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PDF DS2781 Data sheet ( Hoja de datos )
| Número de pieza | DS2781 | |
| Descripción | 1-Cell or 2-Cell Standalone Fuel Gauge IC | |
| Fabricantes | Maxim Integrated Products | |
| Logotipo |  |
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DS2781
1-Cell or 2-Cell
Standalone Fuel Gauge IC
GENERAL DESCRIPTION
The DS2781 measures voltage, temperature, and
current, and estimates available capacity for
rechargeable Lithium-Ion and Lithium-Ion Polymer
batteries. Cell stack characteristics and application
parameters used in the calculations are stored in on-
chip EEPROM. The available capacity registers
report a conservative estimate of the amount of
charge that can be removed given the current
temperature, discharge rate, stored charge and
application parameters. Capacity estimation is
reported in milliamp hours remaining and percentage
of full.
APPLICATIONS
Digital Video Cameras
Commercial Two-Way Radios
Industrial PDAs and Handheld PC Data Terminals
Portablewww.DataSheet4U.com GPS Navigation Systems
TYPICAL OPERATING CIRCUIT
P+
DS2781
DQ
DQ VDD
PIO VIN
OVD
VB
SNS
VSS
P-
Protection
Circuit
FEATURES
§ Precision Voltage, Temperature, and Current
Measurement System
§ Operates in One-Cell or Two--Cell Applications
§ Accurate, Temperature Stable Internal Time
Base
§ Absolute and Relative Capacity Estimated from
Coulomb Count, Discharge Rate, Temperature,
and Battery Cell Characteristics
§ Accurate Warning of Low Battery Conditions
§ Automatic Backup of Coulomb Count and Age
Estimation to Nonvolatile (NV) EEPROM
§ Gain and Tempco Calibration Allows the Use of
Low-Cost Sense Resistors
§ 24-Byte Battery/Application Parameter EEPROM
§ 16-Byte User EEPROM
§ Unique ID and Multidrop 1-WireÒ Interface
§ Tiny 8-Pin TSSOP Package Embeds Easily in
Battery Packs Using Thin Prismatic Cells
PIN CONFIGURATION
TOP VIEW
TSSOP-8
VB
VSS
VIN
VPLS
1
2
3
4
8 PIO
7 SNS
6 OVD
5 DQ
ORDERING INFORMATION
PART
MARKING
DS2781E+
DS2781E+T&R
2781
2781
PACKAGE
TSSOP
Tape-and-Reel
+ Denotes lead-free package.
1-Wire is a registered trademark of Dallas Semiconductor.
Note: Some revisions of this device may incorporate deviations from published specifications known as errata. Multiple revisions of any device
may be simultaneously available through various sales channels. For information about device errata, click here: www.maxim-ic.com/errata.
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REV: 010906
1 page  
Figure 1. Block Diagram
DS2781: Two-Cell Standalone Fuel Gauge IC
VPLS
V POR
PIO
DQ
OVD
Voltage
Regulator
EN
1-Wire
Interface
BIAS/VREF
Status
&
Control
EEPROM
SNS
Accumulated
Current
Current ADC
15 bit + sign
Timebase
Temp
&
Voltage
ADC
Rate,
Temperature
Compensation
VB
VIN
VSS
DETAILED DESCRIPTION
The DS2781 operates directly from 2.5V to 10V and supports single or dual cell Lithium-ion battery packs.
Nonvolatile storage is provided for cell compensation and application parameters. Host side development of fuel-
gauging algorithms is eliminated. On-chip algorithms and convenient status reporting of operating conditions
reduce the serial polling required of the host processor.
Additionally, 16 bytes of EEPROM memory are made available for the exclusive use of the host system and/or
pack manufacturer. The additional EEPROM memory can be used to facilitate battery lot and date tracking and
non-volatile storage of system or battery usage statistics.
A Dallas 1-Wire interface provides serial communication at the standard 16kbps or overdrive 140kbps speeds
allows access to data registers, control registers and user memory. A unique, factory programmed 64-bit
registration number (8-bit family code + 48-bit serial number + 8-bit CRC) assures that no two parts are alike and
enables absolute traceability. The Dallas 1-Wire interface on the DS2781 supports multidrop capability so that
multiple slave devices may be addressed with a single pin.
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5 Page 
DS2781: Two-Cell Standalone Fuel Gauge IC
ACCUMULATION BIAS
The Accumulation Bias register (AB) allows an arbitrary bias to be introduced into the current-accumulation
process. The AB can be used to account for currents that do not flow through the sense resistor, estimate currents
too small to measure, estimate battery self-discharge or correct for static offset of the individual DS2781 device.
The AB register allows a user programmed constant positive or negative polarity bias to be included in the current
accumulation process. The user-programmed two’s compliment value, with bit weighting the same as the current
register, is added to the ACR once per current conversion cycle. The AB value is loaded on power-up from
EEPROM memory. The format of the AB register is shown in Figure 10.
Figure 10. Accumulation Bias Register Formats
AB
S 26
MSb
“S”: sign bit
Address 61h
EE
25 24 23 22 21 20
Units:
LSb
1.5625mV/Rsns
CURRENT BLANKING
The Current Blanking feature modifies current measurement result prior to being accumulated in the ACR. Current
Blanking occurs conditionally when a current measurement (raw current + COB) falls in one of two defined ranges.
The first range prevents charge currents less than 100µV from being accumulated. The second range prevents
discharge currents less than 25µV in magnitude from being accumulated. Charge current blanking is always
performed, however, discharge current blanking must be enabled by setting the NBEN bit in the Control register.
See the register description for additional information.
CAPACITY ESTIMATION ALGORITHM
Remaining capacity estimation uses real-time measured values and stored parameters describing the cell stack
characteristics and application operating limits. The following diagram describes the algorithm inputs and outputs.
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| PDF Descargar | [ Datasheet DS2781.PDF ] | |
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