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DS2751E-DS2751E/T&R
Multichemistry Fuel Garge
FEATURES ��Available in Two Configurations
- Internal 25m� Sense Resistor - External User-Selectable Sense Resistor
��Current Measurement 12-Bit Bidirectional Measurement Internal Sense Resistor Configuration: 0.625mA LSB and ±1.9A Dynamic Range External Sense Resistor Configuration:
15.625�V LSB and ±64mV Dynamic
Range
��Current Accumulation - Internal Sense Resistor: 0.25mAhr LSB External Sense Resistor: 6.25�Vhr LSB
��Voltage Measurement with 4.88mV
Resolution
��Temperature Measurement Using Integrated
Sensor with 0.125�C Resolution
��32 Bytes of Lockable EEPROM
��16 Bytes of General-Purpose SRAM
��Dallas 1-Wire® Interface with Unique 64-Bit Device Address
��Supports 1-Cell Li+/Polymer or 3-Cell Ni
Battery Packs
��3mm Dimension of 8-Pin TSSOP Package
Allows Mounting on Side of Thin Li+ and Li+/Polymer Cells (Lead Free available)
��Low Power Consumption:
- Active Current: 60�A (typ), 90�A (max)
- Sleep Current: 1�A (typ), 2�A (max)
PIN CONFIGURATION
PIN DESCRIPTION
DS2751
Multichemistry Battery
Fuel Gauge DS2751E
8-Pin TSSOP Package
(Lead Free Available)
VINDQ
SNS
IS2 PIO
VSS
VDDIS1
1-Wire is a registered trademark of Dallas Semiconductor.
DS2751
ORDERING INFORMATION Note 1: A “+” will be marked on the package near the Pin 1 indicator.
DESCRIPTION The DS2751 multichemistry battery fuel gauge is a data-acquisition and information-storage device
tailored for cost-sensitive and space-constrained 1-cell Li+/polymer or 3-cell Ni battery-pack
applications. The DS2751 provides the key hardware components required to accurately estimate remaining capacity by integrating low-power, precision measurements of temperature, voltage, current,
and current accumulation, as well as nonvolatile (NV) data storage, into the small footprint of a 3.0mm x
4.4mm 8-pin TSSOP package.
Through its 1-Wire interface, the DS2751 gives the host system read/write access to status and control registers, instrumentation registers, and general-purpose data storage. Each device has a unique factory-
programmed 64-bit net address that allows it to be individually addressed by the host system, supporting
multibattery operation.
The DS2751 performs temperature, voltage, and current measurement to a resolution sufficient to support process-monitoring applications such as battery charge control and remaining capacity estimation.
Temperature is measured using an on-chip sensor, eliminating the need for a separate thermistor.
Bidirectional current measurement and accumulation are accomplished using either an internal 25m�
sense resistor or an external device. The DS2751 also features a programmable I/O pin that allows the
host system to sense and control other electronics in the pack, including switches, vibration motors, speakers, and LEDs.
Three types of memory are provided on the DS2751 for battery information storage: EEPROM, lockable
EEPROM, and SRAM. EEPROM memory saves important battery data in true NV memory that is
unaffected by severe battery depletion, accidental shorts, or ESD events. Lockable EEPROM becomes ROM when locked to provide additional security for unchanging battery data. SRAM provides
inexpensive storage for temporary data.
DS2751
ABSOLUTE MAXIMUM RATINGS* Voltage on PIO Pin, Relative to VSS -0.3V to +12V
Voltage on All Other Pins, Relative to VSS -0.3V to +6V
Continuous Internal Sense Resistor Current �2.5A
Pulsed Internal Sense Resistor Current �50A for <100µs/s, <1000 Pulses Operating Temperature Range -40°C to +85°C
Storage Temperature Range -55°C to +125°C
Soldering Temperature See J-STD-020A Specification * This is a stress rating only and functional operation of the device at these or any other conditions above
those indicated in the operation sections of this specification is not implied. Exposure to absolute
maximum rating conditions for extended periods of time may affect reliability.
RECOMMENDED DC OPERATING CONDITIONS (TA = 2.5V � VDD � 5.5V, -20�C to +70�C.)
DC ELECTRICAL CHARACTERISTICS (TA = 2.5V � VDD � 5.5V, -20�C to +70�C.)
DS2751
ELECTRICAL CHARACTERISTICS: TEMPERATURE, VOLTAGE, CURRENT
(TA = 2.5V � VDD � 5.5V, -20�C to +70�C.)
