12 bits
0: no effect
1: used to calibrate the AD converters
0: standby mode. Accumulator and counter
GG_RUN 4 R/W 0
registers are frozen, gas gauge and battery
monitor functions are in standby.
1: operating mode.
[7..5] Unused
Table 11. REG_CTRL - address 1
Name Pos. Type Def. Description
RX
Port IO0 data status:
0 = IO0 input is low, 1 = IO0 input is high
IO0DATA 0
W1
Port IO0 data output drive:
0 = IO0 output is driven low,1 = IO0 output is open
0: no effect
GG_RST 1 W 0
1: resets the charge accumulator and conversion
counter. GG_RST is a self-clearing bit.
GG_EOC 2 R 1
VTM_EOC 3 R 1
Set at the end of a battery current conversion
cycle. Clears upon reading.
Set at the end of a battery voltage or temperature
conversion cycle. Clears upon reading.
Power on reset (POR) detection bit:
R1
0 = no POR event occurred,
1 = POR event occurred
PORDET 4
W0
Soft reset:
0 = release the soft-reset and clear the POR
detection bit, 1 = assert the soft-reset and set the
POR detection bit.
[7..5] Unused
15/21
Package information STC3100
9 Package information
In order to meet environmental requirements, ST offers these devices in different grades of
ECOPACK
specifications, grade definitions and product status are available at: www.st.com.
ECOPACK
®
packages, depending on their level of environmental compliance. ECOPACK®
®
is an ST trademark.
16/21
STC3100 Package information
9.1 MiniSO-8 package information
Figure 10. MiniSO-8 package mechanical drawing
Table 12. Miniso-8 package mechanical data
Dimensions
Ref.
Min. Typ. Max. Min. Typ. Max.
A1.100.043
A1 0.15 0.006
A2 0.75 0.85 0.95 0.030 0.033 0.037
b 0.22 0.40 0.009 0.016
c 0.08 0.23 0.003 0.009
D 2.80 3.00 3.20 0.110 0.118 0.126
E 4.65 4.90 5.15 0.183 0.193 0.203
E1 2.80 3.00 3.10 0.110 0.118 0.122
e 0.65 0.026
L 0.40 0.60 0.80 0.016 0.024 0.031
L1 0.95 0.037
L2 0.25 0.010
k0 8
ccc 0.10 0.004
Millimeters Inches
17/21
Package information STC3100
9.2 DFN8 package information
Figure 11. DFN8 3x3x1.0 mm package mechanical drawing (pitch 0.5 mm)
Table 13. DFN8 3x3x1.0 mm package mechanical data (pitch 0.5 mm)
Dimensions
Ref.
Min. Typ. Max. Min. Typ. Max.
A 0.80 0.90 1.00 0.031 0.035 0.039
A1 0.02 0.05 0.0008 0.0019
A2 0.55 0.65 0.80 0.021 0.025 0.031
A3 0.20 0.008
b 0.18 0.25 0.30 0.007 0.010 0.012
D 2.85 3.00 3.15 0.112 0.118 0.124
D2 2.20 2.70 0.087 0.106
E 2.85 3.00 3.15 0.112 0.118 0.124
E2 1.40 1.75 0.055 0.069
e 0.50 0.020
L 0.30 0.40 0.50 0.012 0.016 0.020
ddd 0.08 0.003
Millimeters Inches
18/21
STC3100 Ordering information
10 Ordering information
Table 14. Order codes
Part number
STC3100IST
STC3100IQT DFN8 3 x 3
Temperature
range
-40°C, +85°C
Package Packing Marking
MiniSO-8
Tape & reel O201
19/21
Revision history STC3100
11 Revision history
Table 15. Document revision history
Date Revision Changes
27-Jan-2009 1 Initial release.
20/21
STC3100
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