BQ79656EVM-021: Related to changes need to be done for using 12 cells instead of 16 cells.

Abhaya,

You can find the hardware changes in section 10 of the datasheet. Here is the relevant diagram:

You can propagate this pattern of floating pins for the four cells you are not using.

For software changes, you need to change the register, ACTIVE_CELL (0x0003), to the relevant number of cells you are using. 

Regards,

Ben

Abhaya,

According to section 2.3 of the EVM User's Guide, to use the EVM in the 12 cell count configuration, you must populate R24, R28, R22, R26, R21, R23, R25, and R27 with 0 Ohm resistors. 

Regards,

Ben

Abhaya,

First you must short the marked resistors. This is what we mean by populating them with a 0 Ohm resistor.

This is a BQ79616 EVM, it should be very similar to the BQ79656. In your final system you can follow the schematic in the EVM User's Guide to replicate these shorts.

Next, when you use the BQAutoEval program you need to push the "VIEW POLL SETTINGS" button on the Cell Monitor page after waking and auto-addressing the devices to change the number of cells

This causes the GUI to change the register ACTIVE_CELL[NUM_CELL] in the device to tell it to ignore the readings it gets from the shorted cells.

Regards,

Ben

Abhaya,

The GUI is not mandatory. Those instructions were only there in case you were using it. The only software changes you must make is to change ACTIVE_CELL[NUM_CELL] to 12 cells by writing 0x06 to register 0x0003. 

As detailed in section 4.1.2 of the EVM user's guide, in order to use the J15 connector and a battery pack with the EVM you must OPEN all of the switches on S1 and S2 and short the unused connections to the top cell. This means you will have to connect the test points for cells 12-15 to the test point for cell 16 or you can connect pins 16-19 of J15 to pin 21 of J15. 

Regards,

Ben

Abhaya,

The same things need to be updated. You need to continue shorting the resister ladder down to cell 6. On the EVM, convenient spots for 0 Ohm resisters are no longer provided, but this should not be a problem in the final design. You need to set ACTIVE_CELL[NUM_CELL] to 0x00 to tell the device to only read 6 cells. Additionally, you need to short the unused connected to the top cell, continuing the method described above.

Regards,

Ben