ELECTRICAL CHARACTERISTICS—1-WIRE INTERFACE
(TA = 2.5V � VDD � 5.5V, -20�C to +70�C.)
DS2751
EEPROM RELIABILITY SPECIFICATION
(TA = 2.5V � VDD � 5.5V, -20�C to +70�C.)
Note 1: All voltages are referenced to VSS.
Note 2: Operating VIN > 4.5V relative to VSS, or VIN > VDD + 0.3V can induce errors in voltage,
temperature, or current measurements.
Note 3: Self heating due to output pin loading and sense resistor power dissipation can alter the
reading from ambient conditions.
Note 4: Although the Voltage Register is large enough to report values larger than 4.75V, the internal compensation for circuit variations can reduce the maximum reportable voltage to as low as
4.75V.
Note 5: Voltage offset measurement is with respect to 4.35V at +25°C.
Note 6: Internal current-sense resistor configuration.
Note 7: External current-sense resistor configuration.
Note 8: The Current Register supports measurement magnitudes up to 2.56A using the internal sense-
resistor option and 64mV with the external resistor option. Compensation of the internal
sense-resistor value for process and temperature variation may reduce the maximum
reportable magnitude to 1.9A.
Note 9: Current offset error null to ±1 LSb typically requires a one time 3.5s in-system calibration by user.
Note 10: Current gain-error specification applies to gain error in converting the voltage difference at
IS1 and IS2, and excludes any error remaining after the DS2751 compensates for the internal
sense-resistor’s temperature coefficient of 3700ppm/�C to an accuracy of �500ppm/�C. The
DS2751 does not compensate for external sense resistor characteristics, and any error terms arising from the use of an external sense resistor should be taken into account when
calculating total current measurement error.
Note 11: Typical value for tERR valid at 3.6V and +25�C.
Note 12: Four year data retention at +70�C.
DS2751
Figure 1. FUNCTIONAL DIAGRAM
CHIP GROUND
VIN
IS1
IS2
SNS
IS2IS1
VSS
PIO
DS2751
Figure 2. APPLICATION EXAMPLE
1) RSENS is present for external sense resistor configurations only.
2) RSENSINT is present for internal sense resistor configurations only.
POWER MODES
The DS2751 has two power modes: active and sleep. While in active mode, the DS2751 continuously measures current, voltage, and temperature to provide data to the host system to support current
accumulation. In sleep mode, the DS2751 ceases these activities. The DS2751 enters sleep mode when
PMOD = 1 and either of the following occur:
��the DQ line is low for longer than tSLEEP (2.2s) (pack disconnection).
��the UVEN bit in the Status Register is set to 1 and the voltage on VIN drops below undervoltage
threshold VUV for tUVD (cell depletion)
The DS2751 returns to active mode when the DQ line is pulled from a low-to-high state and the voltage
on VIN is above VUV. The factory default for the DS2751 is UVEN = PMOD = 0.
The DS2751 defaults to active mode when power is first applied.
PACK+
PACK-
DS2751
CURRENT MEASUREMENT
In the active mode of operation, the DS2751 continually measures the current flow into and out of the
battery by measuring the voltage drop across a current-sense resistor. The DS2751 is available in two
configurations: 1) internal 25m� current-sense resistor, and 2) external user-selectable sense resistor. In
either configuration, the DS2751 considers the voltage difference between pins IS1 and IS2 (VIS = VIS1 -VIS2) to be the filtered voltage drop across the sense resistor. A positive VIS value indicates current is
flowing into the battery (charging), while a negative VIS value indicates current is flowing out of the
battery (discharging).
VIS is measured with a signed resolution of 12 bits. The Current Register is updated in two’s-complement format every 88ms with an average of 128 measurements. Currents outside the range of the register are
reported at the limit of the range. The format of the Current Register is shown in Figure 3.
For the internal sense resistor configuration, the DS2751 maintains the Current Register in units of amps,
with a resolution of 0.625mA and full-scale range of no less than �1.9A (see Note 7 on IFS spec for more details). The DS2751 automatically compensates for internal sense-resistor process variations and
temperature effects when reporting current.
For the external sense resistor configuration, the DS2751 updates the measured VIS voltage to the Current
Register in units of volts, with a resolution of 15.625�V and a �64mV full-scale range.
