Battery Fuel Gauge Evaluation Kit
Demonstrates the capabilities of the DS2751
Multichemistry Battery Fuel Gauge,
- Temperature Measurement
- Voltage Measurement
- Current Measurement
- Current Accumulation
- Information Storage
- Identification
Interfaces to the Serial Port of a PC Running
Windows® 95 or Newer
Evaluation Kit Contents
Equipment Needed
Setup and Installation
Board Connections
Software Installation
Selecting the COM Port
Program Menus
Register Windows
Program Tabs
Real Time Meters
Data Logging
User Memory
Pack Information
Fuel Gauging
1 pc. TSSOP Evaluation Board
1 pc. DS9123 Serial Port Adapter
1 pc. RJ-11 Phone Cable
1 pc. DS2751K CD Containing:
DS2751K Evaluation Software
DS2751 Related Data Sheets
1. A PC Running Windows 95 or Newer with a
CD-ROM Drive and an Available Serial Port.
2. Cables with Mini-Grabber Style Clips or the
Ability to Solder Directly to Connection Pads.
3. A Battery and a Power Supply and/or Load
The DS2751K evaluation kit makes performance evaluation, software development, and prototyping with
the DS2751 multichemistry battery fuel gauge easy. The evaluation board interfaces to PC through a
DS9123 serial port adapter and RJ-11 cable connection. The provided CD-ROM contains all related data
sheets along with the evaluation software, which can be run under Windows 95, Windows 98, or
Windows NT.
*Kit demonstration boards will vary as they are improved upon over time. For information on the
demonstration board circuits refer to the documentation directory on the DS2751K CD-ROM.
Windows is a registered trademark of Microsoft Corp.
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The DS2751K evaluation software gives the user complete control of all functions of the DS2751.
Separate control tabs allow the user access to all EEPROM and RAM memory locations, all control
registers, and real-time updates of all monitored parameters. The software also incorporates a data
logging feature to monitor a cell over time and fuel-gauging algorithms to improve remaining capacity
calculations based on specific cell characteristics.
The evaluation board circuit is designed to provide the DS2751 with accurate parameter measurements
and protect the DS2751 from ESD damage. Kit demonstration boards will vary as they are improved
upon over time. For information on the demonstration board circuits refer to the documentation directory
on the DS2751K CD-ROM.
Connections to the demonstration board are best made either by soldering directly to the pads or by using
cables with mini-grabber clips. Communication to the board can be accomplished by connecting the RJ11 jack to the DS9123 serial port adapter with the provided 2 conductor cable. Then the DQ and PACterminals on the RJ-11 jack can be wired directly to the DQ and PAC- pads on the demonstration board.
Figure 1 shows the recommended circuit for the DS2751K demonstration board. The Li+ cell or NiMH
cell stack is connected between the BAT+ and BAT- pads. If a Li+ cell is used a protection circuit must
be included between the battery and the demo board. The user system load circuit/charger is connected
from BAT+ to PAC-. The evaluation software can be run with or without a load or charger as long as a
cell is connected between the BAT+ and BAT- terminals providing a minimum of 2.7V to power the
Figure 1. PD010203 Cell, Load, and Charger Connections
RJ-11 Jack
To install the DS2751K software, exit all programs currently running and insert the DS2751K software
CD into your computer’s CD-ROM. The user can run SETUP.EXE from the setup directory and the
installation process begins. Follow the prompts to complete the installation. The DS2751K software can
be uninstalled in the Add/Remove Programs tool in the Control Panel. After the installation is complete,
open the DS2751K folder and run DS2751K.EXE or select DS2751K from the program menu. A splash
screen containing information about the evaluation kit appears as the program is being loaded.
The documentation directory also located on the CD contains all relevant data sheets and application
notes on the DS2751 and DS2751K. They are stored in Adobe Acrobat format for easy viewing.
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The first time the software runs, the Serial Port Settings window appears. In this window, select the COM
port to which the DS9123 is attached and the desired communication rate; then hit OK. The DS2751K
software saves this COM port selection and automatically uses the selection each time the program starts.
To change the COM port later, click the Preferences option on the menu bar, select Serial Port Settings,
and then select the appropriate port. To attempt to automatically locate the DS9123, click the Poll Serial
Ports button. Warning—automatically polling for the DS9123 can disrupt other devices connected to
your computer’s COM ports.
Several pulldown menu options have been provided to simplify use of the DS2751K software for the
user. Their functions are individually detailed below.
The File menu allows the user to store information from a file directly into the Device Setup, Battery
Data, and Fuel-Gauging Data sections under the Pack Info tab or take the same pack information and
store to a file. These functions do not directly write or read the DS2751. It is still necessary for the user to
store or recall this information to or from the device by issuing a WRITE or READ command under the
Pack Info tab.
The Registers menu gives immediate access to all three status and function registers of the DS2751.
Selecting any of the registers will open an individual control window giving the user a description of each
register bit and the ability to read or write it. See the status register window example.
