DS2764K Maxim Integrated, DS2764K Datasheet - Page 12

• Manufacturer Part Number: DS2764K
• Description: Power Management IC Development Tools
• Manufacturer: Maxim Integrated
• Series: DS2764r

DS2764EVKIT+
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 DS2764’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 DS2764’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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