Figure 3. CURRENT REGISTER FORMAT MSB—Address 0E LSB—Address 0F 2
MSb LSb MSb LSb
Units: 0.625mA for internal sense resistor
15.625�V for external sense resistor
CURRENT ACCUMULATOR The Current Accumulator facilitates remaining capacity estimation by tracking the net current flow into
and out of the battery. Current flow into the battery increments the Current Accumulator, while current
flow out of the battery decrements it. Data is maintained in the Current Accumulator in two’s-
complement format. The format of the Current Accumulator is shown in Figure 4. When the internal sense resistor is used, the DS2751 maintains the Current Accumulator in units of amp-
hours, with a resolution of 0.25mAhrs and a �8.2Ahrs full-scale range. When using an external sense
resistor, the DS2751 maintains the Current Accumulator in units of volt-hours, with a resolution of
6.25�Vhrs and a �205mVhrs full-scale range.
The Current Accumulator is a read/write register that can be altered by the host system as needed.
DS2751
Figure 4. CURRENT ACCUMULATOR FORMAT MSB—Address 10 LSB—Address 11 2
MSb LSb MSb LSb
Units: 0.25mAhrs for internal sense resistor
6.25�Vhrs for external sense resistor
CURRENT OFFSET COMPENSATION
Current measurement and the current accumulation are both internally compensated for offset on a
continual basis minimizing error resulting from variations in device temperature and voltage. Additionally, a constant bias can be utilized to alter any other sources of offset. This bias resides in
EEPROM address 33h in two’s-complement format and is subtracted from each current measurement.
The current offset bias is applied to both the internal and external sense resistor configurations. The
factory default for the current offset bias is a value of 0.
Figure 5. CURRENT OFFSET BIAS Address 33
MSb LSb
Units: 0.625mA for internal sense resistor
15.625�V for external sense resistor
VOLTAGE MEASUREMENT
The DS2751 continually measures the voltage between pins VIN and VSS over a 0 to 4.5V range. The Voltage Register is updated in two’s-complement format every 3.4ms with a resolution of 4.88mV.
Voltages above the maximum register value are reported as the maximum value. The Voltage Register
format is shown in Figure 6.
Figure 6. VOLTAGE REGISTER FORMAT MSB—Address 0C LSB—Address 0D 2
MSb LSb MSb LSb
Units: 4.88 mV
DS2751
TEMPERATURE MEASUREMENT
The DS2751 uses an integrated temperature sensor to continually measure battery temperature.
Temperature measurements are updated in the Temperature Register every 220ms in two’s-complement
format with a resolution of 0.125°C over a �127°C range. The Temperature Register format is shown in
Figure 7.
Figure 7. TEMPERATURE REGISTER FORMAT MSB—Address 18 LSB—Address 19 2
MSb LSb MSb LSb
Units: 0.125�C
PROGRAMMABLE I/O
To use the PIO pin as an output, write the desired output value to the PIO bit in the Special Feature Register. Writing a 0 to the PIO bit enables the PIO output driver, pulling the PIO pin to VSS. Writing a 1
to the PIO bit disables the output driver, allowing the PIO pin to be pulled high or used as an input. To
sense the value on the PIO pin, read the PIO bit. The DS2751 turns off the PIO output driver and sets the
PIO bit high when in sleep mode or when DQ is low for more than tSLEEP (2.2s), regardless of the state of
the PMOD bit.
MEMORY
The DS2751 has a 256-byte linear address space with registers for instrumentation, status, and control in the lower 32 bytes, with lockable EEPROM and SRAM memory occupying portions of the remaining
address space. All EEPROM and SRAM memory is general-purpose except addresses 31h and 33h,
which should be written with the default values for the Status Register and Current Offset Register,
respectively. When the MSB of any two-byte register is read, both the MSB and LSB are latched and held
for the duration of the Read Data command to prevent updates during the read and to ensure synchronization between the two register bytes. For consistent results, always read the MSB and the LSB
of a two-byte register during the same Read Data command sequence.
EEPROM memory is shadowed by RAM to eliminate programming delays between writes and to allow
the data to be verified by the host system before being copied to EEPROM. All reads and writes to/from
EEPROM memory actually access the shadow RAM. In unlocked EEPROM blocks, the Write Data command updates shadow RAM. In locked EEPROM blocks, the Write Data command is ignored. The
Copy Data command copies the contents of shadow RAM to EEPROM in an unlocked block of
EEPROM but has no effect on locked blocks. The Recall Data command copies the contents of a block of
EEPROM to shadow RAM regardless of whether the block is locked or not.
