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FEATURES
Demonstrates the capabilities of the DS2756
High Accuracy Battery Fuel Gauge,
including:
Programmable Suspend Mode
Temperature measurement
Voltage measurement
Current measurement
Current and Voltage Snapshot Mode
Current accumulation
Temperature and Accumulated Current
Alarms
Information storage
Identification
Interfaces to the USB port of a PC running
Windows XP or older
INDEX
Evaluation Kit Contents
Equipment Needed
Introduction
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
EVALUATION KIT CONTENTS
1 pc. TSSOP Evaluation Board
1 pc. DS9123O USB Adapter
1 pc. RJ-11 Phone Cable
EQUIPMENT NEEDED
1. A PC running Windows XP or older operating
system and an available USB port.
2. Cables with mini-grabber style clips or the
ability to solder directly to connection pads.
3. A Lithium-Ion battery and a power supply
and/or load circuit.
INTRODUCTION
The DS2756 evaluation kit (EV kit) makes performance evaluation, software development, and
prototyping with the DS2756 High Accuracy Battery Fuel Gauge easy. The evaluation board interfaces to
a PC through a DS9123O USB Adapter and RJ-11 cable connection.
The DS2756 EV kit evaluation software gives the user complete control of all functions of the DS2756.
Separate control tabs allow the user access to all EEPROM and RAM memory locations, all control
DS2756EVKIT+
High Accuracy Battery Fuel Gauge With
Pro
g
rammable Sus
p
end Mode Evaluation Kit
19-4847; Rev 9/09
www.maxim-ic.com
Windows XP is a registered trademark of Microsoft Corp.
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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 DS2756 with accurate parameter measurements
and protect the DS2756 from ESD damage. Kit demonstration boards will vary as they are improved
upon over time. For information on the demonstration board circuits refer to our website at www.maxim-
ic.com.
SETUP AND INSTALLATION
BOARD CONNECTIONS
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 RJ-
11 Jack to the DS9123O USB Adapter with the provided 6 conductor cable. Then the DQ and PAC-
terminals 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 DS2756EVKIT+ demonstration board. The Lithium-Ion
cell or NiMH cell stack is connected between the BAT+ and BAT- pads. If a Lithium-Ion 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 2.7 volts to power the DS2756.
Figure 1: PD010203 Ce ll, Load , and Charger Connections
SOFTWARE INSTALLATION
To install the DS2756 EV kit software, exit all programs currently running and download the latest
version at www.maxim-ic.com. Unzip the compressed file and double click SETUP.EXE to begin the
installation process. Follow the prompts to complete the installation. The DS2756 EV kit software can be
uninstalled in the Add/Remove Programs tool in the Control Panel. After the installation is complete,
open the DS2756K folder and run DS2756K.EXE or select DS2756K from the program menu. A splash
screen containing information about the evaluation kit appears as the program is being loaded.
SELECTING THE COM PORT
The first time the software runs, the Select Preferences window appears. In this window, select either
serial port or USB communication and the port number; then hit OK. The DS2756 EV kit software saves
this port selection and automatically uses the selection each time the program starts. To change the port
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later, click the Preferences option on the menu bar, select Edit Preferences, and then select the appropriate
port. To attempt to automatically locate the DS9123O, click the Poll Serial Ports button. Warning -
automatically polling for the DS9123O can disrupt other devices connected to your computer’s COM
ports.
MENUS
Several pull down menu options have been provided to simplify use of the DS2756 EV kit software for
the user. Their functions are individually detailed below.
FILE MENU
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 DS2756. 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.
REGISTERS MENU
The Registers Menu gives immediate access to all three status and function registers of the DS2756.
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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STATUS REGISTER
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 the WRITE or
WRITE & COPY buttons will automatically update the corresponding register inside the DS2756. The
Status register has default values stored in user EEPROM location 0x31h. That window contains extra
options to write or read the EEPROM location independently of the register in address 0x01h.
1 WIRE SPEED MENU
The 1 Wire Speed Menu allows the user to select the appropriate 1 Wire timing. The speed the device
uses is determined by the state of the OVD bit in the Status Register.
PREFERENCES MENU
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.