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The present state of all register bits are displayed immediately upon opening the register window. R/W
locations contain a selection field to allow the user to determine their state. Pressing either the Apply or
OK button in the EEPROM Register or Special Feature Register windows will automatically update and
read the corresponding register inside the DS2751. The Status Register has default values stored in user
EEPROM addresses 0x31h. Their windows contain extra options to write or read these locations
independently of their registers.
The Preferences menu allows the user to change COM port settings at any time. Edit Preferences opens
the Select Preferences window. See Selecting the COM Port above.
Selecting the About topic from the Help menu will open a window containing information about this
program and Dallas Semiconductor.
All functions of the program are divided under five tabs in the main program window. Left click on the
appropriate tab to move to the desired function page. Located under the Meters tab is all information on
real-time updates measured by the DS2751: voltage, current, accumulated charge, temperature, and the
status of the PIO and POR bits of the Special Feature Register. The Data Log tab allows the user to store
all real time information to a file. The Memory tab displays the contents of every register and memory
location inside the DS2751 and allows the user to alter the data. The Pack Information tab gives the user
the ability to assign a default device configuration and store that information to the DS2751 and/or a file.
The Fuel Gauging tab uses the cell characterization information stored under Pack Info to maintain a high
accuracy remaining capacity indicator.
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The Meters screen displays the latest real-time measurements of cell voltage, temperature, current and
accumulated charge with both analog meter readouts and digital values. The sense resistor value used to
calculate the current reading is shown in the current section. Left click on it or go to the sense resistor
sub-tab under Pack Info to change this value. The Calibrate Offset button in the current section allows the
user to zero the current measurements under the conditions of their circuit. Left clicking this button will
begin the automatic calibration procedure. Calibration should be performed while the pack is
disconnected and there is no current flow. The next 32 readings will be averaged and the offset eliminated
by adjusting the Current Offset Register (location 0x33h) automatically. The process takes approximately
20 seconds.
The user can bring up the Update Current Accumulator window by left clicking the Set ACR button. This
window allows the user to enter values for the Current Accumulator Register and Rated Battery Capacity
in mAH. Rated Battery Capacity is used to determine full scale range on the Accumulated Charge Meter.
This value is stored in software only. Changing this value from the Update Current Accumulator window
will adjust the Charge Remaining.
The present states of the PIO bit and the POR bit of the Special Feature Register are shown at the bottom
of the window. The user can toggle the value of the bits by left clicking on the associated button.
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The Datalog tab allows the user to see the DS2751’s parameter measurements graphed over time. There
are separate sub-tabs for voltage, current, temperature, and accumulated charge. Each graph displays the
last 500 data points collected by the DS2751K software. The sampling interval can be adjusted from 1
second to 15 minutes and can be adjusted from the Sampling Interval menu at the bottom of the window.
The Clear Graphs button will clear all data from all four graphs, but does not reset the log to file
The Log to File sub-tab contains control information for storing all log data to an ASCII file. The default
filename is c:\DS2751K_datalog.txt, but can be modified in the filename text field. The Log Data button
toggles data logging off and on. Data will be stored at the same interval selected for updating the graphs
in the tab delimited format of
for easy import into a spreadsheet. The most recent 50 samples are displayed in the window for
observation. Warning—the Log Data function overwrites previous file information. Data previously
stored in the file will be lost.
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The Memory tab gives the user access to all 11 register, 32 EEPROM, and 16 SRAM bytes inside the
DS2751. They are separated into four sub-tabs for convenience. Any value can be modified by clicking in
that address’ text box and typing a new value in hexadecimal format. The Write button will copy the
entire block of data to the corresponding location inside the DS2751 (scratchpad RAM on the EEPROM
blocks). The Read button will update the entire block’s text boxes with data from the DS2751 (scratchpad
RAM on the EEPROM blocks). Sub-tabs displaying any EEPROM data will also have Copy and Recall
buttons to allow the user to transfer the data between scratchpad and EEPROM memory internal to the
DS2751. The Permanently Lock Block 0/1 buttons will permanently store the data currently located in
that block’s EEPROM if the LOCK bit in the EEPROM register is set. Otherwise this button will do
nothing. Warning—this data can never be changed once locked. Verify your data first by issuing a Recall
and a Read.
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The Pack Information tab gives the pack manufacturer the ability to assign default register settings,
device and sense resistor selection, and recommended manufacturer data and fuel gauging information.
The Device Select sub-tab allows the user to choose which device on the 1-Wire bus to communicate
with. Clicking on the Find DS2751 Net Addresses button will begin a SEARCH NET ADDRESS
operation on the 1-Wire bus. All DS2751s found on the bus will be listed in the Net Addresses field. To
communicate to any device on the bus, click on its address inside the Net Addresses field to select it. The
program will now use this device for all operations until a different DS2751 is chosen.
The Device Setup sub-tab shows the current state of all major features of the DS2751. All status
indicators shown here directly mirror their corresponding bits in the Status and Special Feature registers.
