DS2751K

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/g167 Demonstrates the capabilities of the DS2751 Multichemistry Battery Fuel Gauge, Including: - Temperature Measurement - Voltage Measurement - Current Measurement - Current Accumulation - Information Storage - Identification /g167 Interfaces to the Serial Port of a PC Running Windows ® 95 or Newer 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. DS9123 Serial Port Adapter 1 pc. RJ-11 Phone Cable 1 pc. DS2751K CD Containing: DS2751K Evaluation Software DS2751 Related Data Sheets EQUIPMENT NEEDED 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 Circuit. INTRODUCTION The DS2751K evaluation kit makes performance evaluation, software development, and prototyping with the DS2751 multichemistry battery fuel gauge easy. Th e 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. DS2751K Battery Fuel Gauge Evaluation Kit www.maxim-ic.com PD010203* DS2751K TSSOP Windows is a registered trademark of Microsoft Corp.

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 automati cally 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. MENUS Several pulldown menu opti ons have been provided to simplify use of the DS2751K 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 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. REGISTERS MENU The Registers menu gives immediate access to all three st atus 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.

The present state of all register bits are disp layed 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 regi ster inside the DS2751. The Status Register has default values stored in user EEPROM addresses 0x31h. Their windows contain extr a options to write or read these locations independently of their registers. 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. HELP MENU Selecting the About topic from the Help menu will open a window contai ning information about this program and Dallas Semiconductor. PROGRAM TABS All functions of the program are di vided 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, cu rrent, 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 a nd 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.

The Meters screen displays the latest real-time measurements of cell voltage, temperature, current and accumulated charge with both analog meter readouts a nd 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 conditi ons of their circuit. Left clicking this button will begin the automatic calibration procedure. Calib ration 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 Curr ent Accumulator Register and Rated Battery Capacity in mAH. Rated Battery Capacity is used to deter mine 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.

The Datalog tab allows the user to see the DS2751’s pa rameter measurements graphed over time. There are separate sub-tabs for voltage, current, temperatur e, 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 function. The Log to File sub-tab contains control information for storin g 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 interv al 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 re cent 50 samples are displayed in the window for observation. Warning—the Log Data function overwrites previous f ile information. Data previously stored in the file will be lost.

The Memory tab gives the user access to all 11 regist er, 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 locati on 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 onc e locked. Verify your data first by issuing a Recall and a Read.

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 whic h 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 a ll major features of the DS2751. All status indicators shown here directly mirro r their corresponding bits in the St atus 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 DS 2751 is programmed with the pack information.

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 25m/g87s. 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 m /g87s 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 measur ing the voltage drop with the DS2751. The resistance value is stored with ¼ m /g87 resolution into the user EEPROM of the device. The program uses this value to convert the voltage difference from the VSENS+ a nd 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 rele vant 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 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. MEMORY MAP OF PACK INFORMATION DATA 0x20 0x21 Fuel Gauging – Full Point at 0/g176C 0x22 Fuel Gauging – Full Point difference from 10/g176C to 0/g176C 0x23 Fuel Gauging – Full Point difference from 20/g176C to 10/g176C 0x24 Fuel Gauging – Full Point difference from 30/g176C to 20/g176C 0x25 Fuel Gauging – Full Point difference from 40/g176C to 30/g176C 0x26 0x27 Total Accumulated Discharge – Divided by 20 to store in 2 bytes 0x28 0x29 Scalar – Stored in 2 bytes with 100% equal to 1000h 0x2A Fuel Gauging – Time from Break Point to Full at 0/g176C 0x2B Fuel Gauging – Time from Break Point to Full at 20/g176C 0x2C Fuel Gauging – Time from Break Point to Full at 40/g176C 0x2D Fuel Gauging – Time from Empty to Full at 0/g176C 0x2E Fuel Gauging – Time from Empty to Full at 20/g176C 0x2F Fuel Gauging – Time from Empty to Full at 40/g176C 0x30 Reserved 0x31 PMOD RNAOP UVEN 0x32 Fuel Gauging – Charge Time Estimation Break Point 0x33 Current Offset – Do not overwrite 0x34 Sense Resistor (1/4m/g87 resolution) 0x35 0x36 Date Code – 2 bytes 0x37 Fuel Gauging – Standby Empty Point difference from 0/g176C to 10/g176C 0x38 Fuel Gauging – Standby Empty Point difference from 10/g176C to 20/g176C 0x39 Fuel Gauging – Standby Empty Point difference from 20/g176C to 30/g176C 0x3A Fuel Gauging – Standby Empty Point difference from 30/g176C to 40/g176C 0x3B Fuel Gauging – Active Empty Point difference from 0/g176C to 10/g176C 0x3C Fuel Gauging – Active Empty Point difference from 10/g176C to 20/g176C 0x3D Fuel Gauging – Active Empty Point difference from 20/g176C to 30/g176C 0x3E Fuel Gauging – Active Empty Point difference from 30/g176C to 40/g176C Addresses 0x3F Fuel Gauging – Active Empty Point at 40/g176C 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.

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 DS 2751’s user EEPROM. See the Pack Information section above. If characterization data cannot be found, the fuel ga uge 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, discha rge rate, etc. This value is also reflected in the analog meter. The remaining cell capacity is also displayed in terms of millia mp-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 charge d 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 th e 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.