BQ34Z100 Datasheet, PDF (29/50 Pages) Texas Instruments – Wide Range Fuel Gauge with Impedance Track™ Technology

bq34z100
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SLUSAU1 – MAY 2012
• Cell Charge Voltage Tx-Ty: Enter the desired cell charge voltage for each JEITA temperature range.
STEP 2: Review and modify the Data Flash Configuration Registers.
• LED_Comm Configuration: See Table 13 and Table 14 to aid in selection of an LED mode. Note that the pin
used for the optional Alert signal is dependent upon the LED mode selected.
• Alert Configuration: See Table 15 to aid in selection of which faults will trigger the Alert pin.
• Number of Series Cells
• Pack Configuration: Ensure that the VOLSEL bit is set for multi-cell applications and cleared for single-cell
applications.
STEP 3: Design and Configure the Voltage Divider.
If the battery contains more than one series cells, a voltage divider network will be required. Design the divider
network, based on the formula below. The voltage division required is from the highest expected battery voltage,
down to approximately 900 mV. For example, using a lower leg resistor of 16.5 KΩ where the highest expected
voltage is 32000 mV:
Rseries = 16.5 KΩ ( 32000 mV – 900 mV) / 900 mV = 570.2 KΩ
Based on price and availability, a 600 K resistor or pair of 300 K resistors could be used in the top leg along with
a 16.5-K resistor in the bottom leg.
Set the Voltage Divider in the Data Flash Calibration section of the Evaluation Software to 32000 mV.
Use the Evaluation Software to calibrate to the applied nominal voltage, e.g.: 24000 mV. After calibration, a
slightly different value will appear in the Voltage Divider parameter, which can be used as a default value for the
project.
STEP 4: Determine the Sense Resistor Value.
To ensure accurate current measurement, the input voltage generated across the current sense resistor should
not exceed +/– 125 mV. For applications having very high dynamic range, it is allowable to extend this range to
absolute maximum of +/–300 mV for overload conditions where a protector device will be taking independent
protective action. In such an overloaded state, current reporting and gauging accuracy will not function correctly.
The value of the current sense resistor should be entered into both CC Gain and CC Delta parameters in the
Data Flash Calibration section of the Evaluation Software.
STEP 5: Review and Modify the Data Flash Gas Gauging Configuration, Data, and State.
• Load Select: See Table 8 and Table 9.
• Load Mode: See Table 8 and Table 9.
• Cell Terminate Voltage: This is the theoretical voltage where the system will begin to fail. It is defined as zero
state of charge. Generally a more conservative level is used in order to have some reserve capacity. Note the
value is for a single cell only.
• Quit Current: Generally should be set to a value slightly above the expected idle current of the system.
• Qmax Cell 0: Start with the C-rate value of your battery.
STEP 6: Determine and Program the Chemical ID.
Use the bqChem feature in the Evaluation Software to select and program the chemical ID matching your cell. If
no match is found, use the procedure defined in TI's Mathcad Chemistry Selection Tool (SLUC138).
STEP 7: Calibrate.
Follow the steps on the Calibration screen in the Evaluation Software. Achieving the best possible calibration is
important before moving on to Step 8. For mass production, calibration is not required for single-cell applications.
For multi-cell applications, only voltage calibration is required. Current and temperature may be calibrated to
improve gauging accuracy if needed.
Copyright © 2012, Texas Instruments Incorporated
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