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HELP MENU
Selecting the About topic from the Help Menu will open a window containing information about this
program and Dallas Semiconductor.
PROGRAM TABS
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 DS2756: 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 DS2756 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 DS2756 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.
METERS TAB
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.
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The user can use the Snapshot Mode of the DS2756 by left clicking on the TAKE SNAP SHOT button.
This will send the Sync Function Command to the device that will take a Snap Shot of the Voltage and
Current registers and hold those values. When the device is in Snapshot Mode, this button will then read
RESUME. Left clicking on the RESUME button will clear the SNAP bit in the Special Feature register
and allow the device to return to normal operation
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 PIO bit by left clicking on the associated button. If
the POR bit is set, the user can clear the bit by left clicking on the associated button. If the POR bit is
cleared, the button will not be visible.
SETTING SUSPEND THRESHOLDS
The Suspend Thresholds set the current level that the device uses to determine if it should enter and exit
Suspend Mode. Left clicking on the Set Suspend Limits button will open a new window to allow the
high and low Suspend limits to be entered in terms of mA. Left clicking on the Write button will write
the appropriate EEPROM locations.
SETTING INTERRUPT THRESHOLDS
The bottom right side of the Meters Tab shows the alarm settings. Left clicking on the SET button will
open a new window to allow the high and low Temperature and ACR Alarm limits to be entered in terms
of degree C or mAhrs. Left clicking on the OK button will write the appropriate SRAM locations.
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ENABLING INTERRUPTS
The DS2756 can be configured in the Status Register to provide an interrupt on PIO or DQ. The
Interrupts are enabled by setting the Interrupt Enable (IE) bit in the Special Feature Register. Once the
Interrupts are enabled, all 1 Wire activity must stop because a 1 Wire Reset will clear the IE bit. So when
the user left clicks the ENABLE INTERRUPTS button, the above message box will be displayed. As
long as that message box is displayed, no 1 Wire activity is generated by the DS2756. The user must
monitor the PIO or DQ pins externally to observe the interrupt when one of the alarm limits is crossed.
SETTING ACCUMULATION BIAS
The user can update the Accumulation Bias Register by left clicking on the SET ACC BIAS button on the
Meters Tab. That will open up the Set Accumulation Bias Register window. When the user left clicks
the WRITE button the value that is entered into the New Accumulation Bias Value text box will be
written to the Accumulation Bias Register (location 0x33h). This new value will be added to the current
register on each conversion cycle. Clicking the WRITE button will also update the Offset Blanking
Enable (OBEN) bit of the Status Register with the value of the associated checkbox.
The FIND ACC BIAS button allows the software to auto-detect the appropriate Accumulation Bias
Register value based on the Average Current Reading. The auto-detection should be performed while the
pack is disconnected and there is no current flow. The process takes approximately 10 seconds.
SETTING ACCUMULATED CURRENT REGISTER
The user can bring up the Set Accumulated Current Register window by left clicking the Set ACR button
of the Meters Tab. This window allows the user to enter values for the Accumulated Current Register and
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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 and does not affect the Fuel Gauging
data.
DATALOG TAB
The Data log tab allows the user to see the DS2756’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 DS2756 EV kit 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
function.
The Log to File sub-tab contains information for storing all log data to an ASCII file. The default
filename is c:\DS2756K_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
“Time<tab>Voltage<tab>Current<tab>Temperature<tab>ACR”
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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MEMORY TAB
The Memory Tab gives the user access to all 13 register, 96 EEPROM, and 32 SRAM bytes inside the
DS2756. They are separated into eight 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
16 bytes of data on the tab to the corresponding location inside the DS2756 (Scratchpad RAM on the
EEPROM blocks). The READ button will update the entire tab’s text boxes with data from the DS2756
(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 DS2756. Each EEPROM block on the DS2756 is 32 bytes, so that Block 0 is
from location 0x20 to 0x3F, Block 1 is from 0x40 to 0x5F and Block 2 is from 0x60 to 0x7F. The
PERMANENTLY LOCK EEPROM BLOCK 0/1/2 buttons will permanently store the data currently
located in that block’s 32 bytes of EEPROM. Verify your data first by issuing a Recall and a Read on
both tabs of the EEPROM block.