Clicking on any of the status indicators will open the corresponding register window to allow editing. See
Registers menu above. The selection fields on the right hand side of the sub-tab set how the EEPROM
backup bits (locations 0x31h) will be programmed when the DS2751 is programmed with the pack
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The Sense Resistor Select sub-tab allows the user to correct the current measurements if a different value
of sense resistor is used. All DS2751s with an integrated sense resistor use 25mWs. If the sense resistor is
located externally, the user should select the external resistor radio button on this tab, then enter the value
of the resistor in mWs in the Sense Resistor Value field and then click the Write Sense Resistor button.
The Find Sense Resistor button opens the Find Sense Resistor window. The user can then determine the
resistance by forcing a known current and measuring the voltage drop with the DS2751. The resistance
value is stored with ¼ mW resolution into the user EEPROM of the device. The program uses this value
to convert the voltage difference from the VSENS+ and VSENS- pins into milliamps. If this value does
not match the value of the external resistor, current measurements will be inaccurate.
The Battery Data and Fuel Gauging Data sub-tabs demonstrate how the pack manufacturer can use the
DS2751s EEPROM fields to store relevant pack information such as manufacturer, chemistry, etc. The
fuel gauging characterization data is used by the fuel gauging algorithms in the software. See the Fuel
Gauging tab description below. Clicking on the Load Default Pack Info button will enter example data
into the information fields of the Device Setup, Battery Data, and Fuel Gauging Data sub-tabs. To
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change any of this information, simply click on the desired text field and enter the new value. Once all
data is in the desired format, click on the Write DS2751 button to copy it to the EEPROM of the DS2751.
This information can also be stored to a file and recalled later using the Load/Save Pack Info buttons.
Fuel Gauging – Full Point at 0°C
Fuel Gauging – Full Point difference from 10°C to 0°C
Fuel Gauging – Full Point difference from 20°C to 10°C
Fuel Gauging – Full Point difference from 30°C to 20°C
Fuel Gauging – Full Point difference from 40°C to 30°C
Total Accumulated Discharge – Divided by 20 to store in 2 bytes
Scalar – Stored in 2 bytes with 100% equal to 1000h
Fuel Gauging – Time from Break Point to Full at 0°C
Fuel Gauging – Time from Break Point to Full at 20°C
Fuel Gauging – Time from Break Point to Full at 40°C
Fuel Gauging – Time from Empty to Full at 0°C
Fuel Gauging – Time from Empty to Full at 20°C
Fuel Gauging – Time from Empty to Full at 40°C
Fuel Gauging – Charge Time Estimation Break Point
Current Offset – Do not overwrite
Sense Resistor (1/4mW resolution)
Date Code – 2 bytes
Fuel Gauging – Standby Empty Point difference from 0°C to 10°C
Fuel Gauging – Standby Empty Point difference from 10°C to 20°C
Fuel Gauging – Standby Empty Point difference from 20°C to 30°C
Fuel Gauging – Standby Empty Point difference from 30°C to 40°C
Fuel Gauging – Active Empty Point difference from 0°C to 10°C
Fuel Gauging – Active Empty Point difference from 10°C to 20°C
Fuel Gauging – Active Empty Point difference from 20°C to 30°C
Fuel Gauging – Active Empty Point difference from 30°C to 40°C
Fuel Gauging – Active Empty Point at 40°C
The memory map above shows the format in which the data is stored within the device. All static data is
stored in Block 1 while data which might need to be updated is in Block 0. The pack manufacturer can
now permanently lock Block 1 to maintain data integrity while leaving Block 0 open for access by the
host processor.
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The final program tab performs a high accuracy calculation of remaining cell capacity using Dallas
Semiconductor’s fuel gauging algorithms. For this feature to function properly, cell characterization data
must be stored in the DS2751’s user EEPROM. See the Pack Information section above. If
characterization data cannot be found, the fuel gauge will not start and an error message will be
displayed. The Relative Capacity number represents what percentage of cell capacity is remaining based
on present algorithm inputs such as temperature, discharge rate, etc. This value is also reflected in the
analog meter. The remaining cell capacity is also displayed in terms of milliamp-hours and Joules under
Absolute Capacity and Remaining Energy respectively.
The remaining run time is calculated using the Run Time Power Reference input from the user.
Instantaneous current measurements in the user’s application can vary greatly. By using a reference scalar
instead of actual current and voltage measurements, the program produces a stable estimation of
remaining run time. The user should enter the largest expected power draw from the device into the Run
Time Power Reference field for the most accurate estimation.
If this example were part of a fully integrated fuel gauging system, the algorithms would need to be
updated by the host each time the cell was fully charged or discharged in order to maintain long term
accuracy. To simulate this, the user should click the Empty or Full buttons each time the monitored pack
is completely charged or discharged. The Empty button will reset the Current Accumulator to the
expected empty point based on present conditions. The Full button will set the Current Accumulator the
expected full point based on present conditions. The Learn button will reset the expected full point to the
present Current Accumulator value and update the fuel gauging information in the DS2751’s user
EEPROM. In doing this, the algorithms “learn” from previous results and are more accurate in the future.
This tab gives an example only of fuel gauging. For more information on the process of high-accuracy
fuel gauging consult Dallas Semiconductor’s fuel gauging application notes.
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This datasheet has been download from:
Datasheets for electronics components.