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Figure 9
shows a typical status display polling with undervoltage.
Another use of the status section is to determine the reason the part has turned off the FETs. For
example, if during test the EVM has turned off the FETs but the VREG is still on, the interface might be
connected and the status polled to see what fault the device identifies.
5.4
Basic Operation With Software
The following steps are suggested for exercising more of the device features using the EVM in its default
8-cell configuration and EEPROM settings. The board is connected as shown in
timing as described in
1. Install the software.
2. Connect the USB Interface Adapter to the computer with the USB cable.
3. Remove the screw terminal blocks from J4 and J5, and save for later use. Connect the cell simulator
board to the bq77908A main board J4 and J5. Support the under side of the EVM board as the
connectors are pressed together.
Do not connect or remove the resistive cell simulator from the board with power
applied. The resistor pulldown or pullup from intermittent connections
over-stresses the device inputs.
4. Connect the 10-pin ribbon cable from the USB Interface Adapter to the EVM J3.
5. Connect an isolated power supply negative to BATT– and positive to PACK+. Adjust the voltage to
approximately 29 V.
6. Connect an approximate 15-kΩ resistor from the power supply positive to the CHGCTL terminal. This
wakes up the part; leave the resistor connected.
7. Start the software.
8. Connect a disabled load to the pack terminals.
9. Select the Polling Enable button in the software window.
10. Observe that the status values are bright green.
11. Set a current on the load within the capability of the supply and board.
12. Decrease the power supply voltage to approximately 20 V. Observe that using the load current stops,
and the UV status indicator turns red.
13. Increase the supply voltage to approximately 29 V. Observe that the UV indicator turns green.
14. Load current may not resume until the load is disabled or disconnected.
15. Increase the supply voltage to approximately 34 V. Observe that the OV status indicator turns red.
16. Decrease the power supply voltage to approximately 29 V. Observe that the OV indicator turns green.
17. Disable polling.
18. Disable the load
19. Set the supply to 0 V, and turn off equipment.
5.5
Operation With Other Interfaces or Hosts
The bq77910 GUI software does not support other interfaces.
SLUU854 – February 2012
Submit Documentation Feedback
Figure 9. Polling Status With Undervoltage Condition
Section 5.3
will be incorrect.
Copyright © 2012, Texas Instruments Incorporated
CAUTION
bq77908AEVM Evaluation Module
Software Operation
Figure
3. Remember that
17
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