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1 of 11 features ? demonstrates the capabilities of the ds2786 stand-alone ocv-based fuel gauge including: ? estimation of available capacity for li+ cells ? voltage measurement ? current measurement ? current accumulation ? temperature measurement ? information storage ? thermistor reading ? interfaces to the usb port of a pc running windows xp ? or older operating system evaluation kit contents 1 pc. evaluation board 1 pc. ds9123o usb port adapter 1 pc. rj-11 cable index evaluation kit contents equipment needed introduction setup and installation board connections software installation selecting the com port program menus menu windows status register current offset register program tabs real time tab memory tab parameters tab log data tab 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 li+ battery and a power supply and/or load circuit. ordering information part type DS2786EVKIT+ ev kit + denotes lead(pb)-free and rohs compliant. introduction the ds2786 evaluation kit (ev kit) makes performance eval uation, software development, and prototyping with the ds2786 stand-alone ocv-based fuel gauge easy. the evaluation board interfaces to a pc through a ds9123o usb adapter and rj-11 cable connection. separate control tabs allow the user acce ss to all memory locations, all contro l registers, and real-time updates of all monitored parameters. the software also incorporat es a data-logging feature to monitor a cell over time. the evaluation board circuit is designed to provide the ds 2786 with accurate parameter measurements as well. kit demonstration boards will vary as t hey are improved upon over time. for information on the demonstration board circuits, visit our website at www.maxim-ic.com. DS2786EVKIT stand-alone ocv-based fuel gauge evaluation kit 19-4856; rev 10/09 www.maxim-ic.com windows xp is a registered trademark of microsoft corp. downloaded from: http:///
DS2786EVKIT 2 of 11 setup and installation board connections connections to the tssop demonstration board are best made ei ther by soldering directly to the pads or by using cables with mini-grabber clips. communication to the tssop board can be accomplished either through the rj-11 jack by connecting the provided standard six conductor rj-11 cord. figures 1a and 1b show the recommended circuits to simula te charging and discharging. the li+ cell is connected between the b+ and b- pads. the battery charger/power supply or circuit load is connected between the b+ and p- pads. the evaluation software can be run in either configuration as long as a cell is connected between the b+ and b- terminals providing a minimum of 2.5v to power the ds2786. figure 1a: charging circuit fig 1b: discharging circuit software installation to install the ds2786 ev kit software, exit all progra ms currently running and download the latest ds2786 ev kit software from our website at www.ma xim-ic.com. unzip the compressed f ile and double click the setup.exe icon to being the installation process. follow the prompts to complete the installation. the ds2786 ev kit software can be uninstalled in the add/remove programs tool in the c ontrol panel. after the installation is complete, open the ds2786k folder and run ds278 6k.exe or select ds2786k fr om the program menu. a sp lash screen containing information about the evaluation kit appears as the program is being loaded. all relevant data sheets and application notes on the ds2786 and ds2786 ev kit can be found on our website at www.maxim-ic.com.. selecting the communication port the first time the software runs, the select preferences window may appear. in this window, select either serial port or usb communication and the port number; then hit ok. the ds2786 ev kit software saves this port selection and automatically uses the selection each time the program starts. to change the port later, click the preferences option on the menu bar, select port settings , and then select the appropriate port. to attempt to automatically locate the ds9123o, click the poll ports bu tton. warningautomatically polling for the ds9123o can disrupt other devices connected to your computers com ports. sgnd p + battery + - DS2786EVKIT evaluation board power supply / battery charger load p- sgnd p + battery + - DS2786EVKIT evaluation board p- downloaded from: http:///
DS2786EVKIT 3 of 11 program menus several pull down menu options have been provided to si mplify use of the ds2786 ev kit software for the user. their functions are individually detailed below. registers menu the registers menu gives immediate acce ss to the status register and the curr ent offset bias register of the ds2786. selecting either of the regist ers will open an individual control win dow giving the user a description of each register bit and the ability to read or write it. status/configuration register the present state of all register bits are displayed immediately upon opening the register window. r/w locations contain a selection field or command button to allow the user to determine their state. pressing the write status button will write the new value to the register and read th e corresponding register inside the ds2786 to verify the correct value was written. note: this window does not copy these values to eeprom. to copy the desired values to eeprom, see the parameters section. downloaded from: http:///
DS2786EVKIT 4 of 11 current offset bias register the current offset bias can be entered into the text box and then written to the device by left-clicking on the write button. a message box will be displayed asking if new offs et should be copied to eeprom . if yes is clicked, a 15v programming voltage will need to be connected to the vprog pin, as described in the memory section below. the calibrate offset button allows the software to auto- detect the current offset based on the reading of the current register. the read current register button will display the real ti me current re ading from the current register. preferences menu the preferences menu allows the user to change com port se ttings at any time. edit preferences opens the select preferences window. see selecting the communication port above. help menu selecting the about topic from the he lp menu will open a window containing in formation about the current revision of this program and dallas semiconductor. program tabs all functions of the program are divided under four tabs in the main program window. left click on the appropriate tab to move to the desired function page. located on the meters tab is all of the information measured and calculated by the ds2786. the memory tab displays the co ntents of every register and memory location inside the ds2786 and allows the user to alter the data. the paramete rs tab gives the user access to the entire parameter eeprom memory block. the data log tab allows the user to store all real time informat ion to a file and view the data in a graphical form. downloaded from: http:///