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PACK INFORMATION TAB
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 DS2756 Net Addresses button will begin a SEARCH NET ADDRESS
operation on the 1-wire bus. All DS2756s 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 DS2756 is chosen.
The Device Setup sub-tab shows the current state of all major features of the DS2756. 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 (location 0x31h) will be programmed when the DS2756 is programmed with the pack
information.
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SETTING SENSE RESISTOR VALUE
The Sense Resistor Select sub-tab allows the user to correct the current measurements if a different value
of sense resistor is used. All DS2756s with an integrated sense resistor use 20mΩs. 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 mΩs 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 DS2756.
The resistance value is stored with ¼ mΩ 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.
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MEMORY MAP
The Battery Data and Fuel Gauging Data sub-tabs demonstrate how the pack manufacturer can use the
DS2756s 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 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 DS2756 button to copy it to the EEPROM of the
DS2756. This information can also be stored to a file and recalled later using the LOAD/SAVE PACK
INFO buttons.
MEMORY MAP OF PACK INFORMATION DATA
0x20
0x21 Fuel Gauging – Full Point at 0C
0x22 Fuel Gauging – Full Point difference from 10C to 0C
0x23 Fuel Gauging – Full Point difference from 20C to 10C
0x24 Fuel Gauging – Full Point difference from 30C to 20C
0x25 Fuel Gauging – Full Point difference from 40C to 30C
0x26
0x27 Total Accumulated Discharge – Divided by 20 to store in 2 bytes
0x28
0x29 Fuel Gauging – Age Scalar
0x2A Fuel Gauging – Time from Break Point to Full at 40C
0x2B Fuel Gauging – Time from Break Point to Full at 20C
0x2C Fuel Gauging – Time from Break Point to Full at 0C
0x2D Fuel Gauging – Time from Empty to Full at 40C
0x2E Fuel Gauging – Time from Empty to Full at 20C
0x2F Fuel Gauging – Time from Empty to Full at 0C
0x30 Sense Resistor (1/4m resolution)*
0x31 PMOD RNAOP SWEN
0x32 Fuel Gauging – Charge Estimation Break Point in mAH
0x33 Current Offset – Do not overwrite
0x34 Discharge Suspend Threshold
0x35 Charge Suspend Threshold
0x36 Date Code
0x37 Fuel Gauging – Standby Empty Point difference from 0C to 10C
0x38 Fuel Gauging – Standby Empty Point difference from 10C to 20C
0x39 Fuel Gauging – Standby Empty Point difference from 20C to 30C
0x3A Fuel Gauging – Standby Empty Point difference from 30C to 40C
0x3B Fuel Gauging – Active Empty Point difference from 0C to 10C
0x3C Fuel Gauging – Active Empty Point difference from 10C to 20C
0x3D Fuel Gauging – Active Empty Point difference from 20C to 30C
0x3E Fuel Gauging – Active Empty Point difference from 30C to 40C
Addresses
0x3F Fuel Gauging – Active Empty Point at 40C
The memory map above shows the format in which the data is stored within the device.
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* The FuelPack algorithm expects the sense resistor value will be stored in address 0x34h of the
UserData.Memory array that is passed to the algorithm. However, in EEPROM, that location is defined
in the DS2756 to be the Discharge Suspend Threshold and the sense resistor is stored in EEPROM
Memory location 0x30h as shown in the Memory Map. In order for the FuelPack algorithm to correctly
calculate the remaining capacity, the user must copy the value of the sense resistor register (EEPROM
Memory Address 0x30h) into the UserData.Memory(0x34h) prior to passing the structure to the FuelPack
algorithm. The DS2756 EV kit software automatically performs this operation.
FUEL GAUGING TAB
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 DS2756’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
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pack is completely charged or discharged. The EMPTY button will reset the Accumulated Current
Register to the expected empty point based on present conditions. The FULL button will set the
Accumulated Current Register to the expected full point based on present conditions. The LEARN button
will reset the expected full point to the present Accumulated Current Register value and update the fuel
gauging information in the DS2756’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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REVISION HISTORY
REVISION
DATE DESCRIPTION PAGES
CHANGED
9/09 Changed the part number from DS2756K to DS2756EVKIT+. All
