Calibration Screen
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The configuration information of the bq28400 and module calibration data also is held in the bq28400 data
flash.
The bq28400 allows for an automatic data flash export function, similar to the SBS Data logging function.
This feature, when selected via | Options | Auto Export |, exports data flash to a sequential series of files
named as FilenameNNNNN.gg where N = a decimal number from 0 to 9.
The AutoExport interval is set under the | Options | menu with a minimum value of 15 s. The AutoExport
filename also is set under the | Options | menu.
When a checkmark is next to | AutoExport |, the Auto Export is in progress. The same menu selection is
used to turn on / off AutoExport.
NOTE:
If the data flash screen is blank, the bqEVSW version in use may not support the bq28400
in use. An upgrade may be required.
9
Calibration Screen
9.1
How to Calibrate
Before calibrating the bq28400, do the following:
•
Connect a load to Pack– and Pack+ that draws approximately 2 A, and measures discharge current to
use the FETs. Connect a current source to Batt–(1N) and Pack– to calibrate without using the FETs by
forcing current through the sense resistor directly.
•
Measure individual cell stack voltage from Batt–(1N), to Cell1(1P), Cell1+2(2P).
•
Measure the temperature of the pack.
These steps may not be required, depending on the calibration type.
NOTE:
Voltage calibration with cells attached requires special consideration. Cells must be in a
resting state.
9.2
To Calibrate the bq28400
1. Select the types of calibration (see
).
2. Enter the measured values for the types selected.
3. If Voltage Calibration is selected, enter the number of cells on the pack, and individual cell voltage.
4. For Temperature Calibration, select the sensor that is to be calibrated and enter the actual
temperature. Select Calibrate Voltage and Temperature to start calibration.
5. For CC offset, board offset, and pack current calibration, use Continue Calibrations on the second
page or click the Current tab.
6. Do not apply any load current for CC offset and board offset calibration.
7. For pack current calibration, apply a 2-A current between PACK+ and PACK–. Ensure the CHG/DSG
FETs are on. Alternatively, apply the load current between Cell– and PACK–. This will force the current
through the sense resistor and allow the FETs to remain off. This is a more accurate current calibration
than applying current through PACK+ and PACK–.
9.3
Pack Calibration
Pack Calibration calibrates the voltage of the PACK pin. This is optional, because the accuracy of PACK
voltage is not required. The voltage reading is used for the gas gauge to sense the presence of a charger.
Make sure Voltage Calibration has been performed for the pack. If Voltage Calibration is not performed,
then Pack Calibration calibrates incorrectly.
Apply a known voltage between PACK+ and PACK–. Enter the actual voltage in the textbox.
Click Calibrate Pack Voltage.
16
bq28400EVM-001 SBS 1.1 Compliant Tablet PC and Netbook 2-Series Cell
SLUU494 – February 2011
Li-Ion Battery Gas Gauge and Protection
© 2011, Texas Instruments Incorporated