DS2786EVKIT 5 of 11 real-time tab the meters tab displays the latest real-time measurements of cell voltage, auxiliary inputs, temperature, current and relative capacity with both analog meter readouts and digital values. the auxiliary inputs can be used to measure an identific ation resistor or a thermistor that should be connected between ain0 / ain1 and sgnd. additionally, the ds2786 can be configured to return the temperature in the place of auxiliary input 1 by setting the itemp bit on the status/configuration register. update sense resistor the sense resistor value used to calculate the current reading is shown in the current section. left-click on the update sense resistor button to open the find sense resistor window. the value of the sense resistor is not stored by the ds 2786, but this value is stored on the host computer to calculate the current flowing across the sense resistor. this value will be remembered each time the ds2786 ev kit downloaded from: http:///
DS2786EVKIT 6 of 11 is started. the user can manually ent er the sense resistor value at the top of the window, or can allow the software to calculate the value. to allow the ds2786 ev ki t to calculate the sense resistor, simply enter the value of the current that is flowing across th e sense resistor in the current forced text box in terms of mamps. then left- click the calculate resistor button and the software will determine the value of the sense resistor and put the new value in the sense resistor value text box at the top of the wi ndow. click ok to accept the new sense resistor value, or click cancel to ignore the changes that were made. update reference resistors a known 10k resistor is used to determine the resistance of the auxiliary inputs. if the va lues of the resistors are not exactly 10k, or if other values are desired for the kn own resistors, simply left-click on the update resistors button and the update referenc e resistors window w ill appear. simply enter the correct refere nce resistance and left-click update. once again, this is only a software value, so it is not stored on the device, but it will be recalled each time the program is started. commands the commands section provides access to the commands of the command register. left-click on the stored ocv button to force an ocv calculation based on the voltage st ored as the initial voltage. this will modify both the relative capacity register and the last ocv register. left-click on the present ocv button to force an ocv calc ulation based on the present state of the voltage register. this command will also modify the relative capacity and last ocv registers. this command should only be sent when there is an ocv condition on the cell. if current is flowing, a ocv calculation value will occur based on a loaded voltage, rather than an open-circuit voltage. this error will persist until an actual ocv condition is encountered and an ocv calculation can take place. this command is very useful when the ds2786 ev kit is powered by a power supply and the voltage is changed quickly and the user wants to monitor the relative capacity change with changes in voltage. a power-on reset (por) can be forced by left-clicking on the force por button. this will send the ds2786 through its power on sequence. downloaded from: http:///
DS2786EVKIT 7 of 11 memory tab the memory tab gives the user access to read the content s of all of the memory inside the ds2786. the memory is divided into 3 sub-tabs which allows the user to view the real-time registers as well as the values stored in eeprom. memory addresses 60h C 7fh are eeprom location s. left-clicking the write or read buttons will access the shadow ram. left-clicking on the copy or recall buttons will tr ansfer the data between the eeprom locations and the shadow ram. a 15v programming voltage is required to copy the shadow ram to eeprom. the software will prompt the user when the programming voltage should be connected to the ds2786 ev kit board to insure proper programming. some memory locations in the ds 2786 are read-only, so they will no t be altered by writing them. downloaded from: http:///
DS2786EVKIT 8 of 11 parameters tab the parameters tab gives the user access to t he entire parameter eeprom memory. the ds2786 comes preloaded with a best fit curve that wa s calculated based on characterization da ta taken from cells of various sizes and manufacturers. to change any of this information, simp ly click on the desired text field and enter the new value. clicking on the load default set up button will enter example data into the information fields of the parameters tab. once all data is in the desired format, click on t he write & copy button to copy it to the eeprom of the ds2786. a message box will be displayed prompting the user to connect a 15v programming voltage which will need to be connected to the vprog pin in order for the data to be copied to the eeprom of the device. any changes to the information can also be stored to a file and recalled later using the load/save set up buttons or the load/save parameters set up menu items. these fu nctions do not directly write or read the ds2786. it is still necessary for the user to store or recall this information to or from the device by issuing a write or read buttons. downloaded from: http:///
DS2786EVKIT 9 of 11 data log tab the log data tab allows the user to see the ds2786s real time measurements graphed over time. there are separate sub-tabs for voltage, current, capacity, and auxiliary inputs. each graph displays the last 500 data points collected by the ds2786 ev kit software. the sampling interv al can be adjusted from as fast as possible 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 func tion. when the fastest sampling interval is selected, the graphs will not be updated, only the data logging is enabled. the log to file sub tab contains control information for storing all data to an ascii file. the default filename is c:\ds2786k_datalog.txt, but can be modified in the filename te xt 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 voltage current capacity auxin0 auxin1 initial voltage last ocv learned charge factor for easy import into a spreadsheet. the most recent 50 samples are displayed in the window for observation. warninghe log data function overwrites previous file inform ation. data previously stor ed in the file will be lost. downloaded from: http:///
DS2786EVKIT 10 of 11 ds2740 ev kit schematic downloaded from: http:///
DS2786EVKIT 11 of 11 revision history revision date description pages changed 10/09 changed the part number from ds2786k to DS2786EVKIT. all downloaded from: http:///

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